Scipedia: Documents published in 2020

Influence of High Volume Fly Ash and Recycled Aggregates in Chloride and Carbonation Resistance of Concrete

Scipedia content — Wed, 23 Sep 2020 15:38:27 +0200

This paper deals with the evaluation of the influence of recycled concrete aggregate (RCA) and the employment of high volume of fly ash (FA) on the physical, mechanical and durability (chloride ion penetration and carbonation) properties of concretes. The obtained values of which, being compared to those of conventional concretes. Concrete was produced using 0%, 25% and 50% FA in replacement of Portland cement, and 0% and 50% of RCA in substitution of natural aggregates. All the concretes were produced employing an effective water-cement ratio of 0.50. The physical properties at 28 days and the compressive strength at 7, 28 and 90 days were determined in all the concretes produced as well as the assessment of durability (penetration of chlorides and depth of carbonation) on all concrete mixtures. The depth of the carbonation was determined after submitting every concrete sample to a series of accelerated tests at 20% of CO2 concentration during 7, 14 and 28 days after the curing period in the humidity room and pre-condition in the laboratory. The chloride penetration was determined at 28 and 90 days of curing. It was concluded that the employment of 50% of un-carbonated RCA increased the early strength of concrete produced using FA, and at late ages, RCA concretes achieved similar strength when 25% of FA was employed. The concrete produced with 50% of FA achieved the highest resistance to chloride ion penetration also when RCA was employed. Although the use of FA increased the carbonation depth of the concrete samples, the employment of the un-carbonated RCA reduced that effect. The employment of RCA with CEM II or binder with 25% of FA caused the lowest carbonation depth.

Decision Support to Identification of Road Infrastructure Segments With Poor Conditions

Scipedia content — Wed, 23 Sep 2020 15:38:20 +0200

Planning of maintenance activities (an integral approach) on ever growing system such as urban road infrastructure requires decision makers to take into account large number of different data and usually conflicted criteria, derived from several aspects of analysed problem. This systematic approach to planning is based on the main three steps: identification of alternatives, their validation and selection for inclusion into a maintenance plan. Most of authors are dealing with the last two steps however, focus of this research is on the first step. This step is a critical phase of planning because it is important to identify road infrastructure segments that need to be improved. Meaning, those with poor condition. The condition of a segment must be expressed as simple as possible (by unique Condition Assessment Value) and by usage of few but most relevant criteria (such as level of service, safety, time period passed form the last renovation and stability). Another important issue is provision of relevant, relatively quick and consistent expert assessment of segment condition according to above mentioned criteria and for large number of segment. To insure such assessment with high quality of segments identification this paper propose an decision support concept/expert system based on combination of trained and tested Artificial Neural Networks (ANN) and Simple Additive Weighting (SAW) method. The concept is validated on urban road infrastructure of city centre of Split, Croatia and it proved to be useful for determining a set of road infrastructure segments where maintenance activities should be undertaken.

Are Mineral Toppings of Asphalt Roofing Sufficient to Protect Flat Roofs and Roofing Felt Alone?

Scipedia content — Wed, 23 Sep 2020 15:38:13 +0200

Mineral surfaces are an integral part of bituminous roofing felt. Their task is to protect less resistant elements from the destructive effects of the environment. Since the first application in 1897, they have been constantly improved in the direction of better functionality and aesthetics. It often turns out that the intended effect has not been achieved. During the first years of operation, there are signs of roof damages on most facilities. Due to the complex interaction of roofing elements, several causes of damages can be defined. A group of processes taking place in mineral roofing toppings is important for roofing felt. Mineral surfaces are exposed to physical, chemical and biological factors. They cause losses due to the unavoidable breaking of adhesion to the modified asphalt. Pulling out caused by factors occurring on the roof is a long-term process with more effects on the covering, in particular its durability and tightness. In the paper, the reasons for the release of mineral topping from the SBS modified asphalt layer were defined. The analysis shows that as a result of significant degradation and harmful impact of mineral coverage, this layer may lose the ability to protect the roofing paper, and long-term changes threaten the durability of roofing materials. Solutions have been proposed to significantly reduce the phenomenon caused by specific factors.

The Durability of Plant-Based Air Filtering Systems in Buildings: From an Air Quality and Energy Reduction Perspective

Scipedia content — Wed, 23 Sep 2020 15:38:06 +0200

After the oil crisis, all the commercial and residential buildings were designed with tightly sealed envelopes to minimize the air leakage through the building to save energy. Since buildings were no longer able to breathe naturally, indoor air quality problems started to occur. Currently, there is still a dilemma between these two parameters inside the buildings. To address IAQ issues and reduce the energy loads in mechanical conditioning systems, the plant-based air filtering system is designed. The proposed system is a hydroponic system (plants growing without soil) that is composed of a mixed bed of activated carbon adsorbents and porous glass stones that capture and filter the toxins in the air. HVAC‐integrated plant walls that include growth media are designed to support the plants and capturing toxins. These toxins are then metabolized by the plants which can create a self‐regenerating filtration system that requires less outdoor air being fed into the building, thereby reducing the conditioning costs associated with HVAC. This paper is focused on the durability of the design and fabrication of a plant-based air filtering system from an air quality and energy reduction perspective.

Application of Soft Computing Methods to Increase Sustainability in Construction

Scipedia content — Wed, 23 Sep 2020 15:37:59 +0200

In the last three decades the soft computing methods were used by the research community in almost every branch of construction, providing successful and convenient solutions for different problems in civil engineering. This paper presents some of the applications of these methods - especially neural networks (NN) and support vector machine (SVM) - in sustainable construction, i.e. its economic, social and environmental aspects. Soft computing applications were made in the last several years by our research team at the Faculty of Civil Engineering in Skopje, N. Macedonia, in collaboration with other authors from our and other countries. Several predictive models were developed using: general regression neural network (GRNN), support vector machine (SVM) and radial basis function neural network (RBF NN), using predictive modelling software DTREG. Applications of these models cover most of the aspects of sustainability in construction. Models were focused on predicting: road structure construction costs, bidding price in construction, sustainability assessment at early facilities design phase, predicting construction cost and construction time and predicting consumption of energy in buildings. Some of the mentioned developed predictive models are hybrid, composed of process-based and data driven models which contributed very much to the improvement of the accuracy of the predicting. The general conclusion is that the soft computing methods are a useful tool for developing models in the area of all aspects of sustainability and their application can lead to increasing sustainability in construction.

Effects of Long-Term UV Exposure on the Performance of Cement Plasters Integrated with Thermochromic Paint and PCMs for Building Facade Applications

Scipedia content — Wed, 23 Sep 2020 15:37:52 +0200

The exterior finish layer in building facades is exposed to considerable environmental loads, which can reduce the service life of the materials, increasing the need for replacement. New climate challenges impose to look more carefully at the long-term performance and durability of building components and materials. Thermal stresses due to daily temperature fluctuations and UV exposure can significantly damage facades and degrade their performance. This research measures the long-term performance of a responsive cementitious finish plaster. The developed cement plaster is combined with phase change materials (PCMs), and thermochromic (TC) pigments to control solar radiation and surface temperatures dynamically on the exterior façade year around. The main objective of the study is to quantify the effect of long-term UV exposure on the optical performance of the cement plasters. PCMs with three different melting temperatures of 18oC, 24oC, and 28oC were combined with two different colors of blue and red TC paint with a transition temperature of 31oC. Accelerated UV aging of the samples was performed using lab tests to simulate exposure to UV radiation for two years. The solar reflectance of the samples was characterized before and after the accelerated UV aging tests. The results of the aging tests revealed that UV exposure impacts the solar reflectance of the finish material based on the method of integrating the TC paint to the cement plaster. In the case of TC paint applied to the surface, the solar reflectance of the plasters with only the TC is reduced by 15% after aging, while the ones combined with PCMs have a similar solar reflectance value after aging.

