Durability of Building Materials and Components for Sustainability : Scipedia

Tuning the incompatibility between recycled plastic aggregates and cement matrix with polymer-nano silica hybrids
Q. Zeng, A. Al-Mansour

DBMC 2023.

Abstract
Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental benefits. However, the soft plastics and rigid cement matrix can naturally induce the great aggregate-matrix incompatibility, which results in the degradation of engineering properties of cement-based materials containing recycled plastic aggregates (RPAs). To overcome this shortage, this work reports a strategy of tuning the cement matrix with polymer-nano silica (P-nS) hybrids. Ethylene vinyl acetate (EVA) and recycled polypropylene (PP) were selected as the coating polymer and RPA, respectively. Density, strength, water sorptivity and carbonation resistance were measured to assess the physical and mechanical properties of the mortars with recycled PP particles. Microstructure was analyzed using scanning electron microscopy (SEM) with backscattered electron (BSE) and energy-dispersive X-ray spectroscopy (EDS). Results showed that the addition of P-nS hybrids into cement decreases density, mitigates strength reduction, obstructs water sorption, but have positive and negative effects on carbonation resistance of the cement mortars with RPA. The P-nS hybrids build the organic–organic links between the cement matrix and RPA, and coordinate their deformations. The findings of this work proof the proposed strategy of tuning the compatibility between soft aggregates and rigid matrix with the engineered microstructure towards enhancing the recyclability of waste plastics in construction materials.
Abstract
Use of recycled waste plastics as the aggregates in construction materials has attracted increasingly gained attention for sustainable construction industry with great environmental [...]
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Recycling of Polypropylene Fibre Reinforced Concrete: Use of Recycled Aggregate and Recovered Fibre in New Concrete
G. Liu, N. Tošić, A. de la Fuente

DBMC 2023.

Abstract
The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete (PPFRC) in new concrete production. The mechanical properties were compared between a parent concrete, polypropylene fibre reinforced recycled aggregate concrete (PPRAC), and recovered polypropylene fibre concrete (Re-PPRFC). All concretes were designed to have the same compressive strength and slump. The parent concrete was produced with 9 kg/m3 of polypropylene fibre. After recycling, the RA and RF were collected and new concretes with RA and RF, PPRAC and PPRFC, respectively, were produced with the same fibre content as the parent concretes. The strain-stress relationship in compression and residual tensile strength were tested. The results obtained for PPFRC, PPRAC and rePPRFC were compared. The results show that the RA and RF obtained by PPFRC recycling can benefit new concrete production.
Abstract
The study aims at investigating the feasibility of using recycled aggregate (RA) and recovered fibres (RF) obtained from recycling of polypropylene fibre reinforced concrete [...]
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Numerical Simulation on the Influences of Wind Pressure on Jet Characteristics of Shotcrete
S. Zhang, Y. Zhang, K. Wu, X. Kong

DBMC 2023.

Abstract
A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding with a wall based on computational fluid dynamics theory, in which concrete was regarded as a Bingham fluid. The influences of wind pressures、 pumping speeds、 air incident angles and rheological parameters on five characteristic parameters including spouting velocity, jet velocity, jet trajectory, collision velocity and distribution of shotcrete on the wall were analyzed in depth. Results showed that concrete was gradually mixed well with air in the nozzle with an increasing average velocity, and the increase of velocity was most pronounced in the contraction section of nozzle. With the increases of wind pressures and pumping speeds, the spouting velocity and spouting mass of concrete both increased. Higher wind pressure and pumping speed led to larger jet velocity and more concentrated distribution, resulting in significantly longer jet distance, higher collision velocity and larger distribution area. The collision velocity and volume fraction of concrete on the wall were distributed symmetrically along Y axis, shifting towards the direction of gravity. With the increases of air incident angles, the spouting velocity and spouting mass of concrete both decreased, the shifting to gravity is weakened and the volume fraction decreased first and then increased. When plastic viscosity decreased, the spouting velocity and spouting mass of concrete both increased, accompanying with a higher jet velocity, a longer spraying distance and a larger distribution area.
Abstract
A gas-liquid two phases model of shotcrete was developed to simulate the whole process from the spouting of concrete from nozzle, the scattering in the flow field to its colliding [...]
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Effect of Pre-calcination of Lead-zinc Tailings on the Activation of Blast Furnace Slag
J. Ou, Z. Luo, Y. Mu

DBMC 2023.

Abstract
Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs were pre-calcined at different temperatures and then explored whether it is capable of being the activator of slag. The effects of pre-calcination on the phase composition of LZTs were elucidated by XRD. The compressive strength of LZTs-activated slag pastes was investigated, and the mineral composition and microstructure of the pastes were detected by XRD and SEM. The results imply that with the elevating of heating temperature from 500 ℃ to 1000 ℃, the dolomite in LZTs decompose into CaO and MgO, and the oxidation of pyrite resulted in the formation of Fe2O3 and gaseous SO3, then SO3 reacted with a part of formed CaO to produce CaSO4. The resulting CaSO4 and CaO can become the sulfate activator and alkaline activator of slag, respectively. The LZTs-activated slag pastes prepared with the LZTs preheated at 800 ℃ exhibit the highest strength at 90 d, which yield 24 MPa. The hydration products of LZTs-activated slag were ettringite and calcium silicate hydrates (C-S-H gel). Large amounts of dense C-S-H gel bond together, connecting most of the ettringite networks into a whole, thus forming a dense structure and effectively improving the strength of LZTs-activated slag. The outcome of this study provides a potential disposing or reusing approach of the large amounts of LZTs.
Abstract
Blast furnace slag and lead-zinc tailings (LZTs) are solid wastes from the iron-making and mining industries, respectively. In order to reuse these solid wastes, the LZTs [...]
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Probability Durability Assessment of Existing Concrete Structures in Carbonation Environment
H. Gu, J. Yao, Z. Meng

DBMC 2023.

Abstract
In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. This paper presents a methodology for assessing the probability durability of existing structures, taking into account the nondestructive testing results and the target reliability index. The initial step involves introducing a correction coefficient into the carbonation and corrosion development theory model. This coefficient is necessary to account for the correction associated with the corrosion monitoring of steel. The values of this coefficient should be determined based on the actual testing results, specifically considering the presence of reinforcing steel corrosion. Next, a probability expression is proposed using the measured results of probability characteristics and the target reliability index. This approach takes inspiration from the design-value method and the existing theory of structure reliability. It also takes into account the specific variables of concrete protective cover thickness and the compressive strength as the fundamental random variables. The residual working life can be calculated as the outcome of a durability assessment through quantitative analysis. This calculation can serve as a valuable reference for the maintenance program.
Abstract
In a particular service environment, the calculation models used to determine the durability of existing concrete structures differ from those employed in the design phase. [...]
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Overview on Testing Method of Internal Damage to Special-shaped Stone Components in Palace Museum
Y. Qian, F. Qi, K. Niu

DBMC 2023.

Abstract
Irregular historic stone components are very important parts of the ancient architecture in the Palace Museum. They have been subjected to deteriorations from surface to interior under the combined effects of many factors such as wetting and drying, salt dissolution and recrystallization, selfload, external load, and environment action. The internal damages in these stone components are difficult to detect but are crucial for the assessment of the intact of these components. In order to detect the internal damage of stone components, especially the special-shaped stone components, which cannot be tested by comment methods. Taking evaluation on preservation status of stone components in a qualitative and quantitative way， with application of ultrasonic computerized tomography and regular inspection, a convenient, safe, economical, efficient, and readable method for detecting the internal damage of irregular stone components can be established in order to detect any safety hazards as early as possible and provide data support for assessment and conservation, achieving a better preventive conservation.
Abstract
Irregular historic stone components are very important parts of the ancient architecture in the Palace Museum. They have been subjected to deteriorations from surface to interior [...]
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Evaluating the Future Moisture Performance of the Stucco-Clad Wall Assembly in Selected Canadian Cities
O. Zhe, X. Xiao, H. Ge, M. Lacasse

DBMC 2023.

Abstract
Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed to such climate could experience a higher moisture load than in the past, which could have a negative impact on its performance in the long run. The stucco-clad wall assembly, which has been widely employed in the construction of low-rise residential buildings throughout Canada may not be adequately designed to be resilient to the future climate. Thus, in the study described in this paper, the future moisture performance of the stucco-clad wall assembly located in two Canadian cities with different levels of moisture load, i.e., Vancouver and Calgary, subjected to projected future climate is investigated. The analysis includes two phases: conducting watertightness for a full-scale stucco wall specimen to determine the relationship between the climate data and the moisture load in the wall assembly and implementing hygrothermal simulations using the relationship obtained from the watertightness test for the performance assessment. Mould growth index at the exterior surface of the oriented strand board of stucco-clad wall assembly for the historical and projected future time periods is compared and discussed.
Abstract
Due to climate change, it is expected that the amount of precipitation in most parts of Canada will increase in the coming decades. Consequently, the building envelope exposed [...]
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Analysis of Thermal Bridges in Concrete and Cross-Laminated Timber (CLT) Constructions: A Numerical Study
A. Zegeye, F. Tariku

DBMC 2023.

Abstract
The thermal efficiency of a building envelope relies on various factors, including insulation resistance, continuity, the thermal conductivity of structural materials, and the presence of thermal bridges. This study focuses on studying the thermal performance of thermal bridge details in two construction types: concrete and Concrete and Cross-Laminated Timber (CLT). For the study, two common building envelope details with significant thermal bridges are considered, balcony and intermediate wall-to-floor connections. Utilizing the finite element program COMSOL Multiphysics, hourly transient simulations were conducted over a one-year period to assess the heat loss/gain associated with thermal bridges, considering daily, seasonal, and annual heat flow for two diverse climatic conditions (hot weather Houston-Climate Zone 2 and cold weather Toronto-Climate Zone 6). The findings demonstrate that thermal bridges constructed from CLT outperformed those made of concrete. In Toronto, the annual heat flow for the concrete balcony was 146% higher compared to CLT, while in Houston, it was 67% higher. However, this trend was significantly reduced for the wall-to-floor detail, with a concrete detail showing a 13% increase in heat flow for Toronto and a 7% decrease in annual heat flow for Houston. Furthermore, the dynamic analysis revealed notable heat flow magnitude changes in the balcony detail, highlighting the importance of thermal conductivity, while the wall-to-floor detail exhibited dampening fluctuations in heat flow, emphasizing the material's heat capacity importance in this context.
Abstract
The thermal efficiency of a building envelope relies on various factors, including insulation resistance, continuity, the thermal conductivity of structural materials, and [...]
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Use of Machine Learning in Processes Optimization for Drinking Water Treatment Plant Butoniga (Istria, Croatia)
G. Volf, S. Zorko, I. Čule

DBMC 2023.

Abstract
Drinking water treatment plant Butoniga is located in central Istria (Croatia) downstream of the Butoniga reservoir. The Butoniga reservoir is an artificial lake created in 1987 with two main objectives: 1) protection from adverse water impacts, and 2) drinking water supply. The operation of the drinking water treatment plant is mainly related to the tourist season, and the 5.000.000 m3 of produced and distributed drinking water annually, 3.000.000 m3 is produced and distributed during June 15 to September 15, when the raw water quality in the Butoniga reservoir is the worst. Regarding this, main problem with Butoniga reservoir and thus drinking water treatment plant appear in summer months when water temperature is the most critical parameter and raw water for the treatment process must be captured from the lowest layer of the reservoir which have increased concentrations of Mn, Fe, NH4 and lower pH values and thus influence on the treatment processes. To deal with this problem, model predicting Mn, seven days in advance is build using machine learning approaches. Build model have high accuracy compared to the measured data, with a good prediction of the peak values. As such, obtained model can help in optimization of the treatment processes which are depending on the quality of raw water, and overall, in sustainability and management of the drinking water treatment plant Butoniga.
Abstract
Drinking water treatment plant Butoniga is located in central Istria (Croatia) downstream of the Butoniga reservoir. The Butoniga reservoir is an artificial lake created in [...]
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Proposal of Soundness Index for Existing RC Apartment Building for Proper Management Through Visual Monitoring
N. Tsuchiya, N. Mishima, K. Nemoto, K. Matsuzawa, K. Nakada, T. Kage, H. Tanano

DBMC 2023.

Abstract
A numerical index for housing complexes of reinforced concrete maintained properly was proposed. First, based on the literature review, deterioration grade and a method for evaluating soundness for RC housing complexes, which determined by visual inspection, was proposed. And then, accelerated deterioration experiments of small RC wall and investigation of existing buildings were conducted. From the study, a correlation between the deterioration grade determined visually and rebar corrosion grade was confirmed. By using building health H(t), that is proposed as index of soundness for existing RC housing complexes, RC housing complexes whose age were 46 to 69 years were evaluated. From the study, it was confirmed how much deterioration the evaluation value indicates.
Abstract
A numerical index for housing complexes of reinforced concrete maintained properly was proposed. First, based on the literature review, deterioration grade and a method for [...]
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Effect of Moderately Elevated Temperatures on Performance of Portland Cement Concrete
S. Gao, M. Liu, Q. Kong, K. Li

DBMC 2023.

Abstract
High temperature is one of the critical factors leading to the change in concrete performance since it affects the physical structure and chemical components of concrete. However, some concrete structures are continuously subjected to moderately elevated temperatures (typically less than 200 ℃) when operating, such as chimneys for the metallurgical industry and structures in nuclear power plants. The deterioration process of these structures could be caused and accelerated by a high-temperature environment. Thus, the safety and performance of these concrete structures at elevated temperatures during service life are crucial. This paper aims to investigate the change in concrete performance exposed to sustained moderately high temperatures. The concrete cured for 56 days was subjected to temperatures ranging from 65℃ to 200 ℃ for 28 days. The mechanical properties of concrete at different heating temperatures were tested, including compressive strength, splitting tensile strength and modulus of elasticity. Meanwhile, concrete’s durability after heating was evaluated using the concrete electrical resistivity test. The concrete elevated-temperature performance was compared to identical concretes at room temperatures, and the evolution of each property was analyzed. Based on experimental results, the long-term performance of concrete in a moderately elevated temperature environment is predicted.
Abstract
High temperature is one of the critical factors leading to the change in concrete performance since it affects the physical structure and chemical components of concrete. [...]
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Heavy Metals Immobilization Property and Mechanisms of LDHs-modified Cementitious Materials
L. Chi, C. Huang

DBMC 2023.

Abstract
Layered double hydroxide (LDH) has a positive effect on the adsorption and immobilization of heavy metals. The compressive strength and the heavy metal ions Pb2+ immobilization of CaAl-LDH modified cement paste were studied in this paper. Through research, it was found that compared with the cement paste sample with a Pb2+ content of 1% after curing for 7d and 28d, the addition of CaAlLDH to the cement paste sample increased the compressive strength by 6.1% and 1.6%, respectively, demonstrating the enhancing effect of CaAl-LDH on the strength of cement paste. Compared with the sample containing only Pb2+, the addition of CaAl-LDH to the cement increased the immobilization rate by 0.3% after 12 hours of leaching time and showed varying degrees of improvement at different leaching times. The immobilization mechanism of heavy metals in LDH blended cement paste was revealed by microstructure characterization. It was founded that Pb2+ can replace Ca2+ in AFt, AFm, and LDH, and can co-precipitate with OH-.
Abstract
Layered double hydroxide (LDH) has a positive effect on the adsorption and immobilization of heavy metals. The compressive strength and the heavy metal ions Pb2+ immobilization [...]
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Chemo-physical Analysis on Corrosion Initiation of Offshore Structures under Chloride Attack
B. Dong, Y. Yu, W. Gao

DBMC 2023.

Abstract
Chloride ingress has been recognized as a main factor inducing the corrosion of offshore reinforced concrete structures. It is acknowledged that the chemical attack can lead to concrete property deterioration, which inevitably affects the reinforcement corrosion. Herein, the influence of the concrete aging on the chloride-induced corrosion initiation is systematically evaluated by a novel numerical framework. In this framework, the chemo-physical analysis is conducted based on coupled NernstPlanck model and Gibbs energy minimization model. The proposed method is first validated against reported experimental results. It is found that the chloride ingress is always accompanied by leaching of hydrates near the exposure surface, leading to the porosity enlargement. Moreover, due to chemical binding of chloride to monosulfoaluminate, ettringite continuously precipitates under the function of released sulfate ions. Through a series of numerical analyses, it is revealed that the newly formed hydrates impose competitive effects on chloride transportation due to the simultaneous pore-clogging and expansion-induced microcracks. Chloride-induced corrosion occurs earlier in the situation that the effect of microcracks overcomes that of pore clogging, otherwise, the corrosion is delayed.
Abstract
Chloride ingress has been recognized as a main factor inducing the corrosion of offshore reinforced concrete structures. It is acknowledged that the chemical attack can lead [...]
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Carbonation-induced Early Corrosion Propagation Based Service Life Assessment Model (CECP-SAM)
L. Chen, R. Su

DBMC 2023.

Abstract
Supplementary cementitious materials (SCMs) are widely used for sustainable concrete. However, this is challenged due to the deteriorated resistance towards carbonation-induced corrosion. This paper introduces the establishment of a novel carbonation-induced early corrosion propagation based service life assessment model (CECP-SAM). This model is characterized by considering the early corrosion propagation (incipient cracking) and the use of supplementary cementitious materials. Based on experimental and numerical methods, the effects of binders, water/binder (W/B) ratio, exposure condition, cover thickness, rebar diameter, semi-carbonation zone, cathode-anode ratio on service life are investigated by CECP-SAM. The model is justified by using the results from a field investigation in Hong Kong. Performance-based service life equations are also given based on CECP-SAM.
Abstract
Supplementary cementitious materials (SCMs) are widely used for sustainable concrete. However, this is challenged due to the deteriorated resistance towards carbonation-induced [...]
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Service Life Prediction of Concrete Against Freezing and Thawing Based on Water Absorption Results
L. Xu, J. Wang, C. Zhang, Z. Li, Q. Yang

DBMC 2023.

Abstract
Freezing and thawing resistance performance of concrete is a critical issue when evaluating the durability performance of concrete. This paper aims to predict the freezing and thawing resistance performance of concrete based water absorption indexes, meanwhile, five groups of experiments on porosity, short-term water absorption, long-term water absorption, MIP and pore structure scanning were respectively carried out for concrete. According to the experimental results, the important indexes such as porosity, water absorption, gas content and bubble spacing coefficient were obtained, which provided the basis for the prediction of durability and service life. The concept of equilibrium time ratio is introduced to simplify the calculation process. Based on the critical saturation theory, the service life of concrete against freezing and thawing is predicted by combining the environmental parameters and the indexes measured in experiments. The calculated results verified that the freeze-thaw durability life of air-entrained concrete is significantly increased compared with that of concrete without air-entrained concrete. In addition, a wide range of the service life was predicted for the 5 mixes, and the results could provide a guidance for selecting a proper mix design of concrete subjected to freezing and thawing.
Abstract
Freezing and thawing resistance performance of concrete is a critical issue when evaluating the durability performance of concrete. This paper aims to predict the freezing [...]
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Microstructure of Cement Paste with Expansive Additives under Free and Restrained Conditions
M. Gupta, G. Igarashi, Y. Takahashi, T. Ishida

DBMC 2023.

Abstract
Expansive additives (EAs) have been widely used to reduce the risk of cracking due to shrinkage. Such additives cause early age expansion of concrete due to the formation of Portlandite and Ettringite in the pores of the cement paste, which affects the cement paste's microstructure. The presence of external restraints in the form of reinforcement and support affects the expansion and, ultimately the microstructure of cement paste. In the current study, the microstructure of cement paste with expansive additives is studied using mercury intrusion porosimetry (MIP). A free lime-based EA, with 10 and 15% (by weight) cement replacement ratios, is studied in the current study. The porosity and pore size distribution of the cement paste with EA were studied under free and restrained conditions. Results show that the under the stress-free condition, the porosity of the paste increased, while under the restrained condition, the porosity remained much similar to the reference case of OPC. Further, the pore size distribution of the cement paste with EA under free and restrained conditions is explained, and the effect of EA and restraint on the microstructure is discussed.
Abstract
Expansive additives (EAs) have been widely used to reduce the risk of cracking due to shrinkage. Such additives cause early age expansion of concrete due to the formation [...]
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Study on Release Performance of Concrete Release Agent
S. Lu, Z. Jie, W. Liya, Y. Maoqian, L. Tongwei

DBMC 2023.

Abstract
In this paper, the effects of types of concrete release agent, the amount of brushing per unitarea and the 1d's strength of concrete on the release performance were studied. The adhesion and filmforming ability of O/W emulsion release agent was improved by adding high polymer. The results showthat the 1d's strength of concrete has no effect on the release performance of the release agent. The mostimportant factors affecting the release performance are brushing amount per unit area and the type ofrelease agent. O/W emulsion release agent with polyacrylamide and polyethylene glycol all stick mold. The more they are added, the heavier the stickiness is. While, the release performance with polyethyleneglycol is very close to blank sample.
Abstract
In this paper, the effects of types of concrete release agent, the amount of brushing per unitarea and the 1d's strength of concrete on the release performance were studied. [...]
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Properties of Mineral Powders Modified Foamed Concrete
Q. Liu, H. Chen

DBMC 2023.

Abstract
In order to improve the stability of lightweight foamed concrete, the particle-stabilized foam (PSF) has been proposed because of its high stability. However, most PSFs added particles to foams, and few researchers have investigated whether the stabilization effect exists when particles are added to the paste. In this study, a new type of foamed concrete was prepared by adding different kinds of mineral powders to cement and using ionic surfactants to prepare foam. The influence of different mineral powders on the mechanical properties and durability of foamed concrete was investigated. Results showed that mineral powders decreased the drainage and disproportionation of foam, which stabilizes the foam. The excellent stability is attributed to the interaction between the mineral powders and ionic surfactants, which allows the mineral powders to adhere to the foam surface and form a dense granular film layer. Moreover, due to the interaction between mineral powders and ionic surfactants, hardened foamed concrete has a robust pore structure, which improves its properties.
Abstract
In order to improve the stability of lightweight foamed concrete, the particle-stabilized foam (PSF) has been proposed because of its high stability. However, most PSFs added [...]
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Influence of Alkali-resistant Glass Fibers Distribution on Properties of Cementitious Composites
B. Mrduljaš, A. Pranjić, M. Štefančić, K. Didulica, A. Baričević

DBMC 2023.