Rainwater Management of Ventilated Facades: Impact of Joint Width and Cavity Size

Scipedia content — Wed, 23 Sep 2020 15:37:44 +0200

During a rain event, most of the raindrops reaching the facade either splash back or run off the exterior surface of the facade. However, it is evident that also a portion of the water infiltrates through the open joints of a ventilated facade. The infiltrated water may either be drained in the cavity to the bottom of the wall or reach the insulation layer. If there are any deficiencies present in the insulation layer or at the connection of the brackets, the infiltrated water might introduce problems. Additionally, if the cavity is not able to drain all the infiltrated water or adhered droplets to one of the cavity surfaces do not dry out, moisture problems might occur. Experiments were conducted to determine the infiltration rate through ventilated facades with open joint widths of 5 mm, 10 mm and 15 mm and cavity widths ranging from 190 mm to 40 mm. It was observed that the amount of infiltrating water was larger for larger joints widths. Due to the larger kinetic energy of the drops flowing through the larger joint widths, the drops were able to reach the exterior surface of the insulation layer, even for large cavity widths. The results from the experimental assessment were used as input parameters for hygrothermal simulations to determine the risk of moisture problems.

Implication of Microbial Biofilm in the Biodeterioration of Cementitious Materials in the specific context of Anaerobic Digestion Conditions

Scipedia content — Wed, 23 Sep 2020 15:37:37 +0200

Anaerobic digestion is a renewable energy production process based on the fermentation of biodegradable biomass. The industrial digesters are usually made of cementitious materials. However, the microbial production of several aggressive compounds (CO2, NH4 + and volatile fatty acids) during the digestion leads to the deterioration of the concrete structure. The growth of microbial biofilm on the surface of concrete is suspected to generate an even more severe biodeterioration. The goal of this study is to provide a better understanding of the biofilm involvement in the biodeterioration of cementitious materials during an anaerobic digestion process. More precisely, this study is focused on the biofilm heterogeneity and its development on cementitious materials in anaerobic digestion. Lab scale anaerobic bioreactors mimicking industrial anaerobic digestion medium were carried out to immerge CEM I cement pastes in this medium during 2, 3, 4 and 5 weeks. The deterioration of cement pastes was evaluated by using a scanning electron microscope to determine the deteriorated thickness and to quantify the volatile fatty acids in the medium. Biofilm attached on the surface of cement pastes was analyzed through molecular biology techniques, such as 16s rRNA gene sequencing analysis and qPCR.To assess the biofilm heterogeneity, successive stalls of the layers of the biofilm were realized using physical biofilm removal techniques. Three microbial fractions are defined: the planktonic microorganisms, the lousy attached and the strongly attached ones. Results showed that the methanogenic Archaea are found mainly in the medium while around half of the microbial population strongly attached is made of acidogenic bacteria. These results suggest that the biofilm could increase the biodétérioration of concrete since the fatty acids are massively produced at the proximity of the surface of the cementitious samples.

Effect of Vapor Diffusion Port on Drying of Wood-Frame Walls

Scipedia content — Wed, 23 Sep 2020 15:37:29 +0200

Vapor diffusion ports (VDP) that are drilled in the exterior sheathing of wood-frame walls are commonly used in wood-frame construction in the coastal region of British Columbia with the intention to improve the drying capacity of wood-frame exterior walls. This practice was originated following the systematic building envelope failures due to rain penetration that occurred in this region around 1985-1995. A previous laboratory study carried out by FPInnovations found that the diffusion ports provided substantial improvement in the drying rates of Oriented Strand Board (OSB) sheathed walls, but not for plywood sheathed walls (Hazleden and Morris, 2001). A more recent laboratory test (Wang, 2018) using wood-frame walls with higher insulation levels in compliance with the current more stringent energy code found that VDPs did not significantly improve the drying rates; On the other hand, the provision of VDPs may allow moisture ingress into the wall assembly instead in a damp environment. The difference in these two studies in terms of test wall sizes, moisture sources, and test conditions may have attributed to the different findings. To provide a more comprehensive and systematic evaluation of the effect of VDPs, hygrothermal simulations using Wufi-2D are carried out in this study. The Wufi-2D model is firstly validated by comparing simulation results to the test results provided by Wang (2018), which tested the effect of VDPs under laboratory conditions by using a wetted wood block installed inside each wall assembly as a simulated moisture source. The simulation results agree well with the measurements. The Model is then used for sensitivity analysis with different levels of rain leakage with and without VDPs using yearly weather data. The variables included are types of exterior insulation, types of sheathing (OSB versus Plywood), and types of sheathing membrane. This paper presents the validation of the model and simulation results under transient conditions with rain leakage. General conclusions on the effect of VDPs are provided

Examination of Optimum Construction Area for Appropriate Thickness in Polyurethane Waterproofing Construction

Scipedia content — Wed, 23 Sep 2020 15:37:18 +0200

Polyurethane waterproofing membranes are constructed at building sites by applying liquid material to substrate. The membrane thickness is related to the durability of the waterproof material, so quality control during construction is important. However, the membrane thickness is likely to be unstable because it is affected by various factors, such as the environment, substrate conditions, method of waterproofing material application, and construction skills. Therefore, a reduction in thickness variation is extremely important to secure the quality of the waterproofing membrane. To examine which construction conditions can ensure a uniform and appropriate thickness, we examined the combination of allocation method of the suitable construction area and application tools as an example of process control during construction. The construction area width and length were important, and a comparatively uniform and appropriate thickness could be ensured, when construction was carried out over an area with a 1.4-m width and length of 5.15 m by using the trowel and squeegee.

Durability of Mortars Packaged with Production Waste of Autoclaved Aerated Concrete

Scipedia content — Wed, 23 Sep 2020 15:37:10 +0200

The building sector is responsible for the introduction of about 40% of the waste in the environment (60 Mtons per year in Italy), with serious consequences for our future. Therefore, the statistics of the last few years have induced many researchers and many companies to investigate more sustainable products and technologies. Among these strategies, the re-use of waste materials has been widely encouraged. Many solutions have been proposed in the field of mortars for which the use of waste products such as ceramic materials, polystyrene, clay, concrete, has been tried out. The results have often been encouraging, especially for masonry mortars. Nevertheless, very few attempts have been made to place this type of products on the market. Moreover, the "younger" building materials such as Autoclaved Aerated Concrete have not been fully investigated in their potential use as recycled aggregates. The goal of this research was to evaluate the characteristics of mortars packaged with different percentages of production waste of Autoclaved Aerated Concrete components as aggregates, in order to assess the possible use of these conglomerates as masonry mortars or as plasters. The first campaign included tests for determining mechanical resistance, density, capillary water absorption, adherence to substrate, resistance to carbonation. The tested mortars had satisfactory mechanical characteristics and generally exhibited a good capacity to withstand the actions of atmospheric agents. Finally, the results highlighted the direct connection between Autoclaved Aerated Concrete percentage and mechanical and durability properties.

Preconditioning of Specimens - Drying Influence on Alkali-Activated and Geopolymer Mortar

Scipedia content — Wed, 23 Sep 2020 15:15:56 +0200

Alkali-activated materials (AAM) are now seriously considered by the cement industry as an economical alternative to Portland cement, especially for its low CO2 footprint. However, their durability still remain to be assessed in more details. The aim of this study is to focus on the sample preconditioning conditions required for testing, especially the drying stage involved in most of the current tests. Four alkali-activated binders were studied: a geopolymer (Na-silicate activated metakaolin), a Na-carbonate activated slag (GGBS), a Na-silicate activated slag and a Na-silicate activated mixture of 50% metakaolin with 50% GGBS. After an endogenous cure of 28 days at 20°C, mortar specimens were dried at different temperatures (from 20°C to 125°C) until mass stabilization. Drying kinetics and released water contents were evaluated, as well as physical, mechanical and mineralogical analyses at the end of drying. Optimal drying temperature for each alkali-activated binder was determined by coupling mechanical strength measurements and mercury intrusion porosimetry. This study revealed that an inappropriate drying temperature could modify the porosity of some classes of AAM, and reduced the compressive strength by up to 30 to 40%. Antagonistic behaviors were observed in the four alkali-activated materials studied, therefore one should be careful about selecting preconditioning protocols for assessing the properties and the durability of these binders.

Characteristics of the Changes in the Compressive and Tensile Stress of the Construction Sealant under Cyclic Movement

Scipedia content — Wed, 23 Sep 2020 15:15:49 +0200

A compact fatigue testing machine to quantitatively evaluate the effects of this complex degradation of sealants and the load change of the sealant under dynamic fatigue has been developed. The developed fatigue testing machine is compact with dimensions of (width) 100 × (length) 135 × (height) 110 mm. It can be installed in an outdoor exposure test site or in a chamber. Thus, this machine can be used for performing various compounded accelerated degradation tests. We report the use of this testing machine to examine the effects of this complex degradation of sealants and the load change of the sealant under dynamic fatigue.

Effect of Coexisting Materials on Secondary Ettringite Formation

Scipedia content — Wed, 23 Sep 2020 15:15:41 +0200

The expansion of cement paste can occur as a result of secondary ettringite formation due to attack by sulfates. It has been proposed that this expansion is affected by coexisting hydration products such as calcium-silicate-hydrates (C-S-H), although the mechanism has not yet been clarified. The present study experimentally examined the effects of coexisting materials on secondary ettringite formation. Synthesized monosulfate and coexisting materials such as C-S-H were mixed with a sodium sulfate solution. The secondary ettringite proportion was markedly increased by the presence of C-S-H, and calcium-aluminate-silicate-hydrates (C-A-S-H) containing four-coordinate Al were formed in these samples. It is evident that ettringite is likely to form from four-coordinate Al, and that C-S-H promotes secondary ettringite formation because it transitions six-coordinate Al derived from the monosulfate to four-coordinate Al by substituting Al in the Si chains.

The Palace of Westminster Courtyards Project: Sourcing Stone for Repair and Conservation

Scipedia content — Wed, 23 Sep 2020 15:15:35 +0200

The Palace of Westminster, commonly known as the Houses of Parliament, serves as the meeting place of the House of Commons and the House of Lords and is situated on the north bank of the River Thames in London, England. The site is part of the UNESCO Westminster World Heritage Site. The building was constructed of magnesian limestone, selected following a nationwide survey of building stones carried out by a Government Select Committee. However, some of this stone began to decay soon after construction in the mid 1800s. As the majority of the stonework has survived very well the aim of the work was to source a demonstrably durable material with characteristics which align with the majority of the existing stonework. Samples were taken from the building for petrographic analysis in order to identify compatible material in quarries, either working or which could be re-opened. Durability of the magnesian limestone was assessed using both accepted tests and novel methodology. Large scale walls were constructed in the laboratory and exposed to accelerated frost weathering with realistic temperature parameters. The logistical problems with sourcing the original building material, the nature of the transport and the masons‘ unfamiliarity with the stone may all have played a part in undermining its durability. When magnesian limestone is properly selected and used correctly, its reputation for being of poor durability is largely unfounded. Suitable sources for replacement stone were located which provided several options for both immediate and long-term sourcing for repair and conservation.

Hydronium Detection in Hardened Concrete

Scipedia content — Wed, 23 Sep 2020 15:15:27 +0200

The monitoring of reinforced concrete structures allows us to detect the presence of aggressive agents into of the concrete matrix, on site and in a real time. These aggressive agents can produce the unexpected failure of the structures, thus discovering their presence is a fundamental aspect in the preservation of people safety and the durability of the structure. On the other hand, helps to reduce the cost of maintenance and repair operations, due to allow us to identify the problems faster, minimizing the intervention to be done. The present research paper was focused in the hydronium detection; the reduction of this species generates hydrogen, the hydrogen produces the embrittlement and cracking of the steel, which seriously compromises the right behaviour of the structure. The problem of hydrogen appears in industries such as ammonia processing or petrochemistry industries and nuclear power plants. All of them are industries in which a failure seriously compromises the welfare of people and the environment. Therefore, the detection of hydrogen penetration in reinforcement concrete structures in these cases are very interesting. In this study, with the purpose to detect the hydronium or hydrogen in the hardened concrete matrices is proposed the use of voltammetric sensor, which is part of a multisensory system called Electronic-Tongue. This is a preliminary study. The objective of these initial steps was to evaluate the detection capability of the sensor. Currently, have been designing a sequential test in order to evaluate the sensor in different partial hydrogen pressures with the purpose to develop mathematical models to the hydronium or hydrogen detection and quantification in hardened concrete matrix.

Neural Model of Projecting Compressive Strength of Cement Concrete Intended for Airfield Pavements

Scipedia content — Wed, 23 Sep 2020 15:14:08 +0200

This work present to the mathematical model in the form of ANN, intended for projecting concrete compressive strength. Input data was classified according to the type of component material and its content in concrete mix (cement contents, coarse aggregate, fine aggregate, water and admixtures). In order to determine mathematical model, a multilayer, one-way perceptron network was used, recursion network with sigmoidal neurons. The model assumes that neurons are gathered in some layers (one input layer, hidden layers and one output layer). The conducted cross-section of the influence of variables parameters values (learning constant - α and momentum values - η) on the accuracy of representation of compressive strength was analyses. Assessment criterion was assumed taking into consideration the lowest mistake level and 100% compliance. According to the obtained analysis results ANN was assumed the best representing network for constant value of momentum 0,3, learning constant of 0,05 and 6 neurons in a hidden layer. Very good coincidence of component models with experiment results was achieved. At testing stage, the coincidence was achieved at the level of 99.74%, in case of the assumed network structure. During model verification by means of experimental results, the average coincidence was 99.83%.

Selecting Criteria for Assessing “Environmentally-Friendly” Material Options in Construction: Part II

Scipedia content — Tue, 22 Sep 2020 17:45:21 +0200

One of the design team’s tasks is assuring that their project has a low negative impact on the environment. This comes from regulations as well as expectations of direct benefits (reduction of operating cost, the project’s improved image in the eyes of the public, etc.). To fulfill this task, one needs to define criteria for assessing the design options. These are to correspond to the individual qualities of the project, and they should be significant and possible to assess. The paper, divided into two parts, presents a review of the literature concerning the criteria for the assessment of design solutions defined as "green" or “environmentally friendly”. Part I presented the method of the analysis and investigates into the number and type of criteria adopted in the sample of papers being the object of analysis. This part focuses on the ways of defining criteria values, weights, and methods of multicriteria assessment.