Abstract
The waste hierarchy establishes a prioritized framework for effective waste management, where higher levels such as prevention, re-use, and recovery are associated with the conservation of primary resources and the retrieval of secondary resources. This approach aligns with the objectives of the construction industry, which aims to promote the efficient utilization of resources by treating raw materials in an environmentally responsible manner. In this context, utilizing waste fibers to reinforce cementitious composites becomes more logical than producing new fibers with similar properties. These waste fibers typically originate from the production of high-performance technical textiles used for structural repair and rehabilitation. By reusing these waste materials, the construction industry contributes a circular economy in its own sector and fosters cross-sectoral industrial symbiosis. Although the potential benefits and positive environmental impact of utilizing such materials are recognized, their influence on the properties of composites requires further investigation. This study examines the impact of production waste glass fibers on the properties of the mortar in both the fresh and hardened states. The study focusses on properties such as compressive strength and toughness. To gain a better understanding of the fibers’ contribution to the matrix properties, an investigation was conducted using µCT. The study focuses on investigating the effects of waste fibers with lengths of 5 and 10 mm and different dosages (0.2, 0.6 vol.%) on the properties of high-strength mortar, comparing them with factory fibers.
Abstract
The waste hierarchy establishes a prioritized framework for effective waste management, where higher levels such as prevention, re-use, and recovery are associated with the [...]
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Study on Natural Passivation Behavior of Corrosion-resistant Steel Rebars in the Mortar
G. Liu, D. Zhang, H. Chen, Z. Fan, Q. Wu

DBMC 2023.

Abstract
The passivation behavior of HRB400 carbon steel rebar, 304 austenitic stainless steel rebar and 2304 austenitic-ferritic duplex stainless steel rebar during curing stage of mortar was studied by electrochemical testing techniques such as open-circuit potential, electrochemical impedance spectroscopy and linear polarization curve, and the corrosion resistance of the passivation film of the three rebars was compared to provide a reference for the practical engineering application of corrosion-resistant steel rebars. The study shows that all three types of steel rebars can be passivated during the 28 days curing stage of mortar, and 2304 duplex stainless steel rebars have the best passivation film corrosion resistance, followed by 304 stainless steel rebars, and HRB400 steel rebar was the worst.
Abstract
The passivation behavior of HRB400 carbon steel rebar, 304 austenitic stainless steel rebar and 2304 austenitic-ferritic duplex stainless steel rebar during curing stage of [...]
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Property and Environment Evaluation of Cement Replaced with Treated Reclaimed Concrete Slurry Waste
R. Jun, X. Yunqiu, L. Birunxuan, Z. Ji, L. Min

DBMC 2023.

Abstract
The development of the cement industry consumes piles of natural resources and generating huge amount of waste and causing serious pollution, which can be partially solved by replacing with other cementitious materials, in particularly, solid waste. Reclaimed concrete slurry waste (RCSW), a corrosive and hazardous the residues from the reclaimed system for retrieving the aggregates from the returned concrete or cleaning the concrete mixer and trucks in the ready-mixed concrete plant, could that cannot be used to manufacture reclaimed concrete. However, the pre-hydration limits the hydraulic property of RCSW, which requires the proper treatment. This paper investigated the effect of three different treatment methods in improving the performance of RCSW and its feasibility of replacing cement under different substitution ratio in manufacturing reclaimed concrete. The treatment included sieving, shearing and ball-milling, and the substitution ratio was set as 15%, 30% and 45%, respectively. In addition to compressive strength and hydration properties, the environment impact of the cement paste replaced with RCSW were investigated as well. The results showed that compared within three methods, the shearing and ball-milling generated the treated RCSW with smaller particle size and high roundness. For the RCSW substituted cement paste, the substitution with 15% of treated RCSW provided the highest strength, meanwhile, while at a higher substitution ratio significantly reduced the compressive strength. The 15% of ball milling treated RCSW produced more products during the hydration process, resulting in a denser structure. According to the economic and environmental calculations, RCSW substitution reduced CO2 emissions, in which, the ball-milling method showed a lower carbon footprint.
Abstract
The development of the cement industry consumes piles of natural resources and generating huge amount of waste and causing serious pollution, which can be partially solved [...]
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Oxygen Diffusion Property of Fatigue Damaged Concrete under Drying-wetting Cycle
J. Zhilu, H. Sheng, F. Chuanqing, Y. Wenjie

DBMC 2023.

Abstract
Oxygen diffusion has an important influence on the corrosion process of reinforced concrete structures. In the marine environment, concrete is subject to both fatigue loads and periodic drying-wetting conditions. In this study, the oxygen diffusion performance of damaged concrete due to fatigue is studied under drying-wetting cycle condition, which is of great significance to the development of concrete durability theory. The pore structures of concrete specimens with different damage degrees after drying-wetting cycle were measured by nuclear magnetic resonance (NMR). The effects of drying-wetting cycle and damage degree on pore structure were studied, and the oxygen diffusivity of damaged concrete before and after drying-wetting cycle was compared and analyzed. The results show that the pore size distribution curves of concrete specimens move to the smaller pores and the peaks decrease after 28 days of drying-wetting cycle. The proportion of gel pores (< 10 nm) increases and the proportion of medium and large capillary pores (10 - 1000 nm) decreases. After the drying-wetting cycle, the porosity of the damaged concrete specimens all decreased to certain degrees. It shows that the microstructure of the specimen is improved and the internal structure of concrete becomes more complex in the early stage of drying-wetting accelerated erosion. After the drying-wetting cycle, the oxygen diffusivity of all concrete specimens decreased, and the oxygen diffusivity of undamaged concrete decreased the most, about 10 times, but with the increase of damage degree, the reduction effect generally decreased.
Abstract
Oxygen diffusion has an important influence on the corrosion process of reinforced concrete structures. In the marine environment, concrete is subject to both fatigue loads [...]
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Optimal Amorphous Oxide Ratios and Multifactor Models for Binary Geopolymers from Metakaolin Blended with Substantial Sugarcane Bagasse Ash
L. Jing, T. Ye

DBMC 2023.

Abstract
As a potential precursor, the utilization of sugarcane bagasse ash imparts enormous technical and environmental benefits to human society. However, its rich crystal content challenges the mix design of sugarcane bagasse ash-involved geopolymers. The present study is aimed to contribute toward the substantial utilization of sugarcane bagasse ash in geopolymers and develop a guideline for designing binary geopolymers from metakaolin and sugarcane bagasse ash. The experimental results show that when suitably designed, the compressive strength of metakaolin-sugarcane bagasse ash geopolymers satisfied the structural use in building engineering, and the sugarcane bagasse ash proportion could substantially reach up to 50%. Moreover, through a combination of mechanical, economic and environmental assessments, the optimal mixing proportions fall into the following ranges: SiO2/Al2O3=4.63~5.60, Na2O/Al2O3=1.5~2.0 and H2O/Na2O=8~10. Further, multi-factor models are proposed to regulate the mix design of binary geopolymers, with a R2 value beyond 0.9 .
Abstract
As a potential precursor, the utilization of sugarcane bagasse ash imparts enormous technical and environmental benefits to human society. However, its rich crystal content [...]
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Negative Emission Potentials Using Biogenic Building Materials - A Case Study from Denmark
R. Torben Valdbjorn, T. Emil Engelund, B. Niclas Scott, N. Thomas, J. Uffe, B. Annette, G. Stefan Christoffer

DBMC 2023.

Abstract
Significant reductions in carbon footprint can be achieved by increasing the use of biogenic materials in construction. In biogenic materials, carbon is embedded as long as the materials are not biologically degraded, and they consequently act as carbon reservoirs that keep CO2 out of the atmosphere. The reservoirs of carbon are maintained if the biogenic materials during maintenance and renovation are replaced by similar ones. Buildings containing more wood, straw, and other biogenic materials and less concrete, steel, and mineral wool are therefore part of the way forward for a sustainable restructuring of the construction industry. Until now, the main focus has been on reducing energy consumption of buildings, while less focus has been on energy consumption and the climate impact from the production of materials and the construction process itself. This paper examines the potential carbon reservoir in the building stock in Denmark for the next 100 years. In detail the paper describes potential building components made from biogenic resources, outlines the necessary amounts and qualities of biogenic materials, and summarizes the available biogenic resources. The article is based on the conditions for construction in Denmark and the opportunities Denmark has as an industrialized agricultural country with a long coastline, which can be utilized in the production of biogenic resources for manufacturing of building materials.
Abstract
Significant reductions in carbon footprint can be achieved by increasing the use of biogenic materials in construction. In biogenic materials, carbon is embedded as long as [...]
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Molecular Dynamics Study between Amine Solution and Calcium Hydroxide
T. Pan, R. Kitagaki, Y. Yoda

DBMC 2023.

Abstract
Carbon dioxide can be captured by amines and carried into calcium hydroxide to generate calcium carbonate. In this study, molecular dynamics simulations were performed to study the interaction energy and structure between amine solution and calcium hydroxide crystal slab at the molecular level. MDEA was chosen as a representative amine. According to the one-dimensional concentration function, it was found that at a low ratio of MDEA, it was preferentially distributed close to the calcium hydroxide. And as the content in the solution increased, MDEA was gradually distributed equally throughout the aqueous solution. Compared to water, the interaction energy between MDEA and calcium hydroxide is greatly reduced and gradually decreases with increasing amine content. This means that the interaction between the two is reduced, and the reaction is more difficult to occur. In addition, the system of carbon dioxide dissolved in a solution of amine and water was simulated. The distribution of carbonate and bicarbonate was found to be relatively uniform at MDEA ratios of 5% and became irregular above 20%.
Abstract
Carbon dioxide can be captured by amines and carried into calcium hydroxide to generate calcium carbonate. In this study, molecular dynamics simulations were performed to [...]
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Laboratory and Pilot Investigation on Properties of precast Engineered Cementitious Composites (ECC) Subjected to Carbonation Curing
Z. Duo, E. Brian R., L. Victor C.

DBMC 2023.

Abstract
The concrete industry is facing an increasing challenge for sustainability. Besides the large embodied carbon, the intensive operational carbon associated with repetitive repair becomes the main hurdle for lifecycle emission reduction. In this study, the feasibility of sequestering CO2 into durable engineered cementitious composite (ECC) through early-age carbonation curing was investigated. The goal is to demonstrate a simultaneous reduction of the material’s embodied carbon (by CO2 sequestration) and lifecycle emissions (by ECC’s superior durability). The material was processed at both lab and pilot scales and was demonstrated on precast pedestrian pavement slabs. Results show that ECC was highly reactive to CO2 at lab scale, with 26.5% CO2 uptake by cement mass after 24-hour carbonation. However, the early-age carbonation was subjected to a significant size effect and attained a 4.3% CO2 uptake for pilot-scale specimens with a low specific surface area. Despite this reduction in carbonation efficiency, the calcite precipitation through carbonation curing was found to densify the fiber/matrix interface and improve the composite ultimate tensile and flexural strength by up to 28.8%. Carbonation curing also enhanced ECC’s crack width control, thus mitigating sulfate attack and lowering surface salt scaling on freeze-thaw exposure. It is suggested that producing ECC through carbonation curing is technically viable, and the carbon-sequestered ECC is recommended for small-scale precast components for enhanced durability and sustainability.
Abstract
The concrete industry is facing an increasing challenge for sustainability. Besides the large embodied carbon, the intensive operational carbon associated with repetitive [...]
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Impact of the Thaumasite Sulfate Attack on the Pore Structure and Gas Permeability of Cement Mortar
R. Bo, H. Tingyu, H. Xiaobin, L. Kefei

DBMC 2023.

Abstract
In this study, the impact of the thaumasite sulfate attack (TSA) on cement mortar was investigated by comparing it to the ettringite sulfate attack (ESA). Mortar specimens with three binders, corresponding to the blank, ESA, and TSA, were exposed to sulfate solution. The evolutions of thaumasite and ettringite formation, pore structure, and gas permeability on the mortar specimens were characterized through XRD, 1H NMR, and CemBureau device. The experimental results show that: (1) both ettringite and thaumasite were formed in TSA; (2) ESA reduces the capillary pore space, whereas TSA decreases both the capillary pore and interlayer pores; and (3) ESA decreases the gas permeability while TSA significantly increases it.
Abstract
In this study, the impact of the thaumasite sulfate attack (TSA) on cement mortar was investigated by comparing it to the ettringite sulfate attack (ESA). Mortar specimens [...]
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Fracture Process of In-situ Polymerization Modified Cementitious Materials
X. Chengji, Z. Qiang

DBMC 2023.

Abstract
By regulating cement hydration reaction and organic monomer polymerization, the strength and deformability of in-situ polymerization modified cement-based materials are greatly improved. However, the fracture processes of this type of organic-inorganic composites have not been systematically investigated. In this work, sodium acrylate (SA) monomer in-situ polymerization modified cementitious composites (iPSA) were fabricated. Three-point bending (TPB) test was conducted with digital image correlation (DIC) technique for characterizing the fracture process zone (FPZ). Microscopic test was conducted to unravel the crosslinked organic-inorganic composite structures in the iPSA matrix. Results showed that an obvious strain concentration region occurred and grew at the notch tip of the iPSA beams with load. The gradually expanding width of FPZ was normally distributed. Microscopic test suggested that the physical interlinks between the cement hydrates and sodium polyacrylate may resist again the FPZ development of iPSA. The findings of this work would deepen the understandings of fracture process of polymer modified cementitious composites with broad engineering applications.
Abstract
By regulating cement hydration reaction and organic monomer polymerization, the strength and deformability of in-situ polymerization modified cement-based materials are greatly [...]
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Evaluation of Carbonation Degree of Hardened Cement Paste with Different Water-Cement Ratio in Wet-Dry Cycle
Z. Zhao, D. Oh, Y. Wang, R. Kitagaki, T. Masuo

DBMC 2023.

Abstract
One of the global environmental problems, CO2 emissions from cement production intensifies in these decades. To solve this problem, countermeasures for CO2 emissions using waste concrete, which has ability to absorb CO2 due to contain calcium-silicate-hydrate (C-S-H) and portlandite (Ca(OH)2), are in the spotlight recently. However, considering the limited time before recycling as roadbed materials, it is important to increase CO2 absorption efficiency so that as much CO2 as possible reacts with waste concrete. In this study, hardened cement paste powders (HCPWs) with the water-to-cement ratios of 0.4, 0.5 and 0.6 were evaluated for the degree of carbonation under various humidity conditions. HCPWs were pulverized to a particle size of 0.6 to 1.18mm and put in desiccators keeping constant humidity condition of RH60 and RH80. In addition, desiccators were prepared with RH60-80 cycle (wet-dry cycle) of 30 minutes, 1 hour, 2 hours and 4 hours to determine the degree of carbonation promotion according to periodic humidity changes. The degree of carbonation of HCPWs were measured by thermogravimetric analysis (TGA). The result shows that the degree of carbonation was improved as the water-cement ratio increased, because the higher the water-to-cement ratio, the more open pores were contained. In addition, vaterite and aragonite caused by the decomposition of C-S-H were the most produced under RH60-80 cycle conditions. This is considered to be because the reaction area with CO2 was increased by weakening the C-S-H by repeating drying and wetting.
Abstract
One of the global environmental problems, CO2 emissions from cement production intensifies in these decades. To solve this problem, countermeasures for CO2 emissions using [...]
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Evaluate the Ability to Determine the Carbonation Depth of Concrete by Hyperspectral Imaging
Y. Wang, D. Oh, R. Kitagaki

DBMC 2023.

Abstract
In recent years, using concrete to absorb CO2 in the atmosphere has attracted attention as one of the global warming countermeasures. In general, destructive methods have been used to evaluate the amount of CO2 absorption in concrete buildings and civil engineering structures. However, it needs to sample a portion of the concrete, and it is impractical to conduct continuous disruptive sampling of the structures in use. Therefore, it is necessary to develop non-destructive tests to evaluate the amount of CO2 absorption in concrete. In this study, Multi-spectral imaging, which are the methods of non-destructive tests, were used to visualize the presence of calcium carbonate with depth-axis from surface of the concrete specimen which have been the preliminary drilled holes. In addition, moistened cotton swabs were used to extract the pore solution by pressing the inner wall of the hole and to test it for determination of the distribution of pH with depth. The results indicate that Multi-spectral imaging can evaluate different carbonation depths of concrete samples. Moreover, PH of each point examined in the specimens can evaluate as the depth distribution of calcium carbonate. Results were compared and discussed with each other depending on each methodological characteristic.
Abstract
In recent years, using concrete to absorb CO2 in the atmosphere has attracted attention as one of the global warming countermeasures. In general, destructive methods have [...]
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Effects of Multi-scale Siliceous additives on Hydration and Microstructure of Hardened Cement Pastes
X. Zhang, Y. Zhang, J. Zeng, K. Wu

DBMC 2023.

Abstract
Siliceous materials are commonly used in concrete with physical filling and higher pozzolanic reactivity, such as silica fume (SF) and nano-silica (NS). Investigations were conducted into the effects of SF, hydrophobic silica fume (HSF), and synthesized NS on the mechanical properties and microscopic characteristics of hardened cement pastes (HCPs). The surface of silica fume was hydrophobically modified using isooctyltriethoxysilane. Fourier infrared spectrometer (FTIR), X-ray diffractometer (XRD), and energy spectrometer (EDS) were used to evaluate the hydration, while mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were used to analyze the pore structure and microscopic morphology of HCPs. The results demonstrated that HSF has better dispersion in cement pore solution. The addition of HSF exhibits the higher pozzolanic reactivity, weakens CH diffraction peaks, generates higher levels Q3 C-S-H gels, and significantly lowers the Ca/Si ratio of C-S-H gels. Due to the hydrophobicity, HSF increases the volume of micro-pores in range of 10-100 nm, resulting in a decrease in strength. Compounding HSF and NS further weakens the CH diffraction peak, decreases the Ca/Si ratio of C-S-H gels, and reduces the micro-pore volume to refines the pore structure.
Abstract
Siliceous materials are commonly used in concrete with physical filling and higher pozzolanic reactivity, such as silica fume (SF) and nano-silica (NS). Investigations were [...]
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Effect of Sulfate Attack on Compressive Strength of Foamed Cement Paste under Static Cyclic Loading
Y. Guanbao, X. Yiling, Z. Zhen, S. Honghui

DBMC 2023.

Abstract
Foamed cement paste has been increasingly used as backfill material in roadways and railway embankments due to its advantages of adjustable density and strength. The embankments constructed by foamed cement paste in coastal regions is subjected to both traffic loading and chemical erosion in service life. This paper conducted a series of durability tests to investigate the reduction of static and dynamic strength of foamed cement paste after the specimens were immersed in sodium sulfate solutions.The specimens were prepared with densities of 800 and 900 kg/m3. The influence factors of specimen density, concentration and cation type of sulfate solution on the strength degradation of the specimens were discussed. The results showed that the corrosion resistant coefficient of the specimens was reduced with the increase of immersion time and concentration of sodium sulfate solution. The degradation of the compressive strength under cyclic loading is more serious than that under static loading. The high density specimens perform better durability than low-density specimens, as the specimens with 900 kg/m3 under 28 and 56 days of sulfate attack had smaller reduction in both dynamic and static strengths than the specimens with 800 kg/m3.
Abstract
Foamed cement paste has been increasingly used as backfill material in roadways and railway embankments due to its advantages of adjustable density and strength. The embankments [...]
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Effect of Endogenous Chloride Ion on Corrosion of Rebar in Sea-sand Ultra-high Performance Concrete
H. Lian, H. Wei, C. Zhendong, C. Rong, W. Jiangang, C. Baochun

DBMC 2023.

Abstract
Ultra-high performance concrete (UHPC) is an innovative cement-based composite material characterized by extremely high durability and mechanical properties, which provides a potential possibility of using non-desalted sea-sand as aggregate. However, the long-term steel corrosion behavior in UHPC prepared by simulated sea-sand under different immersion environments remains unclear. In this study, the pore structure of sea-sand UHPC matrix was measured using nitrogen adsorption/desorption method. The corrosion behavior of rebar in sea-sand UHPC with different endogenous chloride ion contents soaking in pure water and NaCl solution was characterized by electrochemical workstation. The experimental results show that the initial UHPC pore structure is refined by incorporation ofsea-sand, and is similar to that of ordinary UHPC at the later hydration. Regardless of the endogenous chloride ion content and immersion environment, the corrosion rate evaluated by corrosion current density (icorr) and polarization resistance (Rp) of reinforcement in UHPC is extremely low. The measurement of EIS shows that UHPC group has higher matrix resistance (Rc) and charge transfer resistance (Rct), while lower electric double layer capacitance (CPEdl) of reinforcement, which indicates that the steel in UHPC made of sea-sand is still in a state ofpassivation. However, the steel bar in comparison specimen OPC soaking in NaCl solution is in the corrosion stage. Furthermore, sea-sand UHPC possesses of excellent ability of anti- pitting corrosion ofreinforcement after 180 days ofimmersion in NaCl solution.
Abstract
Ultra-high performance concrete (UHPC) is an innovative cement-based composite material characterized by extremely high durability and mechanical properties, which provides [...]
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Carbonation of Concrete Cured Under Different Conditions
O. Kolawole A., A. Nafisat M.

DBMC 2023.

Abstract
Concrete is cured under different conditions to preserve the moist state of the concrete matrix for continuous hydration as it is done on most construction sites. In this study, the effect of different curing techniques on the carbonation depth of concrete mix is presented. Concrete matrix of mix ratio 1 :2 :4 with a water-cement ratio of 0.5 was prepared and cast into cubes of sizes 150 mm. After 24 hours, the concrete cubes were removed from moulds and cured using different techniques for 3, 7, 28, 56, and 91 days. Thereafter, the compressive strength of the concrete cubes and carbonation depths were determined for each curing day. The curing techniques investigated were immersion in water (IM), sprinkling (SP), polyethylene membrane (PM), damp sand (DS), indoor (OI), outdoor (OT), and saturated wet covering (SWC). The results indicated that carbonation depth differed with each of the concrete cured in different techniques. It was observed that concrete exposed outside was worst affected by carbonation followed by those cured indoor, while those cured with polythene showed the least carbonation depth. It was concluded that the polythene membrane curing technique was the best curing technique to limit the effect of carbonation of concrete.
Abstract
Concrete is cured under different conditions to preserve the moist state of the concrete matrix for continuous hydration as it is done on most construction sites. In this [...]
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Biomimetic Organic-Inorganic Hybrid Magnesium Oxychloride Cement as Green Adhesive for Biomimetic Organic-Inorganic Hybrid Magnesium Oxychloride Cement as Green Adhesive for Wood Industry
H. Yufei, K. Xiangming

DBMC 2023.