Fundamental Properties and Durability of Concrete with Gasification Molten Slag as Fine Aggregate

Scipedia content — Tue, 22 Sep 2020 17:45:14 +0200

The proportion of electricity generated by coal-fired thermal power plants has been rising in Japan as a result of the nuclear plant accident caused by the Great East Japan Earthquake of 2011. Coal-fired electricity generation has a large environment impact, so the commercial application of integrated coal gasification combined cycle (IGCC) has been promoted. IGCC is an efficient generating method combining a steam turbine and a gas turbine. However, IGCC plants generate coal gasification molten slag (CGMS) and it is necessary to establish effective utilization methods for this slag for further promotion of IGCC technology. In this paper, the fresh properties, hardened properties and durability of concrete containing CGMS as fine aggregate are investigated. The results show that, in comparison with concrete using conventional fine aggregate, the air content introduced by an air-entraining agent is lower and bleeding is increased when CGMS is used as a fine aggregate. As for the hardened properties, compressive strength is slightly lower, while freeze-thaw resistance is significantly reduced. In additional tests, it is found possible to improve freeze-thaw resistance by increasing the air content

Influence of Grid Presence in the Characteristics of Applied Mortars

Scipedia content — Tue, 22 Sep 2020 17:45:08 +0200

The most commonly used wall coverings are still, undoubtedly, plasters and renders, whether lime-based or cement-based, whether traditional and prepared in-situ or pre-dosed. In accordance with the available standards, the characterization of these mortars is made on laboratory test specimens, with dimensions, curing conditions and test procedures according to the prescribed. However, when applying these mortars to the real substrates, their behaviour will not be the same. After application of the mortar to the substrate, an interface will be formed, and the interactions that occur after the contact of the mortar, still in the plastic state, with the substrate will change over time due to the hydration kinetics and absorption of the substrate. It is very important to know the real behaviour of mortars after application, in order to ensure their durability. A research project is being developed to analyse the proper behaviour of mortars after application to the substrates. In order to characterize a mortar after application to a substrate, it is necessary to detach it. The introduction of a fiberglass grid in the mortarsubstrate interface makes the detachment easier. The purpose of this study is to determine if the placement of this grid will influence the characteristics of the applied mortar. For this, an experimental campaign was carried out, comparing the characteristics of two mortar formulations, applied to different types of substrate (without introduction of the fiberglass grid), with the characteristics of these mortars applied to the same substrates, but with the introduction of a fiberglass grid at the interface mortar-substrate. In this paper, we present the results obtained for some of the physical and mechanical characteristics of cement and hydraulic lime mortars.

Verification of Building Constructions Surroundings Based on Airborne Laser Scanning Data

Scipedia content — Tue, 22 Sep 2020 17:45:01 +0200

Light Detection and Ranging, as an active Remote Sensing Technology, enables gathering accurate, three-dimensional point cloud of scanned objects. Laser scanning might be provided on the terrestrial level for specific, defined constructions, as well as on the airborne level for aerial or linear objects. Using a laser sensor mounted on a moving platform is currently the most efficient way of obtaining in a short period, accurate positions of billions of points as a representation of a scanned area. Based on this kind of dataset it is possible to perform three-dimensional analysis of the safety of scanned objects without additional measurements in the field. This article presents the analysis performed in vMatic software on data from Airborne Laser Scanning for medium voltage power line verification of obstacles with the buildings. The analysis took less than 20 seconds for the detection of buildings points that are closer than 5m from conductors for seven spans wit a total length of almost 400m. Providing distance verification on 3D point cloud data is the fastest way to obtain a hazard awareness in a short time. Once acquired by LiDAR data can be used for other various analyses for any construction, depending on current, expected and future needs.

Morphology Changes and Fillers migration in Urethane Composites during Thermal Degradation.

Scipedia content — Tue, 22 Sep 2020 17:44:54 +0200

Polyurethane composite coatings are frequently applied to strengthen the barrier properties of various construction materials such as wood, metal and concrete. The changes of color and glossiness of the composite coatings for building materials proceeds more slowly than that of polyurethane because of containing fillers and several types of additives. However, the most critical barrier properties have not been studied directly based on the difference from the degradation mechanism of polyurethane coatings. Additionally, the difference in thermal and UV degradation mechanisms of coatings is not clear in the existing studies dealing with conventional accelerated weathering tests and outdoor exposure tests. Therefore, the behavior of the filler contained in the coatings was observed using an oven to accelerate thermal degradation. The chemical analysis of the coating surface by XPS and the analysis of the images and elemental mappings by SEM-EDS were carried out, and the mechanism of degradation progress was investigated. In addition, the temperature dependency of the degradation was studied in changing the heating temperature. It was suggested that polymer and fillers interact in promoting mass transfer at the same time as the thermal degradation reaction consequently.

Measurement of Moisture Content and Volume Change Distribution Inside Cement Paste Specimens Using X-Ray CT Imaging

Scipedia content — Tue, 22 Sep 2020 17:44:47 +0200

The purpose of this study was to clarify the internal change of concrete structures during drying. Therefore, we used X-ray CT to investigate water content and volume changes inside cement paste specimens during drying. Changes in the CT image intensities and measurements on the images indicated water content and volume changes, including local changes detected with digital volume correlation. Next steps will be to understand the link between volume changes and the local water content.

Assessment of Moisture Performance of National Building Code Canada Compliant Wall Assemblies under Climate Change

Scipedia content — Tue, 22 Sep 2020 17:44:41 +0200

Due to climate change, higher temperatures and rainfalls are expected to happen in some areas of Canada, which might increase the climate loads on buildings and lead to premature degradation of moisture-sensitive materials in wall assemblies. To investigate potential durability issues in three cities across Canada (Ottawa, Vancouver and Calgary), code-compliant wood-frame walls with two types of claddings, stucco and brick, were simulated using Delphin 5.9. Two different climate data sets, historical and future when a global warming of 3.5ºC is expected to be reached were used. The hygrothermal performance in terms of mold growth risk was analysed with respect to cladding types, considering air leakage. All the three cities are similarly warmer in the future. However, wind-driven rain (WDR) is higher in Vancouver than in Ottawa and Calgary. With brick cladding the relative humidity is kept below the threshold for mould development only in Ottawa and Calgary. With stucco in future, while Ottawa shows greater mould indices than historical, Calgary shows opposite behavior. The results suggest that the risk of mould growth due to air leakage may decrease in the future.

Validation of Three Methods of Selecting Moisture Reference Years for Hygrothermal Simulations

Scipedia content — Tue, 22 Sep 2020 17:44:33 +0200

Hygrothermal simulations are necessary to permit analyzing moisture performance when designing building envelopes. Owing to the high computing time and cost of the long term simulations, a common approach is to select representative year(s), the Moisture Reference Year(s), from a longterm series of climate data. It is assumed that the use of Moisture Reference Year(s) (MRYs) provides equivalent results as those provided using long-term series. The selection of MRY(s) is by itself based on the one of the methods available in the literature. In the present study, three methods of selecting the MRYs were evaluated i.e. the moisture index (MI), severity index (Isev) and climatic index (CI). Simulations were performed using individual years of historical climate data extending from 1986 to 2016 and projected future climate data representing the scenario with a 3.5°C increase in average temperature which is expected to occur from 2062 to 2092. Brick cladding installed on a wood frame wall assembly subjected to the climate of three different Canadian cities was selected for analysis. The cities selected were Vancouver (BC), Calgary (AB) and Ottawa (ON). These cities have differing levels of moisture loads. The year having the mould index value more than 3 for highest number of hours among the individual years was compared with the MRY given by three selected methods. A method was considered to be accurate in terms of the prediction if the year selected by that method gives the number of hours with mould index more than 3 which lies in the same class as that of year having maximum corresponding value. In general, it was observed that none of the methods provides the worst year with 100% accuracy, however for most of the cases, Isev method performs better than other two methods in terms of MRY selection.

Study on a Proper Repair Cycle of Finishing Materials in Condominiums

Scipedia content — Tue, 22 Sep 2020 17:44:24 +0200

In this paper, we discussed the concept for appropriate repair period for finishing materials of reinforced concrete structures. We investigated the actual building repair cycle, the progress of carbonation of concrete, and the adhesion strength of various finishing coating. In addition, we carried out 10-years exposure test of concrete with various finishing to evaluate the progress of carbonation and the degree of deterioration of the finish coating material. From these results, we showed the possibility of extending beyond the current repair cycle.

Performance and Durability of Adhesive Tapes for Building Applications. From Product Documentation to Scientific Knowledge (and Back Again)

Scipedia content — Tue, 22 Sep 2020 17:44:17 +0200

Adhesive tapes are used extensively in both new buildings and renovation projects in order to achieve airtight building envelopes and energy efficient buildings. It is important to be able to reliably predict whether these adhesive solutions are durable. In our roles as both a research institute and a national approval body for building materials, SINTEF have been performing product evaluations and testing of adhesive tapes for 10 years. During this time, we have tested the durability of more than 30 different tapes on a variety of substrates commonly used in the building industry. After systemising and analysing this data, we have gained valuable insight into the factors governing the durability of adhesive tapes for the construction market. In this paper we share our findings and discuss how we intend to utilise the new knowledge in the design of further scientific experiments in the field.

Seismic Performance of RC Moment Frame Structures Made with EAF Slag Aggregates

Scipedia content — Tue, 22 Sep 2020 17:44:11 +0200

Sustainability in the construction industry is becoming everyday more a major issue in todays world. To accomplish sustainability goals, adopted also by the Agenda 2030 of the United Nations, wide research has been carried out in the past years. Among this, the use of recycled aggregates has been proven to be promising both in terms of sustainability and material properties. Electric Arc Furnace (EAF) concrete has demonstrated a significant increase in mechanical properties when compared to natural aggregates (NA) ones. However, the mechanical properties enhancement is accompanied by an increase of its specific weight and the overall effects of its use in RC structures subjected to dynamic loads, has not been investigated yet. The present study aims to investigate the seismic reliability of reinforced concrete frame buildings made with EAF in comparison to the same structural configurations made with NA concrete, considering three different configurations (3-, 6- and 9- story building type) designed considering ordinary concretes made with natural aggregates.

Effects of Finishing Materials against Carbonation and Corrosion Condition of Model Building Exposed to Outdoor Conditions for 30 Years

Scipedia content — Tue, 22 Sep 2020 17:44:02 +0200

A model building made out of concrete block specimens whose surfaces were coated with various finishing materials was constructed for the outdoor exposure test. After 30 years of outdoor exposure, the deterioration of finishes and their carbonation and corrosion inhibition effects were investigated. As a result, the following conclusions were obtained: Though the deterioration levels differed depending on their types and thickness, all finishing materials showed some kind of deterioration after 30 years‘ long-term outdoor exposure. The progress of carbonation and corrosion are prevented when the surface is coated with finishing materials of sufficient thickness or waterproof effect. Regarding the relationship between corrosion depth and carbonation depth, corrosion is initiated after the carbonation front reaches the area. It usually takes a while to initiate corrosion in the carbonated area, not immediately after the carbonation reaction. When the concrete surface is properly coated with finishing material, corrosion may not be initiated in non-carbonated area in concrete where the pH level is not lowered.

Performance Based Specification of Wood – Project CLICKdesign

Scipedia content — Tue, 22 Sep 2020 17:43:54 +0200

This paper introduces the ForestValue research project CLICKdesign – delivering fingertip knowledge to enable service life performance specification of wood. The consortium is working on a primary innovation to move from the complex, fragmented and general to the easy-to-use, consolidated and specific by provision of a digital tool for specifiers. Other materials tackle this and provide designers and architects with software. The specification of performance of wood products is complex and fraught with inconsistency and requires use of multiple platforms for data, experience, standards and national recommendations. CLICKdesign will provide a tool that has within it the decades of research, the complexity of the standards specification systems and the variation of approach due to tradition, materials and culture across Europe and beyond. A simple tool for nonexpert public users will be available as well as a tool accessible to professional users that will be refined with industry to ensure relevancy and accelerate uptake and use.

Effect of the Type of Concrete with Mineral Additions on the Reinforcement Corrosion Induced by Chlorides - Analysis in the Same Mechanical Strength Class

Scipedia content — Tue, 22 Sep 2020 17:43:44 +0200

The environment in which the concrete structure is inserted has a great influence on its durability and its service life. Thus, the present work aims to study of the performance of 5 types of concretes of same compressive strength (35 MPa at the age of 28 days) and considers kinetic and thermodynamic aspects of the corrosion induced by chlorides. The 5 types of concretes studied were produced with the use of mineral additions in partial replacement on cement mass (10% of silica fume, 30% of fly ash and 20% of metakaolin), besides the control situation (without mineral addition). The water-to-cementitious materials ratio was different for the concretes ranging from 0.30 to 0.55. Specifically, for the concrete with fly ash, two water/binder ratios were studied (0.30 and 0.40) with the goal of verifying if there are or not significant differences on properties of corrosion with little change of water quantity in the mix. The chloride attack consisted by 308 days (44 weekly cycles) in immersion in aggressive solution rich in chlorides and subsequent drying in a laboratory environment. During this period, the corrosion potentials (Ecorr) and corrosion rate (icorr) from polarization resistance (Rp) of steel bars were monitored. As a general result, it was possible to compare the performance of concretes at the same class of compressive strength to denote which systems have the longest durability in view of attack by chloride. The results have shown that the concretes produced with mineral additions did not show steel bar corrosion, thus configuring major service life for them. Control concrete presented depassivation of reinforcing steel, Ecorr more electronegative and higher icorr over time.

Implementing a Framework for Qualitative Assessment of New Technical Solutions: A Case Study on CLT

Scipedia content — Tue, 22 Sep 2020 17:43:38 +0200

New technical solutions are introduced at a fast pace in the Swedish construction industry, mainly driven by issues concerning costs and productivity. These new technical solutions can comprise new materials, new goods, new designs but also new processes. The record of accomplishment when introducing new technical solutions in the industry is not unproblematic and serial failures of different new technical solution have occurred. In an earlier interview study exploring introduction of new technical solutions in the Swedish construction industry, a common lack of thorough methods for evaluation of new solutions was identified. To address this issue, a case study was performed, exploring a method of evaluation with respect to building physics while implementing a cross laminated timber frame in a multifamily building. The case study uses a framework of assessment with focus on building physics. This paper presents the findings from the case study focusing on how evaluation of a new technical solution with respect to building physics is performed, together with an evaluation of the method, using the experiences of the participants in the case study.