Abstract
Benefiting from the negative carbon footprint of wood, wood composites have been considered as eco-friendly alternative building materials. However, adhesives for bonding wood components are mainly formaldehyde-based resins, which are highly combustible and continuously release volatile hazardous substances during service. Therefore, the development of magnesium oxychloride cement (MOC) as wood adhesive is highly compliant with environmental regulations and green material requirements. Unfortunately, the extensive application of MOC adhesive is hindered by poor water resistance and weak interfacial interaction with wood. Herein, an oyster-inspired organic-inorganic hybrid strategy was proposed to develop MOC with high adhesion strength and excellent water resistance. Specifically, the renewable chitosan (CS) and tartaric acid (TA) were selected as organic reinforcing constituents to construct a dense double chelating network in MOC, which induced the structural regulation at the bonding interface, thus enhancing the cohesion strength and interfacial properties. Thanks to the biomimetic organic-inorganic hybrid structure, the dry and wet shear strength of the MOC-CS-TA reached 3.08 MPa and 1.77 MPa, making increases of 27.27% and 53.91% compared to the control sample, respectively. Meanwhile, the MOC-CS-TA adhesive presented excellent flame-retardant properties compared with urea-formaldehyde resin adhesives and soy protein adhesives. The design path presented here provides workable guidance for the preparation of eco-friendly cementitious materials and green wood composites in further applications.
Abstract
Benefiting from the negative carbon footprint of wood, wood composites have been considered as eco-friendly alternative building materials. However, adhesives for bonding [...]
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Application of Nanomaterials for Enhancing the Performance of Recycled Aggregate Concrete-A Short Review
X. Caihong, Z. Qingxin

DBMC 2023.

Abstract
Incorporation of recycled concrete aggregates (RA) produced from construction and demolition wastes in concrete contributes to the sustainability from two perspectives: reducing environmental pollution and reserving natural resources by reducing the consumption of natural aggregates (NA). However, comparing to NA, RA has lower mechanical properties and higher water absorptivity due to the old mortar attached on RA surface, resulting in weakened interfacial transition zones (ITZs) in the concrete and the consequent reduced durability of concrete when RA was used to replace NA for producing recycled aggregates concrete (RAC). Therefore, extensive research work had been devoted to the enhancement of RAC performance and nanomaterials have demonstrated great potential in this regard. This paper reviews recent progress on the application of various nanomaterials for improving the microstructure as well as nano/mechanical properties of ITZs in RAC, and special attentions were given to the dispersion strategies for nanomaterials which determines the amount of nanomaterials required to achieve reliable improvement in RAC performance and thus the cost of using nanomaterials in RAC.
Abstract
Incorporation of recycled concrete aggregates (RA) produced from construction and demolition wastes in concrete contributes to the sustainability from two perspectives: reducing [...]
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Modification of Recycled Cement with Different Additives
L. Xu, J. Wang

DBMC 2023.

Abstract
The unmodified recycled cement (RC) paste has unfavorable properties (like fast setting, high water demand and low strength) restricting application. This paper intends to rectify these shortcomings and improve RC with different additives. A comprehensive experimental program combining flowability, setting time, isothermal calorimetry and mechanical tests of modified recycled cement (M-RC) paste with different proportions were conducted. The results indicate that adding TEA and pectin could significantly improve the early flowability of RC and delay its setting, but it will have adverse effects on the mechanical properties of RC paste. Adding 0.5% TEA or 0.075% pectin can increase the fluidity by 240% and 293%. For the 0.5% TEA and 0.075% pectin groups, the 3-day compressive strengths were reduced by 44.3% and 49.5%, respectively.
Abstract
The unmodified recycled cement (RC) paste has unfavorable properties (like fast setting, high water demand and low strength) restricting application. This paper intends to [...]
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Influence of Waste Fibers on the Total Porosity of Cementitious Composites
K. Didulica, A. Pranjić, M. Štefančić, B. Mrduljaš, A. Baričević

DBMC 2023.

Abstract
The amount of water is essential to explain the shrinkage process. It is determined by the water-cement ratio, but also by the moisture content. Water in hydrated cement paste occurs in various forms: chemically bound, interlayer, adsorbed, free water and water vapor. During cement hydration, the balance between various forms of water changes. For example, the amount of physically bound water diminishes, and the moisture content changes at similar environmental conditions. Moisture changes occur first in the larger pores and then in the smaller pores. The air pores are larger than the hydration pores (capillary pores, gel pores) and have a greater effect on strength and permeability properties, while the cement hydration pores have a greater effect on shrinkage. At early ages, when composite properties are not fully developed, higher shrinkage influences the development and propagation of cracks. These (micro)cracks represent weak points and affect durability. To reduce shrinkage and bridge the cracks, fibers are added to the cementitious composite. Depending on the type and geometry, the fibers can reduce shrinkage and bridge the cracks. To reduce the environmental impact of fiber production, the use of waste fibers in cementitious composites is proposed. The main objective of this study was to investigate the influence of alkali-resistant glass fibers from production waste on the development of the microstructure of cementitious composites, i.e., the influence on the total porosity. The pore content was determined on fresh cementitious composites after mixing, while the total porosity of the material was measured after 28 days using a mercury intrusion porosimeter. Results were complemented by X-ray computed microtomography (micro-CT). The influence of production waste fibers is presented as a function of length and fiber content. In addition to the reference mixture, results were also compared with mixtures containing factory-produced fibers.
Abstract
The amount of water is essential to explain the shrinkage process. It is determined by the water-cement ratio, but also by the moisture content. Water in hydrated cement paste [...]
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Effect of Current Modes on Electrochemical Chloride Extraction Treatments for Concrete
C. Song, C. Jiang, X. Gu, Q. Zhang

DBMC 2023.

Abstract
The current mode plays an important role in the Electrochemical Chloride Extraction (ECE) treatment for concrete. In this study, the experiments were conducted to investigate how the ECE process would be affected by different current modes (continuous and intermittent current modes). The results showed that there were remaining amounts of chloride ions that were hard to be removed by both current modes. Additionally, the porosity under the two current modes showed the same upward trend compared to the initial value, and the chloride diffusion coefficient increased by 1 - 2 times. Also, the chloride-contaminated concrete subjected to the continuous current mode had a higher cumulative chloride extraction content than that subjected to the intermittent mode. The intermittent current mode could not increase the effectiveness of extracting chloride when the current density was not greater than 3 A/m2 and the on-off ratio was not less than 3.2.
Abstract
The current mode plays an important role in the Electrochemical Chloride Extraction (ECE) treatment for concrete. In this study, the experiments were conducted to investigate [...]
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Comparison of Non-calcined and Calcined Red Muds from Different Sources as Potential Supplementary Cementitious Material
S. Chen, A. Ghani Razaqpur

DBMC 2023.

Abstract
Red mud (RM) is a hazardous by-product of alumina refining processes. Due to its high alkalinity, large specific surface area, and complex and variable composition, RM is hard to treat or utilize on a large scale. To date, more than 4 billion tons of RM have been stockpiled globally and is still growing by more than 120 million tons annually. Many investigations have focused on the largescale utilization of RM as a construction material, either in its virgin form or after heat treatment. However, the huge differences among the chemical/mineralogical compositions of RMs due to differences among bauxite ores from different sources and/or different refining processes, it is difficult to prescribe a unique process for activating RM cementitious/pozzolanic properties. The present study aims to identify the key chemical and process-dependent factors that influence the cementitious/pozzolanic properties of RM. Two types of RM from different sources are investigated to determine the effects of the chemical/mineralogical composition, the alumina refining process, and calcination on the mineralogical phases and compressive strength of mortar cubes made with ordinary Portland cement (OPC)- RM blended cement. Mortar made with 15 wt.% OPC replaced by one type of virgin RM produced by the Bayer’s process was found to have better strength than a control mortar made with 15% OPC replaced by sand, which indicates that this RM had cementitious/pozzolanic property without requiring heat treatment. On the other hand, the RM produced by the bauxite calcination method needed heat treatment to improve its pozzolanicity, but, despite the improvement, mortar made with its optimally treated form had lower 91-day compressive strength than the companion control mortar made with extra sand as RM replacement. The compressive strength of mortars made with calcined RM was not only affected by the phase changes of the virgin RM properties brought about by calcination but also by changes to its physical.
Abstract
Red mud (RM) is a hazardous by-product of alumina refining processes. Due to its high alkalinity, large specific surface area, and complex and variable composition, RM is [...]
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Rebar-matrix Interface in Extrusion Molded Cementitious Filaments
R. Yang, Q. Zeng, Z. Wang

DBMC 2023.

Abstract
Extrusion molding enables automatic construction through the pattern of material addition. The unique molding would result in several features that are different from those in conventional framework molding, such as weak interlayer bonding and a laminar structure with high anisotropy. To strengthen the interlayer bonding, reinforcement is often implanted to penetrate through the extrusion molded filaments (EMF). However, different from the pre-implantation of reinforcement before concrete casting, the post-implantation of reinforcement in EMF may trigger the problems concerning the interface bonding between reinforcement and material matrix. In this work, saddle stitches, a type of Ushape rebar or fiber, are taken as an example to demonstrate the effect of the post-implantation of reinforcement on the interfacial structure between the rebar and EMF matrix. X-ray computed tomography (XCT) is employed to non-destructively probe the post-implanted saddle stitches as well as the surrounded EMF materials. Regions of interest (ROI) are set on the rebar-matrix interfaces to elaborately analyze the material or defect distributions around the saddle stitches. Results demonstrate that insufficient material filling is observed at the outboard of the U-shape rebar, while material pressing is shown at the inboard. Large defects unevenly form in the rebar-matrix interface. Mechanisms of the observations may be ascribed to the low flowability of EMF materials that can hardly migrate to the rebar-matrix interfacial gaps spontaneously. The findings would deepen the understandings in rebar-matrix interfacial structure of EMF with post-implantation of reinforcement.
Abstract
Extrusion molding enables automatic construction through the pattern of material addition. The unique molding would result in several features that are different from those [...]
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Effectiveness of Paraffin-based Curing Compound for Mitigation of the Plastic Shrinkage and Related Cracking of the 3D-printed Concrete Elements
S. Markin, V. Mechtcherine

DBMC 2023.

Abstract
3D-printed concrete elements are highly vulnerable to early-age shrinkage and cracking compared to conventionally cast concrete elements. Material compositions of printable concretes and complete renunciation of shuttering are responsible for accelerated capillary pressure build-up, leading to volumetric constructions of the 3D-printed layers at a very early age after extrusion and enhanced shrinkage at a later age. Shrinkage-induced cracks can severely impair the durability and appearance of 3D-printed concrete structures. The study at hand analyses the efficacy of the paraffin-based curing agent for reducing the shrinkage and cracking of 3D-printed elements and structures. Development of the temperature and capillary pressure, as well as shrinkage strains, were reported for the cured and uncured specimens. The study results show that applying paraffin-based curing agents can considerably reduce shrinkage-indued deformations of the 3D-printed elements produced even under extreme environmental conditions.
Abstract
3D-printed concrete elements are highly vulnerable to early-age shrinkage and cracking compared to conventionally cast concrete elements. Material compositions of printable [...]
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Effect of Delayed Addition of TEA on the Performance of Cement with Different Sulfate Carriers
Z. Lu, X. Peng, Z. Sun, D. Stephan

DBMC 2023.

Abstract
Concrete 3D printing is one promising technique used for future construction. However, a bottleneck limiting this technology's rapid development and practical application is the conflicting requirements for concrete properties before and after printing. Hence, the application of the accelerator and a deep understating of its working mechanism is becoming more and more important. As one commonly used accelerator, triethanolamine (TEA) has the advantage of low dosage and high efficiency to reach a fast setting. However, it is still unclear how the delayed addition of TEA affects the performance of cementitious materials. Besides, it is found that the different types and combinations of sulfate carriers can significantly affect the performance of TEA on cement hydration. However, the combined effect of different sulfate carriers and different addition times of TEA on the hydration process of cement paste is also unclear. The effect of different TEA addition times on the hydration and setting performance of cement pastes containing different types and combinations of sulfate carriers were thoroughly investigated in this study. It is found that, depending on the types of sulfate carriers inside, the different addition times of TEA can significantly affect the hydration and setting performance of cement paste. Specifically, to artificial cement (ArC) prepared with hemihydrate (HH), the different TEA addition times do not affect the setting performance of cement paste. To ArC with the two sulfate carriers of anhydrite (AH) and HH, a flash setting was observed when the TEA was added simultaneously. However, a delayed addition of TEA for just 5 min can make the setting performance back to normal. To ArC with only AH, a longer addition time of 15 min is needed to eliminate the flash setting behavior. This phenomenon could be originated from the competed interaction of sulfate ions released from sulfate carriers and TEA with the aluminate phase contained in the clinker.
Abstract
Concrete 3D printing is one promising technique used for future construction. However, a bottleneck limiting this technology's rapid development and practical application [...]
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Adapting Construction and Demolition Waste to Circular Building Materials and Evaluation of Life Cycle Environmental Impacts
A. Kul, E. Ozcelikci, B. Furkan Ozel, G. Yildirim, A. Ashour

DBMC 2023.

Abstract
Upcycling of construction and demolition wastes (CDWs) into value-added building materials that can be used for rapid construction and housing in developing countries and disasterprone areas is important and offers a fast, cost-effective, and eco-friendly solution. The objective of this study is to investigate the feasibility of using different-size recycled concrete aggregates (RCAs) in geopolymers made entirely from CDW-based masonry components including hollow brick (HB), red clay brick (RCB), and roof tile (RT) as precursors. To improve the strength development, thermal curing was applied to the developed geopolymer mortars. Compressive strength test was used for mechanical characterization. To assess the environmental impact of geopolymer mortars, a cradle-to-gate life cycle assessment (LCA) was carried out. Findings revealed that RT-based geopolymer mortars were with the highest compressive strength level reaching 66.2 MPa based on different mixture and curing parameters. Compressive strength increased with the reduction in the maximum RCA size. According to LCA analysis, CDW-based geopolymer mortars resulted in similar strength but significant reduction in CO2 emissions (up to 60%) and are with comparable energy consumption to the Portland cement-based mortars.
Abstract
Upcycling of construction and demolition wastes (CDWs) into value-added building materials that can be used for rapid construction and housing in developing countries and [...]
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A Conceptual Model for Assessing Circularity Potential of Building Materials at the Product Manufacturing Stage
N. Tharaka Dharmasiri Pathberiyage, E. Delzendeh, F. Cheung, M. Mateo Garcia

DBMC 2023.

Abstract
The construction industry presently accounts for 30% of natural resource extraction and 25% of solid waste generation. The prevailing economy is “Linear” which is summarised as take-makedispose. On the contrary, the “circular economy” model is a systematic model to restore, regenerate and expand the lifecycle of materials. Most of the existing circularity assessment methods are focused on the end-of-life wastage of building materials while neglecting resource consumption and wastage at the product manufacturing stage. Further, these methods only consider direct material flows for assessing the circularity potential of building materials and overlook the indirect material flows associated with product manufacturing. There is a need to develop metrics to assess the circularity performance of building materials more holistically. Therefore, this study proposes a conceptual model to assess the circularity potential of building materials by analysing both direct and indirect material flow processes of the product manufacturing stage including raw material extraction, transportation, and manufacturing. The method used to design the conceptual model includes a comprehensive literature review in two stages. First, the existing circular assessment methods are reviewed to identify the methods used for assessing the circularity potential of building materials. Secondly, the circularity options are explored to develop the circularity metrics. According to the findings of this study, in the absence of a comprehensive method to assess the circularity potential of building materials, the life cycle assessment and material flow analysis are the most prominent circularity assessment methods used. Furthermore, circularity options such as industrial waste (by-products), biodegradability, biofuels, renewable energy, reusability, recoverability, recyclability and product life span are identified as the circularity metrics for building materials at the product manufacturing stage.
Abstract
The construction industry presently accounts for 30% of natural resource extraction and 25% of solid waste generation. The prevailing economy is “Linear” which [...]
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State-of-Art of Construction 4.0: An Academia Vs Industry Comparative Study
W. Ahmad, S. Azhar

DBMC 2023.

Abstract
The manufacturing industry is experiencing the 4th Industrial Revolution, also known as Industry 4.0. It encapsulates cyber-physical systems (i.e., combining sensing, computation, control and networking into physical objects and infrastructure) integrated towards digitalization and automation of the manufacturing sector. The construction industry has also benefited from these technologies, which go by Construction 4.0. Despite the construction industry often being blamed for its reluctance to implement emerging technologies and non-traditional management methods, recent research attempted to integrate Industry 4.0 emerging technologies to keep up with the manufacturing sector. This shows that academia and industry need each other’s hand-in-hand support in order to implement these technological advances. This study investigates the status of Construction 4.0 technologies adoption in academia and industry in the United States of America (USA) and measures the level of collaboration. Relevant data is collected via web-based questionnaire surveys that are distributed to academia and industry professionals within the USA to inquire about the status of construction 4.0 technologies and their adoption rate. The collected data are analyzed and important findings are reported in this paper. The results show that around 61% of the professionals from academia and 33% from industry are fully or somehow familiar with the term – ‘Construction 4.0’. There has been significant adoption of BIM, laser scanners, and drones in each sector. The rest of the technologies show potential in upcoming years, and academia and industry have methods in place of updating the workforce on new technologies. However, a lack of collaboration has been observed as 50% of the respondents reported no ongoing or past research projects between academia and industry in this domain. It is hoped that the findings of this research will help both academia and industry to join forces to modernize the construction industry.
Abstract
The manufacturing industry is experiencing the 4th Industrial Revolution, also known as Industry 4.0. It encapsulates cyber-physical systems (i.e., combining sensing, computation, [...]
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Reality Capture (RC) Technology for Drywall Installation: A Scan-toPrefab Approach
S. Alathamneh, J. Liu, S. Azhar, R. Burt

DBMC 2023.

Abstract
Drywall, also known as gypsum board, sheetrock, or plasterboard, is a widely used building sheathing material in the US and Canada to create interior walls and ceilings. Typically, the design and construction documents of a project exclude detailed information about the layout of drywall sheets on interior surfaces. Such information is left to the drywall installation crews to determine solely based on their experience. This inconsistent approach often results in substantial rework and waste of material in the field. The construction industry has seen a significant increase in the adoption of Reality Capture (RC) technology in recent years, with the goal of improving the quality and productivity of various construction activities. This research aims to investigate the implementation of RC technology, explicitly Terrestrial Laser Scanning (TLS) and Structure from Motion (SfM, also referred to as photogrammetry), in drywall installation. The research team has developed a framework that utilizes RC tools to capture the as-built information of the framing members of interior walls and penetrations of the MEP systems and uses these RC data to develop prefabricating shop drawings in a Building Information Modeling (BIM) platform for drywall cutting and installation. This framework has been tested and studied on active construction project sites. The preliminary findings indicate that this framework has the potential to lead to a more precise and efficient drywall installation process. This paper also proposes a process model for the execution of the proposed framework for improving drywall installation.
Abstract
Drywall, also known as gypsum board, sheetrock, or plasterboard, is a widely used building sheathing material in the US and Canada to create interior walls and ceilings. Typically, [...]
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Lateral Behavior of Modular Steel Buildings with Diaphragm Connections
X. He, Y. Wei

DBMC 2023.

Abstract
Modular steel buildings are increasingly popular due to their high level of industrialization. Corner-supported modular steel buildings are typically connected by inter-module connections at the corners of each module without continuous diaphragm slab. Therefore, rigid diaphragm assumption could not be adopted when designing modular steel buildings as in-plane deformation of the slab level is significant. To address this issue, the present study introduces diaphragm connections along the edges of modules at the floor slab levels. Then the lateral behavior of modular steel buildings with and without diaphragm connections is evaluated, as well as when a rigid diaphragm is assumed in the structures. The effect of diaphragm connection on lateral behavior of modular steel building under different parameters is discussed, including modular aspect ratio, number of modules in one storey, bracing system, and number of storeys. It is concluded that using diaphragm connections could improve the lateral behavior of modular steel buildings and simplify the design process.
Abstract
Modular steel buildings are increasingly popular due to their high level of industrialization. Corner-supported modular steel buildings are typically connected by inter-module [...]
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Investigation of the Initial Quality of Robotic Tile Installation Based on Coupled Eulerian-Lagrangian Approach
K. Wu, Y. Zhang, X. Kong, S. Zhang

DBMC 2023.

Abstract
In this study, the initial quality of robotic tile installation under various construction parameters and material properties of adhesive were investigated based on the fluid–structure coupling construction models for the first time. First, the models of adhesive application and tile leveling were developed based on the coupled Eulerian–Lagrangian approach. Then, on the basis of these models, various patterns of adhesive application, types of tile leveling loads, numbers of adhesive strips and yield stresses of adhesive were simulated and their influence laws on the initial quality of robotic tile installation were analyzed. Finally, the influence mechanisms of these parameters on the installation quality were revealed in terms of the spacing between adhesive strips, tile rebounding, contact areas and defect distribution. Results showed that the adhesive with horizontal application possessed smaller plastic deformation, kept stable shape of strips and distributed at equal spacing, compared with the one with vertical application. In contrast to a single compression load, its couplings with vibration loads were beneficial to the reduction of tile rebounding. Among the coupling loads, the coupling of shear vibration with compression considerably increased the tile–adhesive contact area until no interfacial defect appeared. The increase of the number of adhesive strips exerts few effects on the installation quality, including slight increases of contact areas as well as diminished interfacial defects. In the case of relatively low and high yield stresses of adhesive, the shear vibration effects were respectively large and small which decrease the installation quality.
Abstract
In this study, the initial quality of robotic tile installation under various construction parameters and material properties of adhesive were investigated based on the fluid–structure [...]
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Intelligent Construction via Digital Twin Approach
M. Lauria, M. Azzalin

DBMC 2023.

Abstract
The paper presents the results of an ongoing research activity dealing with Digital Twin (DT) approaches for Intelligent Construction, optimizing Operation and Maintenance of buildings and urban areas. DT is an essential technological node of Industry 5.0, which leads to the growth of a Collaborative Industry based on the cooperation between machines and human beings to give added value to processes that meet the needs of users. DT realizes the synchronization between two realities: physical objects in real space, virtual objects in virtual space, remaining connected through the mutual exchange of data throughout the entire life cycle of the object. The construction sector is also adopting the new DT perspective to enforce innovative, responsible, and sustainable governance of the life cycle of buildings improving their durability and reducing environmental impacts. Due to IoT, AI, and virtualization, DT approaches permit prediction of future performance in-use, prevent anomalies, downtime, and inefficiencies, to experiment improvements or changes without having to test them on the construction itself or on special mock-ups. The research assumes the aforesaid considerations and states as its principal operational and experimental assets as-built virtual models in OpenBIM connected with Geographic Information Systems and an IoT infrastructure. They realize intelligent constructions integrated with an analytical data communication network for control and performance simulations. Through the study cases analyzed, the paper also introduces arguments for a critical literature review on current statements and future challenges of the DT approach for Intelligent Construction.
Abstract
The paper presents the results of an ongoing research activity dealing with Digital Twin (DT) approaches for Intelligent Construction, optimizing Operation and Maintenance [...]
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Influence of Temperature Increase on the Degradation Evolution of Rendered Façades
J. Barrelas, A. Silva, J. de Brito, A. Tadeu

DBMC 2023.