Assessment of Reasons behind and Level of Destruction of Aquatic Supports in a Hydraulic Ash Removal Bridge

Scipedia content — Tue, 22 Sep 2020 17:43:30 +0200

The presented article describes a case of damage to concrete in the aquatic supports of a hydraulic ash removal bridge in a power plant. Carrying out an assessment of the causes of concrete damage, as well as determining the possibility of the occurrence of corrosive phenomena within it, and thus, consequently, predicting the durability of the building structure and selecting, on its basis, a proper repair-renovation procedure, required a series of essential studies and analyses to be carried out. Therefore, in the analyzed case, a complex study was carried out on the structure as well as tests on samples of concrete cut out, in the form of core drillings, from the damaged structure (among others: macroscopic, microscopic SEM, XRD, DTA, chemical analyses). Based on these studies, the types of corrosion responsible for the analyzed damage were determined.

Possibilities of Reducing Energy Costs in the Life Cycle of Office Buildings

Scipedia content — Tue, 22 Sep 2020 17:43:23 +0200

Buildings absorb energy at every stage of the life cycle. The paper analyses the phases of the life cycle of an office building indicating the possibilities of reducing energy consumption. In particular, attention was paid to the most energy-intensive phase, that is the use phase. Both simple actions and more advanced solutions allowing to reduce the energy demand of a building during the use phase are characterized. For an exemplary office building, life cycle costs were calculated taking into account selected solutions improving energy efficiency.

A Probabilistic Model for the Evolution of Porous Structure Caused by Solid-Phase Precipitation/Dissolution within Building Materials

Scipedia content — Tue, 22 Sep 2020 17:43:16 +0200

Saline intrusion is a critical issue in building material because of the severe damages caused by the salt precipitation/dissolution process, especially for the porous material, which has good connectivity. When porous material is exposed to aggressive ambient, the pore structure, not only porosity but also pore size distribution, will be altered by salt precipitation/dissolution. As one of the most significant characteristics in the porous material, pore size distribution is always paid much attention in many literatures. However, a quantitative and practical determination method is still absent. This work aims to establish a probabilistic model to investigate the pore size distribution induced by solid-phase precipitation/dissolution. First, a lognormal distribution is proposed for the simulation of initial pore size distribution tested by the MIP method. Then we develop a probabilistic-based porous network to represent the evolution of microstructure due to precipitation/dissolution. To this end, two different transformation models are constructed to interpret the relation between initial pore radius and modified pore radius before and after precipitation/dissolution. With this probabilistic-based porous network, we could illustrate the precipitated profiles that evolve near the capillary interface during the salt precipitation/dissolution process for a given porosity and water saturation degree. Such a method could be used to interpret the mechanism of the local precipitation/dissolution process in pore scales, which cannot be implemented by experimental measurements.

Effect of Selected Moisture Reference Year on the Durability Assessment of Wall Assemblies under Future Climates

Scipedia content — Tue, 22 Sep 2020 17:43:06 +0200

Hygrothermal simulations are commonly used to evaluate the moisture damage risk of building envelopes over the long-term. For such assessment to be accurate, a proper selection of representative climate data is required. A common method is the selection of a moisture reference year from a set of available long-term climate data. For instance, the IRC-led research consortium MEWS (Moisture Management of Exterior Wall Systems) developped the Moisture Index (MI) approach, which consists of a wetting and a drying function. Therefore, the reference year selection would be based on the MI ranking. ASHRAE 160 is adopting a procedure named “the severity index” for the selection of moisture reference year. Combining climate loads and durability criteria, this method allows to select more “severe” weather years, thus providing a more representative ranking of the weather data. The objective of this paper is two-fold. First, to compare the selection of the moisture reference year based on two different approaches for both historical and future climate loads. Second, the effect of chosen representative years is evaluated and compared to long-term simulation periods (of 31-years) based on the durability of building assemblies. The methodology includes hygrothermal simulations of two different types of wall assemblies located in three different Canadian cities under a changing climate. In general, higher mold index values were obtained by the long-term simulation and MRYs using Isev. Comparing the results of different models under future climates, the three methods were in good agreement, except for a brick wall facing WDR in Ottawa and Vancouver. This might be due to the Isev correlations were developed based on a north-facing stucco wall. In addition, for a north-facing wall, an extremely low mold index was predicted for Vancouver, compared to WDR direction. Thus, considering a north-facing wall as a criterion for performance evaluation might misrepresent the reality in some locations. Hence, both WDR and North orientations should be considered. A further study will be carried out to investigate the performance evaluation of Isev method for different types of wall systems and orientations.

Modernization of Housing Estates Towards Sustainable Development: What do Housing Estate Managers Provide, What do the Users See?

Scipedia content — Tue, 22 Sep 2020 17:42:57 +0200

Modernizing multi-family residential estates in operation for about 40 years is a multifaceted and complex process. In Poland, these assets cannot be considered "degraded" yet, they are not an obvious object of deep retrofit actions. The literature on the subject and the author’s own research confirm that the management of Polish housing estates is carried out with the focus on current repairs and improving energy efficiency by insulating the buildings’ envelopes. Poland lacks long-term programs to implement retrofitting actions based on the analysis of both social and technical needs and aimed at improving the estate’s sustainability parameters. The author puts forward an original approach to the programming of sustainable housing stock retrofit based on the PEARS model (PeopleEnvironment-Actions-Resources-Sociology). The paper focuses on the social research part of the model and presents the case-based analysis – the results of the recurring survey conducted to provide input for sustainable planning of the estate improvements. The paper is a summary of over ten years of research and studies on practices of maintenance of infrastructure and buildings, changing user needs, and user opinions on the possible directions towards sustainable housing.

Analysis of Steel Bars in Corrosion Process after 70 Years of Natural Aging.

Scipedia content — Tue, 22 Sep 2020 17:42:50 +0200

Reinforced concrete structures are commonly used in civil engineering. However, the number of deteriorations in these structures is increasing, especially problems related to steel corrosion. Also, according studies, corrosion is responsible for about 3.5 % of annual GDP with recovery costs in world. Thus, this study analyzed the corrosion of steel bars at 70-year-old, which are in corrosion process by natural aging. Tests were performed to analyze the bars microstructure, using SEM and EDS, as well as analysis of the current mechanical characteristics, with tensile test. Through SEM, it was possible to measure the layer of the corrosion products formed at the samples edge, and to observe the fragility of this region, with the presence of several microcracks. EDS test contributed to verify the oxygen difference from the nucleus until to the specimen edge. It was possible to notice that in the edge, presence of oxygen is much greater. In the mechanical tests, by the tensile test, the samples do not reach the minimum elongation and the limit of resistance prescribed in the standard. Thus, it is believed after 70 years of natural aging, the samples are in advanced process of corrosion, with edges worn out, and no comply with the minimum mechanical requirements.

Experiences from Interior Super Insulation of a Brick Wall from the 1800s

Scipedia content — Tue, 22 Sep 2020 17:42:43 +0200

Many brick buildings in Sweden today face a large need for renovation measures to prolong their service life and make other uses possible. Conventional thermal insulation materials, such as fibre glass and EPS, demand a thick layer of insulation to reach the energy targets. Super insulation materials, such as vacuum insulation panels (VIP) and aerogel blankets (AB), are thermal insulation components with a 3-10 times higher thermal resistance than conventional insulation materials. In this study, the effect of interior insulation using super insulation materials is investigated, using experiences from a case study in a brick wall from the 1800s. Earlier research has shown that interior insulation decreases the drying-out capacity of an exterior wall and increases the risk for freeze-thaw damages in brick walls. The case study building is an industrial building from 1896 with 470 mm homogeneous brick masonry walls insulated with both aerogel insulation and with vacuum insulation panels. Six heat flux sensors were installed in the wall and used to evaluate the thermal resistance of the wall with and without insulation. The initial measurements showed that the rate of water flow in the bricks is approximately three times higher than that in modern bricks. The average calculated U-value was reduced by 70% for the AB and 81% for the VIP layers, while measurements at the three occasions gave a reduction of 72-83% for the AB and 72-84% for the VIP layers, i.e. in the same order of magnitude.

Various Factors of Water Entry and Penetration Through Water Proofing Layer in Wooden Wall Assembly

Scipedia content — Tue, 22 Sep 2020 17:42:35 +0200

Rainwater entry and penetration through a waterproofing layer, such as external finishing and sheathing membrane, should be avoided to prevent moisture damage to a wooden wall assembly. However, housing warranty insurance organizations in Japan have reported that deterioration in some wall assemblies was caused by rain penetration, and severely damaged walls were detected in airtight and insulated building envelopes. This paper presents various factors of water entry and penetration of the waterproofing layers in wooden wall assemblies in terms of practical situations, as a part of a research project to reveal the risk of water and moisture accumulation in collaboration with government and industries in Japan. Several experimental works using mock-up specimens replicating a part of the wall assembly were carried out. As for external finishing, the water intrusion was observed not only at the joints but also at the bottom of vented cavities. Although these minor defects must be prevented by proper design and site work, it is difficult to avoid them completely through the construction process and period of use. Indeed, the extent of water entry was affected by various factors such as wall configuration, exposure conditions and so on. Experimental results suggested that various factors, including detail of interface and quality of materials, should be considered to assess service life prediction by hygrothermal analysis.

Biodegradable Polymers on Cementitious Materials

Scipedia content — Tue, 22 Sep 2020 17:42:28 +0200

Nowadays the sustainability and safety requirements of structures inspire the study of new self-healing materials and preventive repair methods on cementitious elements. To achieve this undertaking, this research replaces widely employed synthetic polymers by biodegradable ones as consolidants and water-repellents, and assesses the protection and consolidation effect of biopolymers (obtained by using waste biomass of mixed microbial cultures from polyhydroxyalkanoates production processes) as eco-friendly healing agents by analysing the water absorption of two kind of materials. The first group of samples are cement mortar specimens whose external surface has been treated with biopolymer products and subsequently evaluated by water drop absorption test. The second group of samples are cement mortar specimens formulated with biopolymer products included in its mixing water and later the waterproofing efficiency is analysed by capillary water absorption tests. The water absorption behaviour of both kind of samples shows a potential improvement of cementitious elements durability, since water absorption results have decreased for treated samples in comparison with untreated ones.

Two-Part Bio-Based Self-Healing Repair Agent for Cement-Based Mortar

Scipedia content — Tue, 22 Sep 2020 17:42:21 +0200

Factors affecting durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks are one of the main reasons for a decrease in service life in concrete structures. Therefore, it is crucial to detect and recover microcracks, then to repair them as they were developed to wider cracks. Recent research in the field of concrete materials suggested that it might be possible to develop a smart cement-based material that is capable of remediate cracks by triggering biogenic calcium carbonate (CaCO3) precipitaton. This paper summarizes a study undertaken to investigate the self-healing efficiency of Sporosarcina pasteurii (S. pasteurii) cells immobilized on both diatomaceous earth and pumice, to remediate flexural cracks on mortar in early ages (28 days after mixing). To obtain a two-phase bio additive, half of the minerals were saturated with a nutrient medium consisting of urea, corn-steep liqueur(CSL) and calcium acetate and the cells with immobilized to the other half without nutrients. Screening of the healing process was done with ultrasonic pulse velocity (UPV) testing and stereomicroscopy. With this approach, the cracks on mortar surface were sealed and the water absorption capacity of the so-called self-healed mortar decreased compared to its counterpart cracked mortar samples.

Large Scale Laboratory and Field Tests of Aerogel Renders

Scipedia content — Tue, 22 Sep 2020 17:42:13 +0200

Within the framework of the European project Wall-ACE a large-scale laboratory test (EOTA-Wall Test) was performed. Additional a test field in Switzerland was equipped with six different aerogel renders by the project partner AGITEC. Laboratory walls and test field were equipped with sensors to monitor in real-time climate, heat flux, temperature, relative humidity, and at the laboratory tests additional material moisture. The data allow calculating U-values and material parameters as well as drying behaviour of render and substrate. During and after the artificial weathering in laboratory the renders were subjected to visual inspection and mechanical adhesion tests. The performance of the aerogel renders will be assessed and compared with results on conventional insulation renders.

Deterioration Prediction Model of Multi-Layer Coating Material and its Reference Service Life Evaluation in Terms of Carbonation Control Effect

Scipedia content — Tue, 22 Sep 2020 17:42:06 +0200

In this paper, authors propose a method to predict deterioration of exterior finishes using Markov Chain Model based on field survey results on cracks of exterior finishes of existing RC buildings. There existed correlation between degradation of finishing and carbonation progress. Authors propose the service life prediction approach to focus on the carbonation suppression effect into the concrete considering progress of exterior finish deterioration.

Compressive Strength Improvement and Water Permeability of Self-Healing Concrete Using Bacillus Subtilis Natto

Scipedia content — Tue, 22 Sep 2020 17:41:57 +0200

In recent years, many projects have been carried out to enhance the durability of concrete structure from the influence of cracks. Generally, managing cracks should be a rather preventative method for sustainable development. Based on that, Bacillus subtilis natto - a local bacterium in Japan was found to have the ability to form CaCO3, which can be used as healing materials for cracks in the concrete structure. The bacterial biomineralization immobilized in lightweight aggregate was studied to improve the compressive strength by healing the cracks and densifying the structure. Moreover, as an essential parameter for durability enhancement, the water permeability of self-healing concrete through a water-flow system was carried out. Experimental results on the behavior of the materials indicate that Bacillus subtilis natto could lead the compressive strength to 40 % higher than the controls. Promising result in preventing the water through the cracks confirmed the self-healing effect with more potential in larger-scale.

Drying Potential of Wood Frame Walls Subjected to Accidental Water Infiltration

Scipedia content — Tue, 22 Sep 2020 17:41:47 +0200

Wood frame construction is the most widespread building method. In Belgium the number of wood frame buildings has grown in the last years: in 2018 over 10% of all new built dwellings were wood frame buildings. This increase can be partly attributed to the growing attention for energy performant buildings with a low environmental impact. In contrary to masonry construction, wood frame is more vulnerable to moisture problems, mould growth and wood rot. An important risk is water infiltration through imperfections in the building envelope as a result of driving rain. Therefore it is important for the design to be resilient and allow drying without consequential damage. To analyze the drying potential, an experimental set-up with 8 wood frame compartments was built. The compartments differ in the type of insulation material (mineral wool or cellulose) and the type of vapour retarder (OSB or smart vapour retarder) that were used. In this way 4 types of compartments were obtained, each having a different combination of insulation and vapour retarder. Of each combination there are 2 identical compartments. This allows to insert water in one of both, to mimic rain water infiltration from the outside into the compartment. Temperature, relative humidity and moisture content were measured on different locations in the construction (in total 92 sensors). In this way, the hygrothermal performance of the compartments with and without water infiltration can be analyzed, as well as the drying rate.