Abstract
Climate change could alter the natural degradation pattern of buildings and their components. Façade claddings are directly exposed to the action of environmental agents, thus being particularly vulnerable to climate change impacts. Determining the expected degradation of the façades’ external layer, according to climate parameters’ projections, could be useful in the context of maintenance planning and adaptation to climate change. The present study intends to deepen the knowledge about the influence of temperature on the degradation evolution of rendered façades, considering the analysis of possible correlations between variables, based on observed and recorded climate data. It covers the degradation evolution of a sample of 26 rendered façades located in Lisbon, Portugal, based on the mean triennial degradation rate (∆Sw,mt) for periods of three years between 1990 and 2020. The severity of degradation index (Sw) of each façade, assessed through visual inspections in two moments in time, is used to model the individual degradation of the respective case study, necessary to calculate the sample’s ∆Sw,mt of to each triennium. The correlation between the dependent variable ∆Sw,mt and the independent variable ‘maximum temperature’ is significant, with a Pearson correlation coefficient of approximately -0.89. The negative trend shows that the degradation of the sample tends to decelerate with the increase of maximum temperature. Therefore, the temperature warming projected for the end of the century could contribute to lessen the rate of rendered façades’ degradation in the future, in Portugal or in analogous areas of the Mediterranean. The present study is part of a methodology that is being developed to quantify the impact of changes in climate parameters on the future degradation of rendered façades. Further research is necessary regarding the degradation projections, based on the climate change signal for maximum temperatures.
Abstract
Climate change could alter the natural degradation pattern of buildings and their components. Façade claddings are directly exposed to the action of environmental agents, [...]
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Impact of High-resolution Regional Climate Conditions on the Moisture Performance of Wood-frame Building Envelopes
C. Aggarwal, L. Wang, M. Junginger, M. Defo, A. Gaur, H. Ge, M. Lacasse

DBMC 2023.

Abstract
Climate data is one of the most important inputs for hygrothermal simulations and significantly influences the simulation results that are used for moisture performance assessment of building envelopes. Conventionally, climate data from representative weather stations are used for hygrothermal simulations to assess the moisture performance of the buildings. Recently, the Construction Research Centre of the National Research Council Canada generated historical and future climate data for 564 locations across Canada. In this paper, the climate data of four urban locations within Vancouver (a humid and warm coastal city in Canada) were selected for hygrothermal simulations. These include an open area at the airport, a city center, an area surrounded by plants, and an area surrounded by a water body. The 31-year-long simulations were performed for a typical woodframe wall assembly complying with moisture protection designs as provided in the National Building Code Canada (NBCC 2020) but rain penetration was assumed considering the deficiency of exterior cladding. The differences in its hygrothermal response across the four locations were analyzed. It was found that some climate parameters are significantly different among the selected locations, although the values for moisture indices given in the NBCC 2020 for these locations are all similar. The results show that high values of WDR are the dominant factor that drives the moisture performance but there is no indication that the design of the assembly could be different among the tested locations.
Abstract
Climate data is one of the most important inputs for hygrothermal simulations and significantly influences the simulation results that are used for moisture performance assessment [...]
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Hygrothermal Performance of External Wall Systems Under Current Climatic Conditions and Future Climate Projections of Turkey
C. Baş, A. Türkeri, M. Lacasse

DBMC 2023.

Abstract
External wall failures caused by rainwater ingress are very common in Turkey. External wall systems that fail to meet the expected watertightness performance may cause premature deterioration of building components, create health hazards for users, and lead to a financial burden for building owners and in respect to the premature deterioration of public buildings, this also has repercussions on the national economy. In addition to the current climatic conditions, thermal and moisture loads that effect the buildings are expected to increase in the future due to climate change. In regards to climate change mitigation strategies, as have been emphasized for the building sector in Turkey, the national government is promoting the use of thermal insulation. However, given that the thermal performance of the most commonly used thermal insulation materials in Turkey are affected by moisture, it is important to evaluate the hygrothermal performance of external wall systems to help ensure the effectiveness and longevity of any proposed measures to mitigate the effects of climate change on building performance. In this paper, the state of the art is presented in respect to investigations of the hygrothermal performance of external wall systems. The research is analyzed based on climatic conditions to which the wall is exposed, the type of external wall assembly investigated, and the method of investigation described in the studies reviewed. The results indicate that the hygrothermal performance of external walls has been extensively investigated; however, there is relatively little research focusing on the hygrothermal performance of external walls subjected to the current climatic conditions of Turkey. In those studies that focused on evaluating the hygrothermal performance of external wall systems under future climate projections, these have been conducted for the cold climate regions of Canada, USA, Norway, and Finland. The hygrothermal performance of external walls under future climate projections for any region of Turkey has not yet been explored.
Abstract
External wall failures caused by rainwater ingress are very common in Turkey. External wall systems that fail to meet the expected watertightness performance may cause premature [...]
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Evaluation of Defects Incidence and Severity on Building Façade: A Case Study
H. Yasemin Cakir, S. Emanet, Z. Melis Oguz

DBMC 2023.

Abstract
20th century buildings are referred to as modern heritage and suggested to be conserved them because they reflect the particular characteristics of the period. To conserve and sustain modern buildings against agents of degradation, such as the inherent quality characteristics, environmental agents, and operational conditions, an important consideration is the observation, from inspection, and documentation of building defects as may reflect the current condition state of the building. In the scope of the study, façade defects of one of the modern period buildings located in the Fatih district of Istanbul/Turkey – the Istanbul Esnaf Hospital was inspected and analyzed. This building was constructed between 1955-1963 with T-shaped plan which consists of eight façades, for which defects, located on six of the building’s façades, were evaluated. The aim of the study is the evaluation of defects in relation to: the orientation of the façade; the location defects on the façade; the façade material, that consisted of a rendered and painted façade, incorporating a mosaic of ceramics, and; the perceived causes of defects. The study consists of three stages (i) data collection, (ii) analysis of defects, and (iii) comparative evaluation of defects. In the first stage, environmental, architectural, and material data are presented. After which, defects on the building façade were detected through a field inspection and were systematically classified. In the final stage, the findings from comparative evaluations of defects and their relation to the orientation of the façade, location on the façade, material, and causes are given. The analysis shows that the incidence of defects is primarily related to design decisions, i.e., the architectural features of the building. Dirt/stain and cracking are two of the most observed defects. Stain/dirt defects are mostly observed under windowsills and recessed areas due to architectural features typical of this modern period. Whereas it was observed that cracks were generally locate around openings and balconies. Material loss and detachment were generally related to impact from vehicles and were concentrated on two of the façades having high usage. On the other hand, biological growth, and efflorescence were principally caused by outdoor environmental conditions.
Abstract
20th century buildings are referred to as modern heritage and suggested to be conserved them because they reflect the particular characteristics of the period. To conserve [...]
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A Comparison of Nature-based Solutions and Related Policies for UrbanEnvironment in China and Canada
Z. Xiao, H. Ge, M. Lacasse

DBMC 2023.

Abstract
Nature-based solutions (NBS) are considered and implemented in many places around the world as a means to mitigate the impact of climate change on the urban environment. NBS can provide useful approaches to mitigate the urban heat island effect, reduce energy consumption of buildings, sequestrate carbon from the atmosphere, as well as improve comfort to pedestrians in the urban environment. However, the implementation of NBS usually requires extra resources, i.e., valuable land within the urban fabric, additional funds for the design and construction of buildings that incorporate NBS, and additional operational costs for maintaining relevant systems, which may conflict with individual building owner’s interests, but nonetheless, be beneficial for the public at large. Under these circumstances, relevant policies should be established to set minimum performance requirements and incentives be introduced to encourage the implementation of relevant practices. China and Canada have set a target of achieving carbon neutral, by 2060 and 2050, respectively. Implementing such policies is critical for realizing the contributions of NBS in the building sector and helping achieve carbon neutrality in urban areas. For the study described in this paper, polices related to the implementation of NBS as issued by selected cities in China and Canada are reviewed. Scopes and limitations of policies from these two countries are summarized and compared. Suggestions and requirements provided in the policies are discussed in conjunction with the findings and conclusions from scientific articles related to the NBS.
Abstract
Nature-based solutions (NBS) are considered and implemented in many places around the world as a means to mitigate the impact of climate change on the urban environment. NBS [...]
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How Environmental Circumstances Influence Water Repellent Treatment Efficiency – A Case Study of Bentheim Sandstone
X. Chen, T. De Kock, V. Cnudde, N. Van Den Bossche

DBMC 2023.

Abstract
Water repellents are widely applied directly to the outer surfaces of existing buildings to increase the hydrophobicity and durability of historic facades. Nevertheless, there is little control over the initial moisture content inside masonry and boundary conditions in practice. The fluctuating temperature and moisture content of a wall are inevitable when applying the treatment under natural climatic conditions, therefore the efficiency under realistic application approaches may not be as optimal as in the lab. This research aims to understand how application circumstances affect the hydrophobic efficiency of a siloxane-based water-repellent solvent on sandstone. Samples with different moisture content were treated and cured under different temperature to simulate various field climate conditions in practical applications. The experiments indicate that application temperature and relative humidity have little effect on water-repellent efficiency. The water-repellent product is also effective on saturated walls.
Abstract
Water repellents are widely applied directly to the outer surfaces of existing buildings to increase the hydrophobicity and durability of historic facades. Nevertheless, there [...]
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Holism vs. Sustainability in Construction
T. Szkuta

DBMC 2023.

Abstract
Introduction, motivation: almost 40 years of observation, work and cooperation with investors, designers, contractors, manufacturers, distributors, authorities directly in the construction, rescue of monuments, problem solving, design, implementation, maintenance of facilities is a field of research. I have been there to see how and why construction facilities are implemented, used and protected. The title holism is a good method for analyzing problems but also a tool for predicting the necessary characteristics of what we want to create. Holism is a way of thinking about a problem. Where it is applied it gives good results, especially in the long term. It allows one to see the consequences of the flow of time more easily than reductionism. The study of the causes of a problem is broader which allows us to better diagnose and solve it. It makes you always analyze the effects on the whole object and its environment. It places each problem in the context of nearer, farther, sometimes very far and the passage of time. An important element is the analysis of human behavior during the creation and life of the object. Most of the ways to research and determine the condition of objects are obviously known and used. The problem is to determine them (almost) all and the details. Understanding Aristotle's "The more you know, the more you realize you don't know." is crucial here. The point is to explore and come to a conclusion without "closing the door" to more sometimes diametrically opposed knowledge as you go along. Holism in construction can be formulated, describing principles so as to facilitate broader analysis. Such an approach is desirable, which will give the opportunity to benefit from the results to people with different levels of competence, that is, the majority. The purpose of the paper is to try to systematize the approach and show, with examples, why it is worth using. Method: shown in the table are the elements of the research method used in the appraiser's practice. Some areas and elements should be analyzed for the recognition and determination of conditions, impacts and behaviors of construction objects are described. It was determined how to situate the problem in the broadest possible context, with particular attention to typical human behavior. As it turns out, this context is underestimated here. Due to the small volume of the text, examples were limited to the analysis of two relevant elements: lime mortar brick masonry and monolithic reinforced concrete. Objects from the appraiser's practice were selected. For masonry, a school building from the early 20th century and a farmhouse from the mid-19th century. For reinforced concrete, the school swimming pool erected in 1968 and the building of the printing house from 1972, both in emergency condition. Results: The time caesura is important for the results of the conducted research. The indicated errors in the selection of repair methods and materials are due to simplistic methods of analyzing problems. Overlooking the longevity of existence under different conditions and the most important influence of human behavior at each stage of the establishment, use and existence of building structures prove to be crucial.
Abstract
Introduction, motivation: almost 40 years of observation, work and cooperation with investors, designers, contractors, manufacturers, distributors, authorities directly in [...]
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Corrosion Initiation Period for Stainless Steel Reinforcement in Concrete Structures
L. Abreu Araujo, I. Helices Arcila, N. Rebolledo Ramos, J. E. Torres Martín, S. Chinchón-Payá, J. Sánchez Montero, B. B. Raggiotti, V. Matres

DBMC 2023.

Abstract
The designed service life of reinforced concrete structure is often shortened when disposed in aggressive environments. In certain situations, stainless steel reinforcement may be an appropriate replacement to attain a higher level of durability. This paper presents the findings of an experimental study conducted to determine the critical chloride threshold for two types of stainless steel reinforcement (UNS S40977 and UNS S32001). For each steel grade, a prediction model for the corrosion initiation period was obtained, applying the electrochemical test data in a Monte Carlo analysis. Results show that if the initiation period is taken as the corresponding for a 7% corrosion probability, that will occur at 6.5 years of age for carbon steel and over 150 years for UNS S32001 stainless steel.
Abstract
The designed service life of reinforced concrete structure is often shortened when disposed in aggressive environments. In certain situations, stainless steel reinforcement [...]
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Assessing Different Insulation Strategies for Historic Wooden Facades Based on Modeled Mold Growth Risk
M. Zhao, H. M. Künzel

DBMC 2023.

Abstract
Wood makes up a considerable proportion of applied construction materials in Chinese historic building envelopes. With increasing awareness of preserving historic heritage by promoting their further use and occupation, it becomes necessary to improve the current poor indoor thermal environment in abundantly existing historic buildings in southern China. One common approach for improvement is to install insulation materials on historic building envelopes, which can additionally improve their sustainability by reducing buildings’ energy demand for heating and cooling. However, this measure of deep retrofits requires cautious design regarding the hygrothermal performance of insulated wooden facades, since an improper construction way would lead to mold growth in wooden materials, causing problems of durability and indoor hygiene. Therefore, this study investigates the mold growth risk of different insulation systems for historic wooden facades in the Chinese HotSummer-Cold-Winter zone based on a parameter study. The considered parameters are internal and external insulation systems, vapor-open (mineral wool) and vapor-tight (XPS) insulation materials, a U-value of 0.8 W/(m²K) as well as a lower U-value of 0.24 W/(m²K) for the insulated walls, different capabilities and positions of an additional vapor control layer, as well as different cooling/dehumidification conditions in the warm period of a year. The hygrothermal performance of insulated wooden facades is simulated with WUFI®Plus software, while the mold growth risk is assessed with mold index values of the Viitanen mold model. The results of this paper will provide a quantitative evaluation of different insulation strategies for historic buildings in southern China regarding the mold growth risk in wooden materials, which is of essential importance for the durability of construction materials. This study can also give instructions for deeply retrofitting wooden historic buildings in China.
Abstract
Wood makes up a considerable proportion of applied construction materials in Chinese historic building envelopes. With increasing awareness of preserving historic heritage [...]
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A Dose-response Approach for Predicting Frost Damage with Hygrothermal Simulations
K. Janssens, C. Feng, V. Marincioni, N. Van Den Bossche

DBMC 2023.

Abstract
Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the materials, which may not always be an option due to heritage values, it is highly important to quantify the risk of frost damage in advance. Hygrothermal simulations have proven to be a valuable tool to assess the risk of deterioration of building facades. The performance criterion method generally applied today quantifies the number of critical freeze-thaw cycles (FTCcrit) as described by Mensinga et al (2010). This method is based on frost resistance tests that adopt high moisture contents and extremely low frost temperatures. However, building facades often experience milder frost temperatures and lower moisture contents rather than these extreme conditions. A journal article published by Feng et al. (2019) investigated the relationship of frost damage with temperature and moisture content, which enables a dose-response approach that goes beyond the existing threshold level criteria. The experimental study tested freezing temperatures from -2°C to -20°C and moisture saturation degrees from 0.1 to 1.0. This paper studies freeze-thaw risk using this advanced approach, and investigates whether the dose-response approach can lead to a clarification at what number of FTCcrit actual deterioration occurs and how this can be predicted by the use of hygrothermal simulations. Thereby, an attempt is made to derive a more representative performance criterion for frost damage.
Abstract
Freeze-thaw degradation is one of the most prominent degradation risks of brick facades. Considering the difficulties of repairing freeze-thaw damage without replacing the [...]
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Why the Quality of Concrete Construction for Infrastructure Contracts Must Not be Undermined by Inappropriate Design Code Assumptions
S. R. Curtis

DBMC 2023.

Abstract
The concept of a draft international project specification (DIPS) has long been under consideration in relevant fib Task Groups, - even before the framework Standard, ISO 22966 (Execution of concrete structures) was published (2009). However, the quality requirements of ISO 22966 were developed from the product quality inspection principles of the Eurocodes and ISO 9001:2000; and the author has explained why these principles cannot be applied directly to contract works. Furthermore, these principles do not demand the necessary level of high-performance concreting and supervision to produce defect-free structures and the 100 plus year service life which Owners expect. The original ISO 9001:1987 was a simple, contractually effective model quality system specification which “aimed primarily at preventing nonconformity,” (the fundamental purpose of quality assurance). Its most powerful element was ‘process control’ (including ‘special processes’), and it demanded that all processes which could adversely affect quality must be addressed by effective documented preventive procedures in the Contractor’s Project Quality Plan (PQP). The Contractor had to document exactly how he would perform each (special) concreting process and then demonstrate that his proposed procedures worked. Since 2000, this powerful combination of mandatory quality planning requirements has been removed from most specifications for concrete works; but this is precisely what needs to be restored if Owners’ and Designers’ durability expectations are to be consistently achieved. The author now proposes an amended draft version of the International Project Specification, - hoping that it will soon be used on a trial basis on selected construction contracts for reinforced and prestressed concrete bridgeworks in China, Australia, United States and Europe.
Abstract
The concept of a draft international project specification (DIPS) has long been under consideration in relevant fib Task Groups, - even before the framework Standard, ISO [...]
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Validation Exercise at European Level on Natural Chloride Diffusion Test and Natural and Accelerated Carbonation Testing
C. Andrade

DBMC 2023.

Abstract
The work summarizes the results of the interlaboratory testing made in the committee CEN/TC51/WG12 on the standardized procedures for carbonation (EN 12390 – 10 and part 12) and chloride diffusion (EN 12390-12). The exercise was made by 13 different laboratories on 8 different concrete compositions with w/c ratios of 0.4, 0.5 and 0.6. The results indicated repeatability of 10-22% for natural carbonation (outdoors protected from rain and controlled chamber respectively), of around 5% for accelerated carbonation (at 4% of CO2 concentration), and 23% in the Apparent diffusion coefficient for natural chloride diffusion and 13% for the chloride surface concentration.
Abstract
The work summarizes the results of the interlaboratory testing made in the committee CEN/TC51/WG12 on the standardized procedures for carbonation (EN 12390 – 10 and part [...]
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Link between Durability Defects and Construction Failures
S. R. Curtis

DBMC 2023.

Abstract
Over thirty years ago enthusiastic and dedicated materials scientists and structural engineers initiated a series of research projects and draft International Standards which has now revolutionised the design approach to durability of concrete structures. Concrete mix design is dominated by the contractual requirement for the concrete supply not to exceed specified limiting values of the nationally favoured durability criteria. The specifying Authorities are striving to ensure that structures achieve their design service life (ideally 100 years+). Concrete research and development is their primary hope. During the 1990s, the concrete construction industry was also working hard to develop better specifications and contract management procedures to address the pressing problems of not only durability but also safety. Central to all the work of the construction industry was the principle that all concreting operations were ‘special processes’ (as universally acknowledged for welding processes), and therefore they had to be documented, trialled, verified and implemented in compliance with the process control requirements of ISO 9001:1987/1994. Procedures had to be prepared, approved and implemented for all processes which were identified as being potentially ‘adverse to quality’ (which included most processes involved in concreting and prestressing operations (including grouting)). The critical question to answer in preparing a procedure is HOW the process will be carried out and verified. However, equally critical questions may be WHEN, WHERE and BY WHOM. The Project Specification must ask these questions in the tender documents and the Owner and/or his Designer must satisfy themselves that all the identified problems have been resolved – both technical and administrative – before relevant design/construction commences. These questions must be answered by all subcontractors, including designers and checkers of falsework structures. Example are given, based on recent fatal bridge collapses largely caused by Owner and Designer failings to control subcontracting of temporary works design and checking.
Abstract
Over thirty years ago enthusiastic and dedicated materials scientists and structural engineers initiated a series of research projects and draft International Standards which [...]
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Electrical Resistivity Measurements on Hardened Concrete Exposed to Various Curing Conditions
S. Gao, R. Douglas Hooton, K. Li, T. Hao, X. Feng

DBMC 2023.

Abstract
Evaluating concrete quality and performance, especially determining the resistance of concrete to fluid and ion ingress, is fundamental to estimating concrete’s durability and predicting the service life of concrete structures. Both bulk and surface electrical resistivity tests have gained increasing interest as rapid and repeatable indicators of concrete’s resistance to fluid ingress. In this study, concrete electrical resistivity was measured at the ages of 56 and 91 days on specimens from five concrete mixtures exposed to different curing environments and storage solutions. Both bulk and surface resistivity of concrete in each curing condition are compared, and the effect of curing methods on electrical resistivity is discussed. The results show that conditioning in a highly-conductive storage solution, such as a simulated pore solution, led to a lower concrete resistivity measurement than when stored in saturated limewater. The effect of mixture compositions on measured resistivity revealed that for the same cementitious materials, the electrical resistivity increased as the w/cm ratio decreased, and a linear correlation between the w/cm ratio and concrete electrical resistivity was obtained.
Abstract
Evaluating concrete quality and performance, especially determining the resistance of concrete to fluid and ion ingress, is fundamental to estimating concrete’s durability [...]
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Application of Service Life Planning to Existing Buildings – Perspectives on Condition Appraisal, Performance and Cost
K. P. Bourke, A. Silva, P. L. Gaspar

DBMC 2023.

Abstract
ISO 15686 on Service Life Planning of Constructed Assets provides guidance which is applicable to both new and existing constructed assets and their parts. However, there has been limited exposition of the applicability of the guidance to existing buildings. This paper provides perspectives on practical application of the principles to condition assessment (survey and appraisal) of the long-term performance of existing buildings, in particular in respect of the building envelope and how maintenance interventions and life cycle costs are predicted or estimated. The authors are currently actively involved through CIB W080 and ISO TC59/SC14 in preparing for the revision of the ISO 15686 standards to take account of experience over the last 20 years, including the development of the factor method and its applicability, and guidance on life cycle costing of existing buildings. The paper will develop key themes from the series of ISO 15686 standards, which are particularly relevant to assessment of existing buildings and other constructed assets.
Abstract
ISO 15686 on Service Life Planning of Constructed Assets provides guidance which is applicable to both new and existing constructed assets and their parts. However, there [...]
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Prediction and Ranking of Moisture Severity of Climate Years Using Supervised Projection to Latent Structures Applied to Tall Wood Buildings
M. Defo, M. Lacasse, T. Moore

DBMC 2023.

Abstract
Hygrothermal simulation tools are commonly used to assess the moisture performance of building envelope components. Owing to the computational costs required to complete simulations over the long-term, one approach to reduce simulation time when undertaking hygrothermal design analysis is to select representative year(s) amongst sets of long-term climate data. To properly select these moisture reference year(s), a method is required to rank or predict the moisture severity of climate years for sets of long-term climate data. Several methods are used in the literature for this purpose, but none seems to be sufficiently accurate. In this study, the supervised projection to latent structures, also known as partial least squares regression, was trained and validated on data obtained from hygrothermal simulations of tall wood building wall assemblies for several cities across Canada. Models developed at the city level, for a given greenhouse gas emission scenario or time period, or encompassing historical and future time periods, showed comparable scores for ranking. In respect to prediction of the moisture severity of climate year sets, models developed at the city level were shown to be more accurate.
Abstract
Hygrothermal simulation tools are commonly used to assess the moisture performance of building envelope components. Owing to the computational costs required to complete simulations [...]
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Opportunity-Based Maintenance of Buildings’ Envelope
C. Ferreira, J. de Brito, A. Silva

DBMC 2023.

Abstract
More than half of the building’s life-cycle costs correspond to maintenance costs. Nevertheless, maintenance actions are, generally, conditioned by subjective criteria and carried out at inopportune times, which implies that one third of the maintenance costs are improperly incurred. Buildings are multi-component systems and, therefore, the adoption of opportunistic maintenance policies allows reducing the maintenance costs and the number of interventions, while maximizing the service life and the efficiency of the resources available. In this study, an opportunistic maintenance plan is proposed for the buildings’ envelope, combining the maintenance needs of four elements: rendered facades; ceramic claddings; window frames; and pitched roofs ceramic claddings. For this purpose, a condition-based maintenance model is used. The maintenance model is based on stochastic degradation models for the individual components of the system. The optimization of these policies will identify the best maintenance schedule and combination of maintenance activities, finding the optimal trade-off between disruption of the buildings’ use, maintenance costs and their service life. The application of these opportunistic maintenance policies in the building envelope elements allows mitigating the degradation of these elements over the buildings’ life cycle and, consequently, increasing the economy, quality, and aesthetic perception of our cities. This methodology will change the way that maintenance plans are defined, and interventions are prioritized.
Abstract
More than half of the building’s life-cycle costs correspond to maintenance costs. Nevertheless, maintenance actions are, generally, conditioned by subjective criteria [...]
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Flexibility and Adaptability: A Review on Assessment Methods and Tools and Their Applicability
G. Cignachi, P. Gaspar, H. Farias

DBMC 2023.

Abstract
In this paper, the existing methods for the assessment of flexibility and adaptability in buildings are reviewed. These methods have been tentatively proposed for a number of building types / uses - notably for residential buildings - and generally propose sets of indicators, variables and weights that combine into a score of flexibility. In spite of the limited practical applicability of these methods so far, they provide a stimulating approach to greater use and incorporation of the concepts and strategies of flexibility and adaptability, aiming at an increased performance of buildings.
Abstract
In this paper, the existing methods for the assessment of flexibility and adaptability in buildings are reviewed. These methods have been tentatively proposed for a number [...]
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Durability and Long-term Performance Assessment in Eco-efficient Concrete Mixtures Towards a More Sustainable Cement Industry - A Critical Review
Z. Xia, C. Londero, S. R.A.Dantas, L. F.M.Sanchez

DBMC 2023.

Abstract
In the current need to fulfill a Net-Zero goal to offset greenhouse gas emissions by 2050, the cement industry deeply needs to renovate its process and products. The amount of concrete, and consequently ordinary Portland cement (OPC) used worldwide, far exceeds other industrial materials, contributing to around 8% of global emissions. A recognized solution would be to partially replace clinker with limestone, an available material in many countries with the potential to improve the particle packing of a concrete mixture. Even though several studies have been carried out on the application of Portland limestone cement (PLC) concrete, there is a need for further investigation regarding durability performance. Problems include alkali-silica reaction (ASR), delayed ettringite formation (DEF), sulphate attack, steel corrosion, and freeze/thawing, whose deteriorating effects tend to be maximized in harsh climate countries such as Canada and should be evaluated when introducing distinct materials into concrete. Therefore, this paper aims to review previous assessment of the durability of PLC concrete mixtures. The use of an advanced mix-design method (particle packing model and mobility parameters - PPM+MPs), will also be discussed on its ability to enhance the durability performance of the mixtures. It is expected that novel guidelines to design more eco-efficient concrete mixtures using PLC can be developed to reduce concrete’s cost and carbon footprint, achieving a more sustainable industry.
Abstract
In the current need to fulfill a Net-Zero goal to offset greenhouse gas emissions by 2050, the cement industry deeply needs to renovate its process and products. The amount [...]
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Changes in Educational Buildings at Very Early Stages of Their Life Cycle
G. Cignachi, P. Gaspar, H. Farias

DBMC 2023.

Abstract
Changes always occur in buildings at any stage of their life cycle. In this paper, particular attention is paid to changes that occur very early on this process, sometimes between bidding and very initial construction stages, in the context of public procurement and building. The research is based on the total building stock of the Federal Institute Sul-rio-grandense, in Brazil, which holds presently 14 campuses and more than 120 buildings. Accumulated experience has demonstrated that the prototypical buildings - educational or administrative - designed to be repeated often undergo alterations. The reasons for such changes are identified, along with their impact on the functionality, service life and future maintenance of such assets.
Abstract
Changes always occur in buildings at any stage of their life cycle. In this paper, particular attention is paid to changes that occur very early on this process, sometimes [...]
- 1
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Analysis of the Repassivation of Corroded Bars in Cementitious Materials Subjected to Realkalisation
G. R. Meira, P. R. R. Ferreira, A. A. Meira

DBMC 2023.

Abstract
The effect of concrete realkalinisation on reinforcement repassivation was evaluated by means of electrochemical measurements considering different previous corrosion degrees of reinforcements and different environmental conditions. Reinforcements obtained from a real concrete structure which were activated due to concrete carbonation were used for this purpose. Five different corrosion degrees were considered. All these reinforcements after being classified, were embedded in fresh mortar specimens and were cured in wet chamber for 7 days. After that, they were sequentially subjected to two different environmental conditions; laboratory environment (65% of relative humidity) and 80 % of relative humidity environment. Along all the testing period, reinforcements were monitored on corrosion potential and instantaneous corrosion current density by linear polarisation measurements. Results show that as the previous corrosion degree increases it becomes harder to reach the repassivation condition for reinforcements. This shows that the effectiveness of concrete realkalisation on reinforcement repassivation depends on the previous corrosion degree of reinforcements. The influence of the relative humidity was not significant under the experimental conditions adopted in this work.
Abstract
The effect of concrete realkalinisation on reinforcement repassivation was evaluated by means of electrochemical measurements considering different previous corrosion degrees [...]
- 1
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Durability Assessment and Maintenance Planning of Concrete Structures in Ningbo-Zhoushan Port Main Channel Sea Link Project
L. Li, K. Li

DBMC 2023.

Abstract
This paper performs the durability assessment and maintenance planning of concrete structures during construction phase in the ongoing Ningbo-Zhoushan Port Main Channel (NZPMC) sea link project with a service life of 100 years. The background of this project is first introduced and the durability design at preliminary study phase is recalled; the chloride-induced corrosion of reinforcement steel was considered as the most critical process that controls the design. Then, the durability model for assessment is established for this durability limit state and the statistical properties of the model parameters are given. From the collected data on the concrete cover thickness and modified chloride diffusion coefficients, the statistical properties of these parameters are updated. With the design options adopted in design phase and the updated parameter properties, taking one non-navigable bridge as an example, the achieved reliability levels and failure probabilities are calculated for structural elements under different exposure conditions by using full probabilistic approach. On the basis of the achieved reliability level of durability, a preliminary maintenance planning is performed for the concrete elements in the concrete structures, and the corresponding recommendations are given.
Abstract
This paper performs the durability assessment and maintenance planning of concrete structures during construction phase in the ongoing Ningbo-Zhoushan Port Main Channel (NZPMC) [...]
- 4
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Damaged Swedish Buildings
P. Wallentén, S. Olof Mundt-Petersen, K. O. Anders Joelsson, M. Kläth

DBMC 2023.

Abstract
Damages with a negative influence on the indoor environment often become linked to high costs. Detailed facts about buildings with damages need to be collected and analyzed in order to be able to reduce the number of damages. This paper presents basic facts, such as design, property ownership and year of construction in buildings where 1105 damages were found. In general, the study gives qualitative indications and cross-comparing to other parameters considering damages and causes of damages needs to be done to obtain better results. Buildings with indoor air ventilated or heated crawlspaces have less damages compare to non- or outdoor ventilated crawl spaces. Damages are more common in buildings with poor exterior insulation in the foundation or a no-drainage and poorly ventilated cladding. In the buildings in the study, schools and local authority owned buildings have a high frequency of damages. A higher number of damages were also found in condominium association owned multi-family houses compared to public tenancy owned multi-family houses.
Abstract
Damages with a negative influence on the indoor environment often become linked to high costs. Detailed facts about buildings with damages need to be collected and analyzed [...]
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Classification Systems for the Built Environment: A Cornerstone for the Long-term Performance Analysis
C. Serrat, V. Royano, V. Gibert, J. Rapinski

DBMC 2023.

Abstract
In the long-term performance analysis of the built environment, classification systems are seen as a key consideration. When classifying residential building objects, characteristics such as accuracy, exhaustivity, and consistency are required. It is noticeable that while organizations around the world are working to develop an internationally agreed standard classifier, the use of national classification systems remains widespread. Therefore, this paper focuses on reviewing the most popular classification systems such as CoClass, Uniclass 2015 and OmniClass®, among others, and discusses their strengths and weaknesses, in order to be useful both to the research and technical communities. Based on this, two main contributions are derived. On the one hand, the paper points out that there is no international consensus to use a common classification system. On the other hand, some recommendations are given and illustrated to meet the challenges of classifying existing buildings, in particular under a functional assessment approach.
Abstract
In the long-term performance analysis of the built environment, classification systems are seen as a key consideration. When classifying residential building objects, characteristics [...]
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Causes of Damages in Swedish Buildings
S. Olof Mundt-Petersen, P. Wallentén, I. J. Edskär, K. O. Anders Joelsson

DBMC 2023.

Abstract
Damages, failures and functional defects in buildings create high cost for the owner and the society. It is important to determinate the causes of damages in order to limit the costs. This paper presents the causes of 1105 different damages from a technical perspective from 265 real damage investigations. In general, the results show that; 1. Rain and snow was the most common moisture source cause damages, 2. The number of damages caused by wet concrete and PVC or linoleum flooring may be overestimated. 3. A significant number of damages were caused in details where different materials connect to each other, 4. A high number of damages were linked to wear and tear and poor maintenance. 5. Causes of damages occurs in all phases of the building process but most of them were deemed to occur in the management and on-site construction phase. 6. Most of the damages were caused by building owner or their facility trustees.
Abstract
Damages, failures and functional defects in buildings create high cost for the owner and the society. It is important to determinate the causes of damages in order to limit [...]
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Assessment of the Impressed Current Cathodic Protection System after 4 Years Operation: Evolution Over Temperature and Time of the Applied Current and Tension on Anodic Zones of the Saint-Cloud Viaduct (France)
J. Ducasse-Lapeyrusse, V. Bouteiller, O. Lesieutre, E. Marie-Victoire, M. Bouichou, G. Damien, V. Martinet, C. Annede-Villeau

DBMC 2023.

Abstract
This paper presents the feedback of the Impressed Current Cathodic Protection (ICCP) system implemented on a road bridge, the Viaduct of Saint-Cloud, constructed in the 1970s in France. After a test trial in 2012, the full-scale ICCP system was energized in 2018. It consisted of 44359 discrete titanium anodes implemented on the lateral segment webs on both sides of the Viaduct, distributed in 212 anodic zones on one side and 153 anodic zones on the other side. The four years monitoring data include the variations of the applied current and tension on anodic zones, their polarization, etc. This paper focus on the global resistance of the circuit for the different anodic zones. The circuit resistance shows first the influence of the temperature. The differences between anodic zones and their evolution over time also bring more information about the environment of the anodes and the reinforcements. The analysis of the response of the circuit reveals the heterogeneity of an actual and large-scale ICCP system and provides important feedback to an appropriate ICCP design for durable cathodic protection.
Abstract
This paper presents the feedback of the Impressed Current Cathodic Protection (ICCP) system implemented on a road bridge, the Viaduct of Saint-Cloud, constructed in the 1970s [...]
- 2
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Analytical and Experimental Service Life Assessment of Ningbo-Zhoushan Port Main Channel Sea Link Project
L. Li, K. Li, R. Torrent

DBMC 2023.

Abstract
The Ningbo-Zhoushan Port Main Channel (NZPMC) sea link is one of the most important projects undertaken by the People's Republic of China. The main factors that determine the service life of these marine structures, exposed to chloride-induced corrosion, are the "penetrability" and thickness of the concrete cover that protects the steel reinforcement. In an initial design phase, these factors are defined by modeling the penetration of chlorides with analytical tools (based on the Duracrete approach). In the construction phase, data are collected from the in-site laboratory for concrete chloride diffusivity, and from non-destructive tests for the concrete cover thickness and air permeability for the prefabricated bridge piers. On the basis of these data, two model-based approaches are used to predict the service life of the bridge. The first model is an analytical one based on the solution of Fick’s 2nd diffusion law, for chloride ingress into concrete using the corrosion initiation as durability limit state.The second model uses the “Exp-Ref” model, using the concrete cover thickness and air permeability as input parameters and calibrated by the EuroCode specifications on structural concretes in marine environments. Both approaches use Monte-Carlo simulations and consider the statistical properties of the input parameters. A comparison of the analytical and experimental predictions is made, showing compatibility with 100 years of service life. The convenience of verifying the analytical predictions with those obtained from site experimental data is discussed.
Abstract
The Ningbo-Zhoushan Port Main Channel (NZPMC) sea link is one of the most important projects undertaken by the People's Republic of China. The main factors that determine [...]
- 2
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An In-situ Method for Assessing the Kinetics of Acid Attack on Iron-richAlkali-activated Materials
Z. Yu, R. Oliveira-Silva, E. De Oliveira, N. Wen, Y. Pontikes, D. Sakellariou

DBMC 2023.

Abstract
In iron-rich alkali-activated materials (AAMs), iron is present in both the ferrous and ferric states. Fe3+ is considered to be present in a silicate network and the dissolution of Fe3+ under acid attack can be taken as an indication of the deterioration of the AAMs framework. Conventional methods for evaluating the acid resistance of AAMs are based on the durability standards for OPC concrete with indicators such as mass change and dimensional change, or by measuring the corroded depth. All of these methods are measured based on solid samples and many samples have to be prepared to obtain different points in a time profile. Here we propose nuclear magnetic resonance (NMR) relaxometry measurements as an in-situ method for the direct determination of dissolution kinetics of Fe3+ ions in an acid solution with high temporal resolution. The leaching kinetics of iron-rich AAMs in (sulfuric) acid can be described by the Real Physical Picture (RPP) kinetic model, which was originally used to describe the gas-solid interaction. The fitting results show that the leaching process is controlled by chemical reactions at the beginning and by diffusion over time.
Abstract
In iron-rich alkali-activated materials (AAMs), iron is present in both the ferrous and ferric states. Fe3+ is considered to be present in a silicate network and the dissolution [...]
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Experimental Study of the Development of Stresses in Prestressing Strandsunder Different Environments
D. Xu, C. Chen, Y. Zhao

DBMC 2023.

Abstract
This paper presents findings from an experimental study on the effects of different environmental factors on post-tensioned prestressed concrete beams. The study included four different environments: outdoor shielded, drying-wetting cycles with tap water, drying-wetting cycles with NaCl solution, and drying-wetting cycles with NaCl solution and energized longitudinal rebars. A vibratingstring anchor cable dynamometer was used to measure the stress variation in prestressing strands. The results indicate that ambient temperature affects the trend of stresses in the prestressing strands. The increasing humidity caused by drying-wetting cycles and increasing salinity caused by NaCl solution led to the expansion of the concrete and increased stresses in the prestressing strands. Additionally, the corrosion of longitudinal rebars caused by the impressed-current accelerated corrosion method results in concrete damage and cracking, and continuously decreases the stresses in the prestressing strands. The study is ongoing, and further observations and reports will be made to evaluate the effects of different environmental factors on stresses in prestressing strands of post-tensioned beams.
Abstract
This paper presents findings from an experimental study on the effects of different environmental factors on post-tensioned prestressed concrete beams. The study included [...]
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Exploring Moisture Performance of Two Distinctive Solid Bricks underCurrent and Future Climate in London
B. Xu, S. Zhang, T. Cambray, V. Marincioni

DBMC 2023.

Abstract
The increasing concerns surrounding climate change have raised apprehension about the heightened frequency and intensity of extreme weather events, globally as well as in the UK. Historic solid brick buildings, due to their construction materials and prolonged exposure to changing climate conditions, are vulnerable to the impacts of climate change, resulting in increased moisture risks that undermine their durability. Understanding the moisture behaviour of solid bricks facing climate change is therefore significant. This study aims to investigate the moisture performance, with a specific focus on moisture content, of two distinct types of bricks: handmade bricks from the 19th century and more recent – early 20th century - bricks, under current and future climate scenarios in London. The results reveal that the more recent bricks can have greater susceptibility to climate changes, providing valuable insights for the implementation of effective moisture control strategies and informed decision-making in the retrofitting of solid brick buildings in the UK.
Abstract
The increasing concerns surrounding climate change have raised apprehension about the heightened frequency and intensity of extreme weather events, globally as well as in [...]
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Freeze-thaw Damage Mechanism and Cracking Behaviour of PerforatedPlateau Concrete Structure
J. Mao, K. Fang, L. Mi, H. Jia

DBMC 2023.

Abstract
The harsh environment and poor quality of building materials used in plateau concrete projects adversely affect the ability of such structures to withstand the damaging impact of freeze-thaw. A fast-freezing test with a single variable control was carried out and the process of microstructural changes in the plateau concrete was traced. The results also showed that the plateau curing environment led to an increase in width and porosity of the interface transition zone (ITZ), and that clay content in building materials significantly impacted the microstructure of paste. The frost resistance of plateau concrete was found to be far lower than that of plain concrete. Perforated concrete structures are common in engineering, and concrete members can easily experience frost cracking in cold regions. This study conducts frost heave tests on perforated concrete, aiming at the problem of the frost heave cracking risk of perforated concrete structures in cold regions. The cracking characteristics of concrete with holes under freeze-thaw cycles are mastered by performing rapid freeze-thaw tests on concrete with holes and observing the cracked section. Finally, hydrophobic filling materials were adopted to alleviate the frost heave stress on concrete.
Abstract
The harsh environment and poor quality of building materials used in plateau concrete projects adversely affect the ability of such structures to withstand the damaging impact [...]
- 1
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Hygrothermal Performance of CLT Subjected to Rain Loads duringConstruction in Belgium
K. Habtie, B. Vanderschelden, X. Jiang, L. De Ligne, J. Van Den Bulcke, N. Van Den Bossche

DBMC 2023.

Abstract
As the use of CLT is increasing, it is important to understand how to deal with moisture during construction. Throughout the construction phase it is often not feasible to shield every component and detail from direct rain impingement. This paper investigates what happens to CLT, and spruce wood in general, when it is exposed to rain events, and how fast it dries out afterwards. Subsequently, the implications of incorporating a wetted component into a finished wall system is also investigated. The moisture behaviour of both plain spruce and CLT samples that are exposed outdoors is investigated using the continuous moisture measurement (CMM) setup at the UGent Woodlab in combination with hygrothermal simulations in Delphin 6. Pieces of solid wood and CLT are mounted on load cells that record the weight every 5 minutes, to study the wetting and drying behavior. Hygrothermal simulations are done in Delphin 6 using a climate file that is made from the recorded weather data. This way, the CMM experiments can be recreated in simulations. The goal here is to understand what is happening in the simulations and to look at what influence different parameters have on the moisture content of the samples. Risks of mould and wood decay are investigated, and recommendations are made concerning practical moisture management and risk mititagion for these types of constructions.
Abstract
As the use of CLT is increasing, it is important to understand how to deal with moisture during construction. Throughout the construction phase it is often not feasible to [...]
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Numerical Simulation on the Pouring Process of Self-compacting Concretein CRTS III Slab Track
H. Zhang, Y. Zhang, K. Wu

DBMC 2023.

Abstract
In this study, a fluid-solid coupling model describing the pouring process of self-compacting concrete (SCC) in CRTS III ballastless slab track in straight section was established based on a coupled Eulerian-Lagrangian method, which realized the simulation of the whole pouring process of SCC. The influence law and mechanism of different construction parameters on the pouring process of SCC were studied theoretically. The effects of height and number of funnels on some key indices including the filling rate of SCC, the vertical and lateral displacements of slab track and the forces of withhold were mainly analyzed. The study was aimed at providing theoretical guidance for the intelligent pouring of SCC and the development of intelligent pouring equipment. Results indicated that the higher funnel and double-hole pouring both reduced the pouring time and improved the construction efficiency, and the latter one demonstrated a significant effect. The maximum vertical displacement of track slab was appeared in the middle of slab edge during single-hole pouring but was found in the vicinity of observation hole during double-hole pouring. The maximum lateral displacement of track slab was appeared near the withhold during the pouring process. A higher funnel led to greater pressure of SCC to track slab, which brought about larger vertical and lateral displacements of slab track and higher forces of withhold. Compared to single-hole pouring, the final floating dis-placement and lateral displacement of slab track and the force of withhold were greater during double-hole pouring
Abstract
In this study, a fluid-solid coupling model describing the pouring process of self-compacting concrete (SCC) in CRTS III ballastless slab track in straight section was established [...]
- 1
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Modeling the Sulfate-induced Damage of Concrete
P. Dangla, Y. Gu, Y. Omikrine-Metalssi, R. Martin

DBMC 2023.

Abstract
The degradation of concrete due to sulfate attack from internal or external sources is a serious problem. The cause of this degradation is the formation and growth of ettringite, which results from the reaction of cement hydrates with sulfate ions in the pore network. This crystal growth leads to a pore pressure that can exceed the concrete’s strength. This paper presents a modeling of concrete’s sulfate-induced stress-strain behavior based on damage poromechanics and two kinetic laws for ettringite growth. Free expansion of cement paste samples exposed to sulfate solutions were measured, and mercury porosimetry tests were conducted at different expansion stages. The pore size distribution was analyzed to locate the dissolution of hydrates and precipitation of ettringite at the pore scale. Results support the theory that ettringite first precipitates in larger capillary pores and spreads to smaller ones. A heat-based dissolution test was performed at different expansion stages, revealing ettringite formed in the pore size range of 4-30 nm. The model was implemented in a finite volume code and applied to four experimental cases from the literature: ESA and DEF in confined and free conditions. The kinetic coefficients were calibrated to fit the observed strains in some experiments and used to blindly test the model in others. Diffusion was neglected due to the small sample size. All simulations showed that the calibrated kinetic parameters had the same order of magnitude, supporting the right physics involved
Abstract
The degradation of concrete due to sulfate attack from internal or external sources is a serious problem. The cause of this degradation is the formation and growth of ettringite, [...]
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MARS – A Multiphysics Framework for the Analysis of Cast and PrintedConcrete
A. Cibelli, R. Wan-Wendner, J. Vorel, D. Pelessone

DBMC 2023.

Abstract
Predicting the time-dependent responses of concrete and concrete structures remains a challenging task in the construction sector. While experimental investigation serves as an essential cornerstone for concrete research, by itself it only offers limited insights into the complex time-dependent behaviour of concrete. The complexity is due to the multiple coupled hygro-thermo-chemo-mechanical processes. In the last two decades MARS, a special purpose computational software developed by ES3, has shown the capability of turning such insights accessible. This paper aims to provide a state-of-theart of the MARS capabilities in concrete modelling, enriched with a discussion of some meaningful examples. The multiphysics framework today available in MARS already allows to simulate a wide range of complex phenomena, featuring the long-term performance of ordinary and advanced cementitious materials.
Abstract
Predicting the time-dependent responses of concrete and concrete structures remains a challenging task in the construction sector. While experimental investigation serves [...]
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Effects of Surface Layer on Moisture Transport in Cementitious Materials:Experimental Evidence and Simulation Results
Z. Zhang, U. Angst

DBMC 2023.

Abstract
Moisture in concrete is the essential factor of many degradation mechanisms to reinforced concrete structures, such as carbonation, chloride ingress, and frost attack. Therefore, it is important to arcuately determine and predict moisture state and moisture distribution inside the material. Most moisture transport models generally view concrete as a homogeneous material, which might be appropriate for the large scale. However, it is commonly found that the properties (chemical and microstructure) of the concrete surface layer are different from the bulk concrete. When considering the moisture exchange with the surrounding environment, this surface layer may unavoidably affect the process of moisture transport. In this study, water absorption tests were performed to investigate moisture transport in uncarbonated cement pastes and mortars. The results show that during the process of sample preparation, the microstructure of the surface layer was altered, leading to anomalous moisture transport, in which the conventional models can not predict the measured mass change. Based on the experimental results, the non-homogeneous simulation domain was created to represent the more realistic microstructure of concrete. The numerical simulation results show a similar trend of the mass change due to moisture transport to the experimental results. Therefore, the nonhomogeneous microstructure of concrete, in particular the different microstructure of the surface layer from the bulk concrete, can be one of the reasons that cause the anomalous moisture transport in cementitious materials. This also emphasizes the importance of sample preparation in the lab, which must avoid creating a surface layer with the different microstructure from the bulk concrete
Abstract
Moisture in concrete is the essential factor of many degradation mechanisms to reinforced concrete structures, such as carbonation, chloride ingress, and frost attack. Therefore, [...]
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Degradation Behavior of GO-ternary Blended Nano-concrete Compositesunder Accelerated Sulfuric Acid Attack
A. Anwar, X. Liu, L. Zhang

DBMC 2023.

Abstract
Biogenic corrosion of concrete in wastewater sewer systems is caused by the in-situ production of sulfuric acid (H2SO4) formed by the bacterial action is considered the principal cause of structural degradation. The intense corrosive environment disintegrates the service lifespan of concrete structures significantly sooner in its advanced state, resulting in structural collapse within 10-20 years and jeopardising its durability. Thus, the degradation of concrete structures in the aggressive acidic environment of sewerage systems remains a global concern for industries and stakeholders, resulting in economic losses of several billion dollars annually. This research experimentally investigates the degradation behavior of developed ternary blended nano-concrete composites reinforced with graphene oxide (GO-TBNCCs) under accelerated H2SO4 exposure (pH 1.0) for 28 days and 90 days. The experimental results revealed that TBNCCs reinforced with GO are more resistant to aggressive acidic attack in contrast to its control composites, hence increasing its acidic resistivity performance with lower degradation depth that may cater to the durability problem of concrete structures in the wastewater sewer systems.
Abstract
Biogenic corrosion of concrete in wastewater sewer systems is caused by the in-situ production of sulfuric acid (H2SO4) formed by the bacterial action is considered the principal [...]
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- 5/5
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An Experimental and Numerical Study of the Effect of Heat and ThermalShock in Precast Concrete Wall System
C. Cremonesi, G. Akyo, O. Oliveira, L. Alves de

DBMC 2023.

Abstract
The aim of the paper is to analyse the performance of a precast concrete wall system under heat and thermal shock (physical phenomena). The understanding of thermal shocks in building systems is a challenge because of the requirements and complexities of the phenomena behaviour through cycles of heating and cooling provided by the environment (sun followed by suddenly rain). The period of duration of the phenomenal during the cycles makes changes in the systems responses in terms of mechanical and physical aspects. The responses of the building system to heat and thermal shock were analysed during the monitoring of the changes in temperature and deformation using sensors in a scalable prototype of a precast concrete wall system. In addition, a numerical simulation based on the finite element method (FEM) in commercial software was conducted to verify and analyse the variables in a digital model of the wall as a complementary study of the effects of heat and thermal shock. The results demonstrated the feasibility to use numerical simulation to analyses the phenomenal of heat and thermal shock on the behaviour of a precast concrete wall system.
Abstract
The aim of the paper is to analyse the performance of a precast concrete wall system under heat and thermal shock (physical phenomena). The understanding of thermal shocks [...]
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Effect of Repeated Loading on the Flexural Load Carrying Capacity ofMarine Concrete Beams Exposed to Chloride Environment
C. Lu, C. Feng, Y. Zheng

DBMC 2023.

Abstract
To investigate the effect of repeated loading on the flexural load carrying capacity of marine concrete beams suffering from chloride attack, a total of 10 marine concrete beams and 27 concrete cubes were designed for flexural performance test and compressive strength test, respectively. Three damage mechanisms, including repeated loading with a stress level of 0.4, chloride salt dry-wet cycles and coupling action of repeated loading history and chloride salt dry-wet cycles, were applied for concrete beams and cubes. Test results show that the effect of repeated loading on the degradation of compressive strength of concrete is significantly higher than that on the flexural properties of concrete beams, and the corresponding degradation ratio between them is maintained at about 1.5. The effect of chloride salt dry-wet cycles on concrete compressive strength is 1.8 times higher than that on the flexural load carrying capacity of test beams. Combined with the test data proposed in this paper and some existing studies, the influence of compressive strength loss on the flexural load carrying capacity of marine concrete beams was discussed. The analysis shows that the compressive strength loss rate can effectively reflect the remaining flexural load carrying capacity of marine concrete beams and there is an exponential relationship between them.
Abstract
To investigate the effect of repeated loading on the flexural load carrying capacity of marine concrete beams suffering from chloride attack, a total of 10 marine concrete [...]
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Monitoring Steel Rebar Corrosion-induced Cracking in ECC Cover byDOFS
E. Chen, H. Ye, S. Zhang

DBMC 2023.

Abstract
Steel corrosion is the main threat to the durability of concrete structures, and the cracking or spalling of concrete cover caused by the expansion of corroded steel can largely accelerate the deterioration process. Engineered cementitious composites (ECCs), as one type of high-performance fiber-reinforced cementitious composites with high tensile ductility and excellent ability of crack width control, have a great potential to be able to improve the durability of structures under corrosive environment. Nevertheless, corrosion of steel rebar may still happen in ECC if aggressive agents depassivate the rebar; therefore, the relationship between the corrosion level and cracking degree in ECC cover is essential for accurately estimating the corrosion condition as well as service life of steel reinforced ECC structures. This study investigates the cracking process of ECC under accelerated steel corrosion implemented by impressed current, during which the distributed optical fiber sensors (DOFS) were employed both on the steel rebar surface and surface of ECC specimens to monitor the internal strain and surface strain generated by the corrosion expansion. The results show that DOFS provide an effective non-destructive tool for detecting the corrosion of steel rebar at early stage when the surface cracks in ECC are not visible.
Abstract
Steel corrosion is the main threat to the durability of concrete structures, and the cracking or spalling of concrete cover caused by the expansion of corroded steel can largely [...]
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Evaluation of Alteration in Cement Paste Due to Calcium Leaching withIntegrated CT-XRD Method and Its Effect on Ionic Diffusions
Y. Tan, T. Sugiyama, K. Hashimoto

DBMC 2023.

Abstract
In 2011, Tohoku earthquake and subsequent tsunami hit Fukushima Daiichi Nuclear Power Plant, and they lead to Fukushima nuclear disaster. For more than a decade after the disaster, concrete materials in submerged structures of nuclear power plants have been chronically in contact with water and resulted in calcium leaching. To assess the alteration of the concrete property, it’s necessary to evaluate the permeability change due to calcium leaching and its effect on radioactive ion diffusion. In this study, small scale cylindrical cement paste specimens with 3mm in diameter and 6mm in height were prepared with water to cement ratios of 0.5 and 0.6 respectively, and they were tested in the static leaching. Specimens were subjected to carbonation before immersed into deionized water for different periods. CT image of each specimen at a resolution of 2.46μm/voxel was acquired in SPring-8, Hyogo, Japan. Combining CT images and X-ray diffraction data, dissolution front of portlandite under different leaching periods was determined, and the time dependent development law of dissolution front was evaluated. Introducing Buil’s model as a local equilibrium, time and position dependent porosity of cement paste due to leaching was calculated and correspondingly diffusion coefficient of Sr ion in the numerical simulation was modified. Simulative results on Sr ion diffusivity for 10-year showed the impact of carbonation followed by leaching on radioactive ion diffusion.
Abstract
In 2011, Tohoku earthquake and subsequent tsunami hit Fukushima Daiichi Nuclear Power Plant, and they lead to Fukushima nuclear disaster. For more than a decade after the [...]
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Evaluating the Corrosion Level of Bare Steel Bars with Pitting Corrosionby DOFS
S. Zhang, Y. Li

DBMC 2023.

Abstract
Steel corrosion is one of the main causes of the deterioration of reinforced concrete structures. Localized pitting corrosion of rebar is particularly harmful, as it can severely damage mechanical properties of steel rebar including both the load and deformation capacities. Moreover, unlike uniform corrosion which can give a warning by causing extensive longitudinal cracking, pitting corrosion is often more hidden with the absence of obvious corrosion cracks. Traditional non-destructive methods based on electrochemistry may encounter large errors when estimating the pitting corrosion level in concrete; as a result, more effective methods/tools are in necessity for a timely and accurate detection of localized pitting corrosion. This study investigates the ability of distributed optical fiber sensors (DOFS) to measure pitting corrosion of steel bars, which is based on the principle that pitting corrosion causes strain localization of steel bar under tension and DOFS enable to capture the strain distribution with high spatial resolution. DOFS were attached on bare steel bars, which have mechanical notches to simulate corrosion pits, to measure the strain distribution along the notched bars under direct tension. Through experiments, the present study explores the possibility of attaching DOFS on the surface of a steel bar to monitor its pitting corrosion, and the positive results are of interest to the development of non-destructive detection method of steel pitting corrosion in concrete structures. Further quantitative analysis is required to find the correlations between the strain distribution along the notched bars and notch geometries, so that the pitting corrosion level could be assessed from the monitored DOFS strains of rebar.
Abstract
Steel corrosion is one of the main causes of the deterioration of reinforced concrete structures. Localized pitting corrosion of rebar is particularly harmful, as it can severely [...]
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Research on the Corrosion Behavior and Cathodic Protection of Defected-Epoxy-coated Reinforcement Exposed to Chloride Environment
D. Zhang, G. Liu, Z. Fan

DBMC 2023.

Abstract
The application of epoxy coated rebar (ECR) is an effective method to improve the durability of reinforcement in chloride environment. However, the coating defects caused in construction will significantly decrease its corrosion resistance to chloride. Herein, the corrosion behaviors of different defects rate in ECR under chloride attack in South China are investigated. The results indicate that the corrosion of ECR is due to the coating defects, the corrosion potentials of defected-ECR are shifted to negative, and the corrosion current density is significantly increased with increasing the defect rate. The corrosion resistance of defected-ECR is improved by applying the anode-mortar cathodic protection system, both the exposure test and engineering application all show that the durability of defected-ECR is increased with the high polarization potential (≥ 200mV) and negative protection potential (＜-800 mV).
Abstract
The application of epoxy coated rebar (ECR) is an effective method to improve the durability of reinforcement in chloride environment. However, the coating defects caused [...]
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Hygrothermal Behaviour of Non-traditional Mortars and ConcretesEva Barreira1, Ricardo M.S.F. Almeida1,2 and Margarida Pais
E. Barreira, R. Almeida, M. Pais

DBMC 2023.

Abstract
In 2015, the European Commission adopted a Circular Economy Action Plan to stimulate the transition of European countries towards the circular economy. In the 2030 Agenda, which includes the 17 Sustainable Development Goals, the United Nations has also defined targets to be implemented by the construction sector based on circular economy concepts. In this context, the importance of directing the development of the construction sector towards sustainable solutions to address the challenges of energy consumption, climate change, resource reduction and waste production is undeniable. Waste incorporation in thermal mortars is already under study by several authors. Among the possibilities of producing sustainable mortars, the reduction of natural aggregates in their preparation, such as sand, or of binders, such as cement, stands out. The incorporation of residual materials in mortars is, therefore, a possible alternative to guarantee more sustainable solutions. The objective of this work was to evaluate the hygrothermal behaviour of non-traditional mortars and concretes, such as fibre-reinforced mortar (P1); sprayable thermal insulation mortar (P2); mortar with granulated cork (P3); concrete with expanded clay (P4); concrete with metallic fibres (P5); cement mortar with construction and demolition waste (P6). The thermal conductivity of these materials, with different moisture contents, from totally dry to saturated after 24 hours of total immersion was determined. The results showed that the thermal conductivity values of the dry materials were similar to those found in the literature. After the 24 hours of humidification, there was, as expected, an increase in mass, with a minimum of 2% for specimen P3 and a maximum of 51% for specimen P2. Regarding the thermal conductivity, there was also an increase in its value for higher moisture contents, being that increase more relevant in specimen P2, with a variation of 294%, and less relevant in specimen P5, with a variation of 18%.
Abstract
In 2015, the European Commission adopted a Circular Economy Action Plan to stimulate the transition of European countries towards the circular economy. In the 2030 Agenda, [...]
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Experimental Study on Macro-performance of Long-age HydraulicConcrete Based on High Temperature Accelerated Curing
Z. Li, Y. Huang, Z. Liao

DBMC 2023.

Abstract
In view of time-consuming and expensive for the long-age mechanical property test of hydraulic concrete, the change rule for the mechanical properties of hydraulic concrete with long-age is still unclear. Based on the equivalent age theory, the high-temperature curing method was employed to accelerate test. First, the macro-mechanical properties tests of hydraulic concrete at different curing ages (90d, 180d, 1a, 2a, 3a) and different fly ash contents (0%, 15%, 35%) were designed and carried out. Then the change rule of mechanical properties of hydraulic concrete at long-age were analyzed. In addition, the macro test results of concrete core specimen of a gravity dam which has been operated more than 40 years were adopted to feedback the above test results. The research results showed that the fly ash content had a significant influence on the activation energy Ea of hydraulic concrete. To reach the same hydration degree of design long-age, the curing time increased with the increasing of fly ash content. Within the curing age of 3a, the compressive and splitting tensile strength of concrete increased with the increasing of curing age. The strength values of cement concrete and concrete with 15% fly ash content were close to each other, while the strength values of concrete with 35% fly ash content were smaller than the cement concrete and concrete with 15% fly ash content. The consistency and reliability of the rule that the concrete strength continues to increase with age was further verified by combining the macroscopic test results and the strength growth rate calculation results of a gravity dam concrete core specimen that had been in service for more than 40 years.
Abstract
In view of time-consuming and expensive for the long-age mechanical property test of hydraulic concrete, the change rule for the mechanical properties of hydraulic concrete [...]
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Evaluating the Energy and Mechanical Properties of CSH/nano-CC Interface: An Atomic Investigation
R. Wen, Q. Zeng, B. Gao

DBMC 2023.

Abstract
Carbonation of concrete generally leads to decalcification of calcium silicate hydrates (CSH) and generation of calcium carbonate (CC), however, the structure and mechanical properties of CSHCC nano composites are far from being fully addressed. The CC formed by CSH carbonization mainly has three polymorphs, including calcite, vaterite and aragonite. Although different polymorphs have the same chemical composition, they belong to different crystal systems and have completely different unit cell structures. In this paper, the CSH and three polymorphs nano-CC are constructed at the atomic level, and the interface properties between them are explored by reactive molecular dynamics (MD) simulations. The results show the greater interfacial bonding energy, the better the mechanical properties of the CSH-CC composite. Moreover, interface transition region (ITR) emerges between CSH and CC polymorphs, and the ITR thickness is different. The atomic structure in ITR is different from that in the middle region, the former is more disorderly and the coordination number in ITR is significantly reduced, thus showing a metastable state. The findings would deepen the mechanistic understanding of interface properties between CSH and nano-CC.
Abstract
Carbonation of concrete generally leads to decalcification of calcium silicate hydrates (CSH) and generation of calcium carbonate (CC), however, the structure and mechanical [...]
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Damage Process Assessment of Mortar Samples under Freeze-thaw Cycleswith Micro-CT and Expansion Measurements
J. Xi, Y. Takahashi, Y. Kawabata

DBMC 2023.

Abstract
The aim of this study is to comprehensively investigate the relationship between 3- dimensional crack development and mechanical degradation during Freeze-thaw cycles (FTC). An FTC test was designed in this study to relate the micro-scale crack patterns to the macro-scale expansion and mechanical property deterioration at different FTC damage levels. Mortar specimens with waterto-cement (w/c) ratios of 50% and 75% were cast in two sizes (i.e., Ø5×10 cm, Ø2×2.5 cm) and were subjected to FTCs. For Ø5×10 cm specimens, strain in the center part of the specimens were monitored by embedded mold gauges and compression tests were conducted at different expansion levels. For Ø2×2.5 cm specimens, X-ray micro computed tomography (micro-CT) and compression tests were conducted after different FTC durations. By comparing the test results of these two groups of specimens, the expansion, mechanical degradation, and development of micro-cracks in the mortar specimens during the FTC damage process were correlated. It is indicated that with similar mechanical reduction, the damage pattern differs in two w/c cases. This research provides a test method for investigating internal swelling damage and proposes the direction for further improvement of FTC simulation model.
Abstract
The aim of this study is to comprehensively investigate the relationship between 3- dimensional crack development and mechanical degradation during Freeze-thaw cycles (FTC). [...]
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Sensitivity of Capillary Absorption and Sorptivity to Water Retention, Permeability and Other Relevant Characteristics for Cement Mortars
Y. Zhang, F. Ren, C. Zhou

DBMC 2023.

Abstract
Concrete materials and structures are neither totally saturated nor dry, making the efficient capillary absorption of water deserve much attention. Basically, absorption of water is a process of unsaturated permeation driven by capillary pressure. This dependence of capillary pressure on water content plays an essential role in predicting capillary absorption and thus calculating sorptivity, which is also affected by inherent permeability, tortuosity coefficient significantly. Considering the evolution of pore structure of cement-based materials (CBMs) upon wetting, the long-term absorption of water into mortars and sorptivity can be predicted. However, a few investigations have been done to understand the precision of measured sorptivity, which is tried numerically in this paper focusing on the influences of varying parameters including water retention characteristics, tortuosity parameter, inherent permeability and swelling time. Based on reported experimental data of two cement mortars, 100 curves of capillary absorption in 10 days are predicted with artificially random parameters. Both the first and secondary sorptivity are further calculated and evaluated with emphases on the coefficient of variation of sorptivity and its sensitivity to varying parameters. Water retention characteristics make certain contribution to the dispersion of both initial and secondary sorptivity. Sorptivity is also sensitive to the variations of porosity and tortuosity representing the heterogeneity of their pore structure. The swelling time brings observable effects on the precision of secondary sorptivity only.
Abstract
Concrete materials and structures are neither totally saturated nor dry, making the efficient capillary absorption of water deserve much attention. Basically, absorption of [...]
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Application of Ultrasonic Computerized Tomography Technique to Detect the Internal Defects in Cement-based Mortar
Z. Li, K. Li, J. Wang, L. Li

DBMC 2023.

Abstract
It is widely acknowledged that ultrasonic technology provides a considerable detection approach while describing the internal fractures in concrete, which is a serious issue when evaluating the durability performance of cement-based materials. This paper aims to introduce the work which is concerned with the use of ultrasonic computerized tomography (UCT) technique to evaluate the micro-cracks inside mortar. The result shows that UCT is a relatively promising method which is capable of imaging the positions of tiny cracks and local damage, moreover, the application of X-ray computerized tomography (XCT) also verifies the accuracy and reliability of UCT. Effective evaluating the internal cracks depends on the detection of attenuation of ultrasonic signals that perpendicular to internal cracks, furthermore, ultrasonic technology is more likely to detect the crack with larger surface of damage, but not sensitive to local fracture.
Abstract
It is widely acknowledged that ultrasonic technology provides a considerable detection approach while describing the internal fractures in concrete, which is a serious issue [...]
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Experimental Evaluation of Flexural Strength and Ductility of One-Way Concrete Slab Panels Reinforced with Welded Wires and Deformed Bars
M. Mahdi, F. Ahmed, I. Ahmed, N. Islam

DBMC 2023.

Abstract
This study evaluates the flexural strength and ductility of one-way concrete slab panels reinforced with deformed bar and welded wire under the application of pure bending. An experimental database of flexural strength and ductility for a set of three slab panels reinforced with 10 mm deformed bar, three panels with 6 mm welded wire reinforcement (WWR), and three panels with 8 mm WWR has been developed, with each slab panel having a dimension of 762 mm by 2286 mm. The deflection and ductility factors of the specimens are investigated. The results show that the slab panels reinforced with 6 mm WWR exhibit less vertical deflection at fracture in comparison to those with 8 mm WWR. Welded wire reinforced slab panels demonstrated uniformly distributed crack propagation in comparison to deformed bars. In addition, the slab panels with 8 mm WWR exhibit higher flexural strength than the 6 mm WWR reinforced panels. The 10 mm deformed bar-reinforced slab panels exhibited greater deflection at fracture compared to WWR specimens. The reason for the lower ductile behavior of slab panels with 6 mm WWR is due to the fact that 6 mm WWR, produced locally in Bangladesh, is manufactured by the cold-drawn method and has a lower ductility in compliance with BDS ISO 6935 Class A, which does not conform to ASTM A1064. Both 8 mm WWR and 10 mm deformed bars conform to BDS ISO 6935 Class D and ASTM A1064. Hence, the 6 mm WWR with Class A ductility is not recommended for reinforced concrete (RC) slab panels based on the experimental results conducted in this study, whereas the 8 mm WWR and the 10 mm deformed bar with Class D ductility are suitable for structural use as recommended in ACI 318.
Abstract
This study evaluates the flexural strength and ductility of one-way concrete slab panels reinforced with deformed bar and welded wire under the application of pure bending. [...]
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Pitfalls in Using Electrical Conductivity to Monitor the Chloride Ingress of Concrete
L. Huang, L. Tang, Z. Yang

DBMC 2023.

Abstract
Chloride ingress in the field structure is influenced by many factors. A non-destructive monitoring is a useful tool for assessing the health of reinforced structures. This study used array sensors to measure the temperature and electrical conductivity of concrete at depths from 10 mm to 140 mm. The electrical conductivity in concrete showed a continuous decrease during the exposure to 3% NaCl solution. A numerical modelling of multi-ion species migration in pore solution can explain the evolution of conductivity profile over exposing time. By comparing with several previous investigations, this study identified the pitfalls in using electrical conductivity or resistivity to monitor the chloride ingress in the exposed concrete. To obtain a correct information from the electrical monitoring system, the experimental and analysing process should consider the saturation degree of concrete, the hydration induced structure change, the leaching of ions, the ingress of chloride and composition of binders.
Abstract
Chloride ingress in the field structure is influenced by many factors. A non-destructive monitoring is a useful tool for assessing the health of reinforced structures. This [...]
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Corrosion Mechanisms of Reinforced Alkali-Activated Concrete
F. Zhang, S. Yang

DBMC 2023.

Abstract
Alkali-activated concrete (AAC), which exhibits good mechanical strength and chemical resistance properties, has attracted emerging interest from the research perspective considering the sustainable development of construction materials. However, the corrosion mechanism at the steel-AAC interface is not yet well understood including the physical and chemical aspects, which leads to different accumulation and evaluation of corrosion products, compared to ordinary Portland cement (OPC) concrete. In this paper, concrete pull-out test and electrochemical techniques were used to investigate the bond-slip behaviour and the evolution of deterioration of AAC respectively. In addition, the current guidance of corrosion evaluation used for OPC concrete based on ASTM C876 is not suitable for AAC. Five mixed ratios of blended fly ash and slag AAC were investigated under two chloride environments and one non-chloride environment, i.e., (1) 3.5% NaCl salt fog spray in the environmental chamber; (2) 3.5% NaCl saltwater immersion; (3) tap water immersion. Electrochemical techniques include half-cell potential, linear polarization resistance and Tafel extrapolation method were used to determine the corrosion rate. The electrochemical results are validated through the comparison of the gravimetric loss of steel after corrosion and electrochemical loss from calculation.
Abstract
Alkali-activated concrete (AAC), which exhibits good mechanical strength and chemical resistance properties, has attracted emerging interest from the research perspective [...]
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Effect of Moisture History on ASR Expansion and Microstructural Properties
O. Olajide, M. Nokken, L. Sanchez

DBMC 2023.

Abstract
Alkali Silica reaction has been a great menace to the durability of concrete infrastructure since its discovery. The mechanism is caused by the reaction between poorly crystallized silica and alkalis in the presence of sufficient amount of water. Just as water plays a critical role in several durability challenges in concrete, the limitation of moisture has been prominently used as a technique for the maintenance of ASR affected structures. The variation in moisture condition to which structures are exposed could lead to alternate wet and dry regimes. Drying aids the mitigation of the reaction, however, the cyclic phenomenon can modify the kinetics of the reaction and exercebate inner damage. This paper focuses on the development of the reaction over an alternate wetting and drying cycle involving aggregates of different levels of reactivity. The influence of the moisture history on the microscopic features were appraised using the damage rating index. The kinetics of the reaction and ASR induced deterioration in specimens undergoing cycles of wet and dry conditions differ when compared to those stored at constant moisture. Furthermore, ASR induced expansion and petrographic features are influenced by the difference in the reactivity level of aggregates.
Abstract
Alkali Silica reaction has been a great menace to the durability of concrete infrastructure since its discovery. The mechanism is caused by the reaction between poorly crystallized [...]
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Comparison Between Parameters of Corrosion, Obtained by Destructive and Non-destructive Electrochemical Techniques
C. Alves, A. Oliveira, T. Cardoso, O. Cascudo

DBMC 2023.

Abstract
This research aims to compare corrosion parameters obtained by linear polarization technique and Tafel extrapolation method in steel bars embedded in concrete. It was analyzing the intervention of mineral additions, such as metakaolin (10%) in binary concrete mixtures and silica fume (9% ) and nano silica (1%) in ternary concrete mixtures of water/binder ratio of 0.4 and 0.6 after induction of corrosion by wetting and drying cycles in a solution containing chlorides. Thus, the corrosion potential (Ecorr), polarization resistance (Rp) and corrosion rate (icorr) were measured. As a main result, a good correlation (R² of 0.82 and 0.96) was obtained with the values of polarization resistance (Rp) and corrosion rate (icorr), obtained by Rp and by Tafel slope, respectively. Binary and ternary concretes mixtures showed higher performance than reference concretes. Reference concrete with w/ratio of 0.6 showed a high corrosion rate.
Abstract
This research aims to compare corrosion parameters obtained by linear polarization technique and Tafel extrapolation method in steel bars embedded in concrete. It was analyzing [...]
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Durability of Concrete and Reinforced Concrete Structures Subjected to Temperature Cycles: Insight from Multiscale Thermomechanical Analysis
B. Pichler

DBMC 2023.

Abstract
This document refers to thermal expansion of cementitious materials and to related thermal stresses activated in samples of concrete as well as in unreinforced and reinforced concrete structures. It provides an overview of multiscale research which was carried at the Institute for Mechanics of Materials and Structures, TU Wien, Vienna, Austria, in cooperation with Tongji University and Shanghai Jiao Tong University, China. The overview starts with the nanoscopic origin of the thermal expansion behavior of cement paste, which is triggered by the heating-induced release and the cooling-induced uptake of water by calcium-silicate-hydrates (C-S-H). Temperature changes lead to thermal strains. Thermal stresses are activated provided that the thermal strains are constrained. Such constraints prevail at microstructural scales of concrete as well as at cross-sectional and macrostructural scales of unreinforced and reinforced concrete structures such as beams, plates, and frames. Diurnal temperature changes result in daily cycles of self-equilibrated thermal stresses. They represent a considerable loading for interfacial transition zones (ITZs) separating the aggregates from the cement paste matrix. Extreme events such as sudden hail showers or moderate fires are very likely to result in thermal cracking, at least in the microscopic region of the ITZ, but frequently also at the larger scale of concrete.
Abstract
This document refers to thermal expansion of cementitious materials and to related thermal stresses activated in samples of concrete as well as in unreinforced and reinforced [...]
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Influence of Coarse Aggregate Grade on Air Void Structure of Air-entrained Concrete
Q. Liu, J. Kong

DBMC 2023.

Abstract
Air void structure has always been a key factor affecting the frost resistance of concrete. The refinement of air void structure mainly comes from the extrusion of slurry and the cutting of aggregates. However, there is no systematic theory on the influence of aggregate on air void structure. In this paper, the effects of different coarse aggregate grades on the concrete air void structure were studied. The fractal dimension D value was used to represent the coarse aggregate gradation. In the range of coarse aggregate particle size between 4.75-26.5 mm, D=2.1, D=2.3, D=2.5, D=2.7 were selected as the experimental group, and single-graded coarse aggregate of 4.75 and 26.5 mm were selected as the control group, with a total of six test groups. By means of an air content tester, Rapid Air, freeze-thaw durability test and other measurements, the air content, air void structure, freeze-thaw durability and other performance parameters were measured. The differences in air void structure parameters of specimens, such as air content, spacing factor and the number of bubbles were compared to obtain the relationship between the coarse aggregate grading and air void structure. Further analysis of its influence on frost resistance can provide a reference for scientific research and engineering application of concrete air void structure.
Abstract
Air void structure has always been a key factor affecting the frost resistance of concrete. The refinement of air void structure mainly comes from the extrusion of slurry [...]
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Efficiency Evaluation of Metakaolins for Use in Concrete
H. Carasek, P. Passos, O. Cascudo

DBMC 2023.

Abstract
The use of metakaolins has been shown to be effective in modifying the properties of cementitious materials related to durability, highlighting the very positive impact in terms of increasing the electrical resistivity of concrete and reducing ionic transport in this porous medium. In this sense, the present work aims to evaluate the efficiency of different metakaolins in terms of pozzolanic activity, linking the efficiency to various characteristics of the metakaolin. Five samples of different Brazilian commercial metakaolins were then characterized, using the following methods: BET specific surface area, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, thermal analysis (TA/DTA), thermogravimetric analysis (TG/DTG) and determination of pozzolanic activity by the modified Chapèlle method. As the main results, it was found that the BET specific surface area and the Al2O3 content, obtained by XRF, better explain the pozzolanic activity of metakaolins (Pearson correlation coefficients equal to 0.89 and 0.94, respectively). The amorphous content (quantified by Rietveld in the XRD) showed only a reasonable correlation with the pozzolanic activity determined by the modified Chapèlle method. In general, the chemical-mineralogical characteristics that indicate purity and amorphism of metakaolin, expressed by the Al2O3 content, Al2O3/SiO2 ratio, SiO2+Al2O3 sum, and amorphous content, represent important performance parameters of metakaolins. The specific surface area compensates for lower purity or chemical reactivity and significantly influences pozzolanic activity.
Abstract
The use of metakaolins has been shown to be effective in modifying the properties of cementitious materials related to durability, highlighting the very positive impact in [...]
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Reinforced Concretes of Tomorrow: Corrosion Behaviour according to Exposure Classes
V. Bouteiller, E. Marie-Victoire, A. Bonnet, V. Da-Silva, L. Adelaïde, J. Billo, C. Da-Costa, M. Bouichou, J. Ducasse-Lapeyrusse, J. Mai-Nhu, P. Barthélémy, P. Turcry, F. Cussigh, S. Chanut

DBMC 2023.

Abstract
Reinforced concrete is the most widely used building material but its durability in terms of concrete cover performance and corrosion of steel rebar is still a key point to be studied. To address this topic, within the frame of the national project PERFDUB, two series of eleven reinforced concrete specimens (with metric dimensions) were cast with innovative concrete mixes representative of the French experience, two shapes of rebar and two concrete covers. Then, these specimens were exposed in two natural exposure sites, one in Epernon for carbonation (XC4) and a second one in La Rochelle in the Atlantic Ocean in a tidal zone for chloride ions (XS3m). Their corrosion was carried out using non-destructive testing. In addition, in order to follow the corrosion evolution more accurately in a continuous way, two series of three specimens were casted with embedded sensors and were exposed in two other outdoor sites in Marne-la-Vallée (XC4) and in Eqiom facility (XS3e). The first results of this 20-year project in terms of corrosion of these reinforced concrete specimens obtained with laboratory and field equipment and with monitoring are presented in this paper.
Abstract
Reinforced concrete is the most widely used building material but its durability in terms of concrete cover performance and corrosion of steel rebar is still a key point to [...]
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Hydrophobicity Mechanism of Cementitious Material Containing Carboxylic Acid Ammonium
H. Zhang, S. Mu, J. Cai, J. Hong

DBMC 2023.

Abstract
Hydrophobic treatment of cement pastes is most effective way to resist the penetration of water with aggressive ions to improve durability of cement-based materials. In this paper, the mechanism of carboxylic acid ammonium salt integral additionon hydrophobicity of cement-based materials is analyzed. The effects of carboxylic acid ammonium salt on hydrophobicity, moisture diffusion and hydration products are investigated by experimental methods.The results of water vapor sorption isotherm show that the addition of carboxylic acid ammonium salt increases the pore volume. The simplified analytical hydrodynamic model of cone type pore and Young’s relationship is proposed to analyze the relation between characteristic parameters of pore and the permeability of cementitious materials. It can be concluded that the hydrophobicity results from the change of pore structure and the hydrophobic surface of cone region. These results provide the guidance to design the durability and develop the new hydrophobic agent used in cementitious material.
Abstract
Hydrophobic treatment of cement pastes is most effective way to resist the penetration of water with aggressive ions to improve durability of cement-based materials. In this [...]
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Accelerated Degradation of Coating-mortar Interface under UV Radiation in Presence of Water
Y. Dai, Q. Zeng

DBMC 2023.

Abstract
The application of organic coatings is one of the most effective and economic methods to protect concrete structures from deterioration. However, organic coatings are prone to degradation under aggressive environmental actions, so the protective function may loss. While ultraviolet (UV) aging is often blamed for the degradation of organic coatings, water may play a more important role on the interfacial adhesion between the coatings and the substrate. To uncover the effect of water on the degradation performance of coating-substrate system, mortar samples coated with water-borne epoxy resin (WER) were exposed to three assigned environments, i.e., UV radiation, UV/water immersion, and UV/dry-wet cycle, up to 60 days. The surface appearance, chemical structure, wettability, and surface micro-morphology of the aged WER coatings were characterized via image process analysis, attenuated total reflectance flourier transform infrared spectroscopy (ATR–FTIR), static water contact angle, and scanning electronic microscopy (SEM). Results show that the UV/water immersion resulted in severest blistering on the WER-mortar interface, while the UV/wet-dry cycle caused the formation of micro-pinholes on the WER surface. In contrast, the UV radiation did not induce such severe aging. The data implied that water can accelerate the aging of WER-mortar system.
Abstract
The application of organic coatings is one of the most effective and economic methods to protect concrete structures from deterioration. However, organic coatings are prone [...]
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Accelerating Effect of Heating Treatment on the Damage of Cement Paste under Sulfate Attack
B. Ran, O. Metalssi, T. Fen-Chong, P. Dangla, K. Li

DBMC 2023.

Abstract
The ettringite (AFt) formation and damage process are investigated for cement paste subjected to external sulfate attack with and without heating treatment during curing. Slice and disc specimens were exposed to 10 g/L Na2SO4 + pH of 13. The evolutions of AFt formation, pore structure, and expansion on slice specimens were characterized through 27Al NMR, MIP, and micrometer. The surface cracks on disc specimens were observed through an optical microscope. The experimental results show that: (1) heating treatment dissolves part of AFt and accelerates the ettringite formation and material expansion; and (2) heating treatment initiates the microcracks, thus promoting the material cracking.
Abstract
The ettringite (AFt) formation and damage process are investigated for cement paste subjected to external sulfate attack with and without heating treatment during curing. [...]
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Degradation of Cement Pastes Subjected to Combined Carbonation and Leaching
Q. Phung, L. Frederickx, N. Maes

DBMC 2023.

Abstract
Carbonation and leaching are likely to be the primary concrete degradation mechanisms for concrete utilized in geological repositories when the concrete is fully saturated and in contact with host rock pore water containing increased CO2 content. This work describes the changes in the microstructure and transport properties of cement pastes caused by coupled chemical degradation processes that occur at the cement paste-clay interface. In the laboratory, an experimental program was designed to accelerate the interface interaction under carbonation and leaching by bringing highly porous cement pastes (to mimic backfill materials used in geological disposal) and Boom Clay into contact in either accelerated percolation or batch-type experiments. Mercury intrusion porosimetry (MIP) was used to investigate the microstructural alteration. Inductively coupled plasma optical emission spectrometer (ICP-OES) and permeability, diffusion measurements were used to determine the evolution of chemical and transport properties, respectively. The results of the porosity change at the interface demonstrate an increase in porosity of the cement paste interface due to Ca leaching, which overwhelms the carbonation. As a result, the transport properties increase. This suggests that clogging of the cementitious material side is unlikely.
Abstract
Carbonation and leaching are likely to be the primary concrete degradation mechanisms for concrete utilized in geological repositories when the concrete is fully saturated [...]
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Cement Degradation Caused Risks for Geological Carbon Sequestration Reservoirs
X. Shi, M. Wu

DBMC 2023.

Abstract
Geologic carbon sequestration (GCS), a process to capture and store CO2 in deep geologic formations, is considered an essential technique to reduce carbon emissions which are a main cause of global warming and climate change. Depleted oil and gas reservoirs are among the most appealing locations for GCS. However, the success of the strategy relies on the long-term integrity of the reservoirs, which is challenged by the carbonation reactions between the main reservoir sealing material, i.e., cement, and the stored CO2 and then the occurrence of fluid leakage. This work provides a concise review on the degradation of oil well cement and the interface between cement and casing/formation rock, with a special focus on the influence of different factors such as the curing, service conditions and contaminants. The mechanisms and the mitigation methods of the degradation process are also discussed. This work aims to summarise current research progress and identify some remaining challenges for future research.
Abstract
Geologic carbon sequestration (GCS), a process to capture and store CO2 in deep geologic formations, is considered an essential technique to reduce carbon emissions which [...]
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Durability of GFRP and BFRP Bars in Sulfoaluminate Cement Concrete Made with Seawater and Sea Sand
T. Wang, A. Razaqpur

DBMC 2023.

Abstract
Due to the large carbon footprint of ordinary Portland cement (OPC) and the rapid corrosion of steel rebars in certain environments, the search for greener, sustainable and more durable reinforced concrete structures is ongoing. In this study, the alkali resistance of basalt- and glass-fibre reinforced polymer (BFRP/GFRP) bars in sulfoaluminate cement (SAC) concrete made with seawater and sea sand is investigated for the first time. Production of SAC involves lower energy consumption and greenhouse gas emission compared to OPC while SAC concrete provides a lower pH environment, which favors the durability of FRP bars. Following ASTM D 7705-D7705M-12 Procedure A, the bars were immersed for three months in simulated pore solution of concrete made with SAC, river sand and fresh water, termed Solution A, and compared their durability to that of companion bars immersed in simulated pore solution of concrete made with SAC, seawater, and sea sand, termed Solution B. Both solutions had the same pH, and their temperature was maintained at 60℃ for the duration of the test. The post-immersion or retained tensile strength of GFRP bars in Solution A and B was 83.0% and 73.6%, respectively, while the corresponding values for the BFRP bars were 52.5% and 67.9%, respectively. It appears that due to the presence of sea salt, Solution B is less damaging to BFRP than Solution A while the opposite is true in the case of GFRP. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) results are utilized to explain the damage mechanisms. Based on image analysis, it is shown that the deteriorated zone within the bar cross-section is not a uniform ring, but its cross-sectional area correlates with the reduction in tensile strength.
Abstract
Due to the large carbon footprint of ordinary Portland cement (OPC) and the rapid corrosion of steel rebars in certain environments, the search for greener, sustainable and [...]
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Study of the Chemical Processes of Combined Sulfate-chloride Attack on Low-carbon Cementitious Materials
F. El Inaty, M. Marchetti, M. Quiertant, O. Omikrine-Metalssi

DBMC 2023.

Abstract
In marine environments, concrete structures are not only exposed to sulfate ions but also to chloride ones, from an early age. This leads to concrete expansion and cracking as well as steel reinforcements corrosion. However, the coupling effect of sulfate and chloride is still not widely studied. When addressed, some researchers showed that chloride ions mitigate the effect of sulfate while others concluded that it accelerates it and vice versa. Therefore, one of the objectives of this study is to observe both the combined and individual effects of chloride on sulfate attack. The second objective is to perceive the resistance of selected additives (fly ash, blast furnace slag, and metakaolin) to a combined attack. Then, powders of pure cement, binary, ternary, and quaternary blended pastes were immersed in sulfate, chloride, and sulfate-chloride solutions at an early age. Results of the characterization showed that the ettringite formation was delayed due to the presence of chloride. However, the presence of sulfate ions accelerated the chloride effect. The incorporation of more than one additive enhanced the samples’ durability.
Abstract
In marine environments, concrete structures are not only exposed to sulfate ions but also to chloride ones, from an early age. This leads to concrete expansion and cracking [...]
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Mineralogical Characterization of the Biodegradation of Sewage Cementitious Materials in the Presence of H2S
J. Ayoub, T. Pons, M. Guéguen Minerbe, M. Oliveira, M. Marchetti

DBMC 2023.

Abstract
The biodegradation of cementitious materials in sewage systems is mainly due to the biotic oxidation of hydrogen sulfide (H2S) into sulfuric acid. It leads to a local and progressive dissolution of the cementitious matrix as well as the precipitation of some expansive products such as gypsum and ettringite. In such a context, this paper focuses on the characterization of the altered layers present on several types of cementitious materials (CEM I ordinary Portland cement, CEM III blast furnace cement, CEM V composite cement, and CAC: calcium aluminate cement). The studied samples are mortars exposed, to different H2S concentrations, for several years in a local sewage plant managed by the Interdepartmental Syndicate for the Sanitation of the Paris Agglomeration (SIAAP). Transversal crosssections of these mortars were first chemically characterized by energy dispersive spectroscopy (EDS) in order to obtain elemental mapping. Additionally, to better understand the surface degradation and the appearance of mineral phases revealing the process, µ-Raman mappings were performed on the deteriorated zones at different time scales. Gypsum was observed on all samples. The analysis confirmed the greater resistance of CAC materials in such an environment than that of Portland cement-based materials.
Abstract
The biodegradation of cementitious materials in sewage systems is mainly due to the biotic oxidation of hydrogen sulfide (H2S) into sulfuric acid. It leads to a local and [...]
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Hysteretic and Scanning Behaviors of Water Vapor Sorption in Hardened Cement Pastes
Z. Wang, K. Li

DBMC 2023.

Abstract
Water in the multiscale porous microstructure of cement-based materials is closely related to multiple deterioration processes, hence significantly influences the durability of concrete structures in atmospheric environment. Water vapor sorption is the key tool for characterizing the hygroscopic properties of cement-based materials, also a promising technique for exploring their nanopore structures. The significant hysteresis between different sorption branches is stemmed from the complexity of interconnecting pore system and concurrence of different physical phenomena. In this study, the hysteretic and scanning behaviors of water vapor sorption in hardened cement pastes are measured with a dynamic vapor sorption instrument, and investigated to provide new insights into the path-dependency of sorption behaviors on humidity history and resolve the overall sorption hysteresis into contributions from different phenomena.
Abstract
Water in the multiscale porous microstructure of cement-based materials is closely related to multiple deterioration processes, hence significantly influences the durability [...]
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Effect of Electric Field on the Degradation Process of Reinforced Mortar under Chloride and Sulfate Attack
X. Yu, S. Li, X. Chang, Y. Liao, D. Chen

DBMC 2023.

Abstract
This study investigated the degradation mechanism behind the reinforced mortar exposed to chloride, sulfate and electric field. The steel-mortar samples were exposed to 5% Na2SO4, 5% NaCl + 5% Na2SO4 solutions and deionized water in two regimes (full immersion and direct current electric field). The efficiencies of three current densities were compared as well. The total and free sulfate ion content in the mortar were measured. The microstructural analysis by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) were conducted. The results indicated that the electric field drastically increased the ingress of sulfate, as well as the sulfate reaction. Meanwhile, the current attenuated the interaction between chloride and sulfate. The increase in current density decreased the efficiency of degradation acceleration. An acceleration factor (AF) was proposed based on the comparison between the number of ions in the mortar under electric field and immersion. Findings from this study are beneficial to develop a reliable acceleration method for the long-term performance of RC structures under chloride and sulfate attack.
Abstract
This study investigated the degradation mechanism behind the reinforced mortar exposed to chloride, sulfate and electric field. The steel-mortar samples were exposed to 5% [...]
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Dissolution Behaviour of Alkali-activated Fe-rich Non-ferrous Metallurgy Slag in Acetic Acid
N. Wen, V. Hallet, A. Peys, Y. Pontikes

DBMC 2023.

Abstract
The application of Fe-rich non-ferrous metallurgy slag (NFS, within a FeOx-SiO2-Al2O3-CaO system) in alkali-activated materials requires detailed information on the durability performance. The present study investigates the durability of alkali activated NFS (AA-NFS) exposed to acetic acid to simulate the attack of a concrete by organic acids present in animal manure or sewage systems. The dissolution behavior of NFS and alkali-activated NFS (AA-NFS) was assessed by immersing NFS and AA-NFS in a 3 wt. % acetic acid solution at a liquid to solid weight ratio of 1000. The dissolved ions in the acetic solution from NFS and AA-NFS were measured at different time intervals over 7 days. Through the comparison of NFS with AA-NFS, the dissolution behavior of unreacted slag and binder in AA-NFS could be evaluated separately, considering a calculated amount of 47.7 wt.% of unreacted slag was present in the AA-NFS. The results demonstrated that the binder dissolves slightly faster than slag in the first 4 hours. Over half of the dissolution rate of the Ca, Fe and Al in AA-NFS was due to binder. While for Si, 41% total dissolution rate in AA-NFS was from binder and the other 59% was from unreacted slag. After 7 days however, the dissolved fraction of slag was higher than binder. About 90% Ca, 79% Fe and 71% Al in slag was ended up in the acetic acid solution, which is higher than that in binder (74%, 62% and 56%, respectively). A significantly higher difference was found for the total dissolved fraction of Si in slag (86%) compared to that in binder (43%). The highly connected silicate network in the binder remains largely intact as silica gel, while due to the low connectivity of the silicate species in the slag the silicate dissolves after the other elements have left the structure. Overall these results suggest that Ca has the lowest dissolution resistance in binder, followed by Fe, Al and Si.
Abstract
The application of Fe-rich non-ferrous metallurgy slag (NFS, within a FeOx-SiO2-Al2O3-CaO system) in alkali-activated materials requires detailed information on the durability [...]
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Thermal-Resistivity Characteristics of Carbon Fabric Reinforced Cementitious Matrix
Y. Gong, J. Liu, J. Hong, D. Zhang

DBMC 2023.

Abstract
The thermal-resistivity effect of the carbon fiber reinforced cement (CFRC) has been successfully applied to monitor the temperature of concrete structures. There are insufficient studies on the thermal-resistivity effect of the carbon fabric reinforced cementitious matrix (CFRCM). In this paper, the resistance change of CFRCM from room temperature to 120℃ and the thermal-resistivity characteristics during repeated heating have been studied. It was showed that during the heating process, with the continuous increasement of the carrier concentration, the specimen exhibited obvious negative temperature coefficient (NTC) effect, and a temperature rise of 10℃ lessened relative resistance change by about 0.4%. However, some carriers stayed in the conduction band after the first cooling. Then, the resistance cannot return to the original value, and the curves of subsequent heating processes had a good repeatability.
Abstract
The thermal-resistivity effect of the carbon fiber reinforced cement (CFRC) has been successfully applied to monitor the temperature of concrete structures. There are insufficient [...]
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Study on Shrinkage Properties of Repairing Mortar Modified by Basalt Fiber
S. Yang, P. Xu

DBMC 2023.

Abstract
In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four factors, i.e., silica powder, sodium silicate, basalt fiber and a U-type expansive agent, were used to measure the length change ratio. The results show that the shrinkage value of modified repairing mortars have been greatly reduced. Compared with the control specimen without any additives, the shrinkage value of the modified repairing mortar with the silica powder of 3 %, the sodium silicate of 1.0 %, the basalt fiber of 0.2 % and the U-type expansive agent of 10 % at 60d drops by 42.5%. Based on experimental results, the shrinkage prediction model of modified repairing mortar has been established. The model can be used to predict the shrinkage value of the modified repairing mortar with similar compositions.
Abstract
In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four [...]
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Experimental Study on Improvement of Interfacial Bond Properties of Carbon Fiber Reinforced Cement Matrix Composites by Nano Silica
J. Liu, J. Hong, Y. Gong, B. Yi, D. Zhang

DBMC 2023.

Abstract
The fiber reinforcement efficiency of carbon fiber reinforced cement matrix composites (CFRCM) is limited by the low permeability of mortar to internal filaments in the fibers, leading to premature failure of the composites due to low bond strength. In this paper, three kinds of nano-silica materials were used to improve the bond properties of carbon fiber bundles to cement-based matrix by coating and electrophoretic deposition. It is found that different methods have different positive or negative effects on the improvement of bond properties, and the effects are different under different embedded lengths. The modification principle is due to the high impregnation of nano silica particles on the fibers and the reaction of volcanic ash of the particles, which promotes the formation of calcium silicate hydrate gel inside the fibers. Relevant research needs further exploration.
Abstract
The fiber reinforcement efficiency of carbon fiber reinforced cement matrix composites (CFRCM) is limited by the low permeability of mortar to internal filaments in the fibers, [...]
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Electrical Joule Heating and Early Strength of Mineral-impregnated Carbon Fibre Reinforcement (MCF)
W. Dong, M. Liebscher, B. Yang, J. Zhao, V. Mechtcherine

DBMC 2023.

Abstract
Mineral-impregnated carbon fibre reinforcement (MCF) has attracted increasing attention due to its low-cost, easy manufacturing, high temperature and chloride resistance, when it replaces traditional steel reinforcement for concrete construction. Considering its excellent electrical conductivity, this paper investigates the effect of electrical Joule heating on the temperature increase, mechanical and microstructural characteristics of MCF. Different duration of electrical heating ranging from 0.5h, 1h, 2h, 4h to 8h had been explored. In addition, the effect of water spray treatment on the electrically heated MCF will be conducted. For the MCF reference without electrical heating, it is not hardened and the early flexural strength can’t be obtained. The temperature of MCF under the voltage of 15 V gradually increases to 100.5 °C and then keeps stable. The highest early flexural strength of MCF immediately tested after heating reached 290.8 MPa when the electrical heating time is 8h, and with the water spray treatment. Interestingly, the water spray treatment seems to benefit the strength development, with the less generated micro pores around the interfaces of carbon fibres to cement matrix. The results indicate that the rapid hardening MCF subjected to electrical heating can work as self-heating elements or rapid production and transportation of MCF for concrete structures.
Abstract
Mineral-impregnated carbon fibre reinforcement (MCF) has attracted increasing attention due to its low-cost, easy manufacturing, high temperature and chloride resistance, [...]
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Developing Multifunctional Ultra-High Performance Concrete via Incorporating Hybrid Steel Wires and Fibers
S. Dong, X. Wang, B. Han

DBMC 2023.

Abstract
Stainless steel wires (SSWs) with micro diameter and stainless steel fiber (SFs) with millimeter diameter were incorporated together to develop multifunctional ultra-high performance concrete (UHPC) in this study. The addition of 0.2 vol.% of SSWs can already improve interface between matrix and SFs, reduce the microcracks in UHPC caused by shrinkage and initial load, increase SFs’ distribution and orientation with their high flexibility, thus enhancing the flexural toughness and resulting in the occurrence of multiple cracking flexural failure mode of UHPC with less than 2.0 vol.% SFs. The hybrid SWs and SFs reinforced UHPC possesses low electrical resistivity and can sense its initial cracking, residual flexural loading and cracking development by the measured fractional change in electrical resistivity. This is mainly coming from the inhibition effect of SWs on microcracks and the extensively conductive pathway formed by both SWs and SFs. The multiple cracking failure mode under flexural load and the self-sensing capacity to monitor crack initiation and propagation of UHPC with low content hybrid wires and fibers is important to develop multifunctional UHPC, thus providing a new approach for maintaining sustainable development of infrastructures.
Abstract
Stainless steel wires (SSWs) with micro diameter and stainless steel fiber (SFs) with millimeter diameter were incorporated together to develop multifunctional ultra-high [...]
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Study on Performance of Negative Temperature and High Strength Bed Mortar Material for Wind Power Engineering
L. Tongwei, Z. Jie, C. Guisheng, W. Linmao, Y. Maoqian

DBMC 2023.

Abstract
As the development process of affordable wind power projects accelerates, the height of tower hub shows a trend of development to 150m above. The technology of steel and concrete is widely applied. Bed mortar material, as the bonding material between precast concrete rings, is the key material to ensure the lifting speed of steel and concrete tower for wind power. In this study, the basic formula of negative temperature and high strength bed mortar material was explored, and its working performance and strength development under different curing conditions were further studied. The results show that the developed bed mortar material has excellent thixotropy and it is still operable at 50min. Under the condition of negative temperature curing, the early strength of bed mortar material is high, and the late strength develops well. Curing at ultra-low temperature of -15℃, the strength of -1d is 35.4MPa, and the strength of -7+21d is over 90MPa. In the outdoor natural curing environment of alternating positive and negative temperatures, the strength of 1d reaches 51.1MPa, the strength of 60d is 113.2MPa. The performance of bed mortar material far meets the requirements of the strength grade of 80MPa which is used in winter construction of wind power engineering.
Abstract
As the development process of affordable wind power projects accelerates, the height of tower hub shows a trend of development to 150m above. The technology of steel and concrete [...]
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Effect of Alkali-free Accelerator Containing Nano-silica on the Durability of Shotcrete
W. Liya, W. Kaiyu, C. Guisheng, Y. Maoqian, Y. Guangnuan

DBMC 2023.

Abstract
The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance tests and frost resistance tests. The results show that under the same conditions, the C30 shotcrete with nanosilica-containing alkali-free accelerator has a lower electrical flux and a greater impermeability rating than P10. The C30 shotcrete with nano-silica-containing alkali-free accelerator maintains a mass loss rate of about 0.4% after 200 freeze-thaw cycles, a 10.5% decrease in relative dynamic modulus of elasticity, a compressive strength loss rate of less than 20%, the bubble spacing coefficient and the average bubble diameter increased by 20.9% and 60.5% respectively, showing good frost resistance performance. This indicates that alkali-free accelerator containing nano-silica can improve the durability of shotcrete. In addition, a comparison was also made between ordinary accelerator shotcrete with nano-silica, and when 5% nano-silica was added, the properties of shotcrete were comparable to those of 2% nano-silica alkali-free accelerator shotcrete.
Abstract
The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance [...]
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Combining Wood Protection Options to Enhance Resistance against Decay and Improve Fire Safety of Engineered Wood Products like CLT
J. Van Acker, W. Li, X. Jiang, M. Durimel, L. De Ligne, B. Parakhonskiy, A. Skirtach, J. Van den Bulcke

DBMC 2023.

Abstract
Bio-based building products are considered key in our future socio-economic environment, since they are a very relevant nature-based solution (NbS) to climate change. The statement of President von der Leyen (European commission) to turn the construction sector into a carbon sink is critical in this respect: bio-based materials should be used on a larger and more targeted scale in the future. The long-term use of materials is therefore very important since we need to improve the lifespan of renewable materials to increase its carbon sink potential. Hence wood is increasingly considered as a main building material. Service life aspects are critical in relation to the EU Construction Products Regulation (CPR). Traditional treatments to protect against fungal decay and the impact of fire are not always performing adequately and often environmental impact has been an important consideration. The option to enhance wood properties using innovative technologies can be combined with better definition of the expectations and requirements. Besides focusing on combined innovative treatments of the wood matrix, also envelope treatments similar to the use of coatings can be envisaged. This all should lead to an increased use of timber and engineered wood products for green building. This paper mainly focusses on the increased use and high potential of CLT (Cross Laminated Timber) and options to use hardwoods and modified wood (like TMT) in relation to moisture dynamics to come to fit-for-purpose material properties even under more hazardous circumstances.
Abstract
Bio-based building products are considered key in our future socio-economic environment, since they are a very relevant nature-based solution (NbS) to climate change. The [...]
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Capacity of Wood as Flooring Material: Improvement of Thermal Performance of Wood/Phase Change Material Composites
W. Duk Suh, J. Nam, Y. Uk Kim, Y. Choi, S. Kim, S. Kim

DBMC 2023.

Abstract
Wood is a biomaterial with good carbon fixation capacity. Phase change materials (PCMs) can impart thermal storage performances to materials. The goal of this study is to improve thermal performance by impregnating PCM into porous wood. The chemical stability of the composites was analyzed to evaluate whether it was appropriate for PCM to be impregnated into wood. Thermal performance of the composites was evaluated through latent heat analysis and thermal conductivity analysis. As a result of the analysis, the composites showed improved thermal performance compared to pure wood. In addition, in order to evaluate the applicability of the composites for floor heating, the dynamic heat transfer test was conducted using specimens as flooring material. As a result, it was confirmed that room temperature maintained the indoor comfort temperature range for longer time in rooms where composite specimens were applied as floor material. Result suggests that the composites can reduce the time for operating heating energy for floor heating. Thus, composites produced in this study proved to have the potential to be used as floor finishing material for floor radiant heating systems.
Abstract
Wood is a biomaterial with good carbon fixation capacity. Phase change materials (PCMs) can impart thermal storage performances to materials. The goal of this study is to [...]
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Transforming low-quality sand into construction materials under 110℃ and Recycling of the Waste Solution
P. Qiu, Y. Sakai

DBMC 2023.

Abstract
A strong and eco-friendly material was transformed from low-quality sand via sol-gel method with ethanol as the solvent. 110oC was chosen as a target temperature because it is the average day temperature of the moon, which may be the first place for extraterrestrial development. The appropriate KOH content and ethanol concentration can improve the reaction degree and limit the side reaction. The main results indicated that the highest compressive strength (38 MPa) of the produced material could be obtained by using 20 mass% KOH and 90 V/V% ethanol. According to XRD and FTIR analysis, the formation of sanidine, zeolite, and tetraethoxysilane is the main reason for strength enhancement. Sanidine and zeolite could fill the gap between sand particles and tetraethoxysilane is a good consolidate. Excess ethanol in the waste solution can be reused with recycle rate above 65%. The total carbon emission is 197 kg CO2 eq/m2 after recycling waste solution, which is 35.82% of that produced by normal concrete. Therefore, a tough construction material can be synthesized from lowquality sand, which can partially substitute concrete. This material can address the shortage of raw materials for concrete and can be utilised for extra-terrestrial construction.
Abstract
A strong and eco-friendly material was transformed from low-quality sand via sol-gel method with ethanol as the solvent. 110oC was chosen as a target temperature because it [...]
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Recycling of Silty Waste Soil by CO2 Treatment for Construction Block Manufacture
Y. Du, Q. Zeng

DBMC 2023.

Abstract
The poor engineering performance of silty waste soil (SWS) seriously restricts its utilization in new constructions that, in turn, need a large amount of building materials. Meanwhile, traditional sintering technology of clay brick production is prohibited due to its high CO2 emissions. In the present work, a rapid CO2 mineralization method is proposed to treat SWS with active lime after the pressing forming process of building block manufacturing. The optimum mix proportion and pressing forming parameters of SWS blocks are presented. Microstructure of selected SWS block samples is characterized by mercury intrusion porosimetry (MIP) and X-ray computed tomography (XCT), and mineral changes are analyzed by X-rays diffraction (XRD). CO2 emissions from the SWS block production are evaluated considering the entire manufacturing process. Overall, the present study provides a proof-of-concept path that enables recycling of SWS for construction block production with low CO2 emissions.
Abstract
The poor engineering performance of silty waste soil (SWS) seriously restricts its utilization in new constructions that, in turn, need a large amount of building materials. [...]
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Partial Replacement of Fly Ash & Modified Bottom Ash as a Cement & Fine Aggregates in Concrete
P. R. Khare, D. P. Wanjari

DBMC 2023.

Abstract
This study envisaged the application of Bottom ash as a replacement of fine aggregate. In this study, bottom ash is thoroughly mixed with a PC-based High range superplasticizer ( HRSP) having solid content more than 60%, this sand is called as modified bottom ash (MBA are mixed at doses of 0%, 0.25%, 0.5%, 0.75%, and 1% by weight of bottom ash. This prepared bottom ash is referred to as modified bottom ash (MBA). MBA is substituted for fine aggregates in ordinary concrete in varying amounts from 0 to 50% by river sand and the concrete has been tested for Compressive strength, flexural strength, split tensile strength, and other durability characteristics it has been found that 10% MBA produce superior outcomes, the purpose of use was not achieved. Therefore, MBA has been increased up to 60% replacement with fine aggregates, the strength and durability properties achieved for concrete produced by 50% MBA with fine aggregate (sand) are compared to 100% fine aggregate (sand) concrete and has observed similar results due to addition of HRSP. In the end, it can be concluded that High Range Superplasticizer HRSP is quite efficient for replacing Bottom ash with fine particles.
Abstract
This study envisaged the application of Bottom ash as a replacement of fine aggregate. In this study, bottom ash is thoroughly mixed with a PC-based High range superplasticizer [...]
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Durable Textile-reinforced Concrete Made of Fast-setting, Mineralimpregnated Carbon-fibers (MCF) Reinforcements and Alkaline-activated Matrix
J. Zhao, A. Ameer Hamza, M. Liebscher, A. Bartsch, E. Ivaniuk, M. Butler, V. Mechtcherine

DBMC 2023.

Abstract
Textile Reinforced Concrete (TRC) is a class of material with massive potential to strengthen existing or build entirely new thin-walled structures. However, state-of-the-art polymer-based textile reinforcements commonly suffer under weak compatibility with concrete and insufficient reinforcing efficiency at elevated temperatures. Mineral-impregnated carbon-fiber (MCF) composites represent instead a promising alternative reinforcement with a wide-ranging innovation potential regarding digital and automated processability, freedom design, chemical compatibility and ecological and environmental footprints. Among the existing variants of mineral impregnation, geopolymer (GP) impregnation for carbon fiber (CF) enables stable early-age rheological properties and fast-setting by moderate-temperature activation. The paper at hand presents a methodology to automatically manufacture textile reinforcements made of MCF composites via a continuous pultrusion and robotic–assisted structuring process to meet future market demands. After an advanced geopolymerisation process by thermal curing, the resulting gridlike reinforcements were implemented in a fine-grained, alkali-activated material (AAM) based concrete matrix and characterized with respect to their uniaxial tensile performance. By further applying AAM as cement-free binder, sustainable and fireproof reinforced concrete can be designed with an evident reduction in CO2 emission as compared to conventional cementitious systems. The improved chemical affinity facilitated by GP impregnation governs the cracking phase, resulting in a finer and more diffuse pattern, whereas the higher unidirectional strength of epoxy (EP)-impregnated yarns is responsible for the higher ultimate strength of the composite.
Abstract
Textile Reinforced Concrete (TRC) is a class of material with massive potential to strengthen existing or build entirely new thin-walled structures. However, state-of-the-art [...]
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Durable Structural Concrete Using Fine and Coarse Recycled Aggregates (Type A and Type B)
C. Vintimilla, M. Etxeberria

DBMC 2023.

Abstract
The use of Recycled concrete aggregate (RCA, type A) and mixed recycled aggregate (MRA, type B) is an alternative for structural concrete production to reduce natural resource exploitation and landfilling of construction waste. However, the lower quality of recycled aggregate compared to that of natural aggregate, and consequently the lower durability of recycled concrete, make it necessary to limit the percentage of replacement of raw aggregates by recycled aggregates. The objective of this study is to analyse the adequacy of using different percentages (following European standards) of coarse and fine type A and type B recycled aggregates for structural concrete production. All the concrete mixtures were produced using 300kg/m3 of cement and an effective water: cement ratio of 0.48 to be exposed to the XC1-XC4 environment. In addition, the conventional concrete (0% recycled aggregates) was also produced using an effective water: cement ratio of 0.52. The physical and mechanical properties, drying shrinkage values, and durability property of sorptivity and water penetration values were determined in all the produced concretes. It was concluded that the concrete produced with up to 60 % coarse RCA and 30 % fine RCA (type A) aggregates achieved adequate properties for structural concrete. In addition, the use of MRA mixed recycled aggregate (type B) was also possible for structural concrete production when it was employed in the replacement of natural aggregates up to 40% for coarse MRA and 15% for fine MRA simultaneously.
Abstract
The use of Recycled concrete aggregate (RCA, type A) and mixed recycled aggregate (MRA, type B) is an alternative for structural concrete production to reduce natural resource [...]
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Carbon Neutral Concrete – Challenges and Solutions for Sustainable Future
M. Plançon, Z. Shu Qiang, J. Wong

DBMC 2023.

Abstract
As the climatic impact is becoming a more important topic for most of the nations which signed the COP 26 accords; many concrete and cement companies have announced their carbon reduction ambitions. Although the CO2 reduction pace varies from one country / company to the other, many of them have clearly stated their commitment towards concrete carbon neutrality in 2050. As a result, we can observe the accelerated emergence of a multitude of new technologies targeting the reduction of carbon content in concrete. The presentation proposed will go over the consequences for the concrete industry of this construction industry’s endeavor climatic impact reduction. It will explain some of the main challenges paving the cement and concrete industry’s journey towards carbon neutrality. It will deep dive in the principles and impacts of the most recent and advanced regulations in terms of low carbon construction such as, for example, RE2020 in France. It will also illustrate some of the realistic solutions currently implemented to reduce the carbon footprint of concrete and cement and adapt to this new market environment, including the use of the latest loT technology which allows the concrete producer to improve their material management, operational efficiency as well as the commercial leverage. In a world where raw materials scarcity becomes increasingly stringent, it will also explore the solutions for the concrete industry to promote circular economy. Finally, it will describe the most probable paths towards carbon neutral concrete and how they will inevitably include environmental footprint reduction beyond climatic impact.
Abstract
As the climatic impact is becoming a more important topic for most of the nations which signed the COP 26 accords; many concrete and cement companies have announced their [...]
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Li, Kefei 20
Tsinghua University China /...

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