Evaluation of Socio-economic Impacts of Incidents on the Railway Infrastructure

Scipedia content — Tue, 22 Sep 2020 17:41:39 +0200

Evaluation of the economic efficiency of investment projects in transport infrastructure in the Czech Republic is methodically based on the Departmental Methodology of the Ministry of Transport. Economic cash flows, generated in accordance with the CBA principles, are modelled within this methodology on the basis of the evaluation of socio-economic impact of individual projects. In the case of the railway infrastructure constructions, the socio-economic impacts used by the methodology do not include benefits associated with increasing safety and reliability of the railway infrastructure network due to new security systems implementation. Determination of socio-economic impacts associated with specific types of incidents on the railway which are caused by insufficient railway infrastructure security and which could be eliminated by the implementation of the higher-level signaling equipment forms the subject of the research. The research is based on the analysis of a database of incidents occurring on the railway in the Czech Republic in the 2009 – 2018 period, which describes the basic impacts associated with a particular incident. Statistical data on the railway infrastructure is also used to determine the impact of incidents in addition to the database. The key outcomes of the research are the determination of methodological steps for the evaluation of the impacts of incidents on the railway and a case study for their verification. Future research will focus on making evaluation of the abovementioned benefits more detailed. Research outcomes will improve decision-making process on selection and financing of the projects related to railway infrastructure safety for their future implementation.

Assessing Water Resistance and Surface Properties of ETICS

Scipedia content — Tue, 22 Sep 2020 17:41:31 +0200

External Thermal Insulation Composite Systems (ETICS) contribute significantly to building energy efficiency by increasing thermal insulation, correcting thermal bridges and reducing interior water condensation. Additionally, these solutions protect the structure and thus enhance the durability of the building. The use of ETICS remarkably increased in the last three decades also due to the introduction of new international and national regulations on building energy efficiency (e.g. EU Directive on the Energy Performance of Buildings). ETICS are constantly exposed to weathering (e.g. wind, rain, sun light) and anthropic factors (e.g. graffiti, environmental pollutants), which can lead to cracks, biocolonization and stains and thus affect ETICS durability. However, international technical documents on the evaluation of the effectiveness and durability of ETICS do not consider the possible synergies between these factors, which can trigger and speed up multiple biological, mechanical and chemical degradation processes. With the aim of filling this gap, this paper focused on the water resistance and surface properties of several ETICS surface coatings, verifying possible connections between these factors. The moisture transport properties (capillary water absorption, water vapour permeability, and drying kinetics) and surface properties (colour, brightness and roughness) of some commercially available ETICS were tested. This study is part of a wider research project (WGB_Shield: resistance for water, graffiti and biocolonization of external thermal insulation systems) that aims at the development of ETICS with improved durability in urban environment.

Durability Assessment of GFRP Rebars Exposed to High pH-Seawater

Scipedia content — Tue, 22 Sep 2020 17:41:22 +0200

There is a continued process to implement innovative materials to enhance the sustainability and durability of the built infrastructure. Technologies developed over the last two decades have facilitated the use of glass fiber reinforced polymer (GFRP) composites as internal reinforcement bars (rebars) for concrete structures, which have proven to be an alternative to traditional steel reinforcement due to significant advantages, such as magnetic transparency and, most importantly, corrosion resistance, equating to durability and structural life extension. This study evaluates the durability of three different available and most commonly used GFRP rebar types, based on exposure to aggressive environments, such as those experienced in coastal areas. For that, the specimens were expose to high pH seawater solution (that simulates the alkalinity of the concrete exposed to seawater), at 60 ºC for different periods of time: 45, 90, and 180 days. The durability of these GFRP rebars was assessed by testing four different physio-mechanical properties, including: tensile strength, elastic modulus, and transverse and horizontal shear strength. Preliminary results show that the resilience of the GFRP rebars after being exposed to high pH seawater at high temperature, varies considerably among the three different types. The tensile strength was the most affected physio-mechanical property.

Client’s Expectations vs Contractor’s Pricing. Fair Prices or Bid Rigging

Scipedia content — Tue, 22 Sep 2020 17:41:14 +0200

The road construction sector is a specific part of the construction industry. It happens very rarely that a section of a road is financed also by a private entity. The other factor distinguishing it – is a significant value of road construction contracts. The Client’s estimates of the value of the prospective contracts have to be based on the market prices in case of public procurement. However, this market is dominated by public orders. There is no comparison to the value of works ordered on the private part of the construction market, which is found more efficient by economists. Widely applied the “design and build” type of orders make the comparisons of the unit prices more difficult. The huge differences between the Client’s estimates and the winning prices in the road construction public tender procedures are the bases of speculations about the fairness of the procedures. These differences can have a varied origin. There are several reasons for them e.g. varied contractor’s risk, the size of the structure, type of order, the dynamics of the road construction market. Nevertheless, fraudulent practices can make the winning price much higher than the Client’s estimate. The article is an attempt to finding the limit i.e. what part of these differences can be explained by fair, market reasons. If the found limit is exceeded, it should make the Client carefully consider the offers placed. The analysis is based on collected data concerning almost 400 tender procedures for the sections of roads in Poland in 2014-2017.

Freeze-Thaw Deicing salt Attack on Concrete: Towards Engineering Modelling

Scipedia content — Tue, 22 Sep 2020 17:41:06 +0200

In order to reduce carbon dioxide emissions, the construction sector is increasingly using clinker-reduced concretes. Concrete with high amounts of ground granulated blast furnace slag (GGBFS) show increased durability performance in certain environmental conditions compared to concrete with Ordinary Portland cement (OPC). However, in laboratory studies, concrete with GGBFS show an increased initial scaling rate in comparison with OPC concrete. Changing weather conditions and high relative humidities > 70 % in field lead to less carbonation and thus, to a better freeze-thaw deicing salt resistance (FTDSR). Therefore, the current lab performance test penalizes GGBFS concrete. This contribution studied the impact of carbonation and intermittent dry periods on FTDSR of GGBFS concrete compared to that of OPC concrete. It could be shown that for concrete with OPC, intermittent dry periods lead to an accumulation of salt in the near surface, which causes a reduction of the scaling. GGBFS concrete, on the other hand, shows an opposite behavior: carbonation causes an increase in scaling after the dry period. GGBFS concrete samples with CO2-free pre-storage show the lowest scaling of all samples investigated. A better simulation of the behavior of GGBFS concrete could lead to economical as well as optimized solutions for the local environment conditions and enable the large-scale use of more environmentally-friendly concretes. Therefore, by taking the effect of carbonation and intermittent dry periods into account in a simple engineering model, the prediction of concrete scaling under consideration of real climatic conditions is possible in an eco-efficient manner.

Durability Studies of Self-Compacting Concrete containing Electric ArcFurnace Slag Aggregate

Scipedia content — Tue, 22 Sep 2020 17:40:57 +0200

The structure of self-compacting concretes containing electric arc-furnace slag, their mechanical behavior, and their durability are all studied in an extensive experimental campaign, to evaluate the suitability of three concrete mixes for use in real construction works. Specimens manufactured with self-compacting electric arc-furnace slag concrete are subjected to wetting-drying and freezing-thawing test procedures, for their study in aggressive environments, especially marine environments. In general, all the test results were quite encouraging. It was once again demonstrated that the use of electric arc-furnace slag in concrete represents an opportunity to reduce both the volume of siderurgical waste generated in our society, and the consumption of fresh raw materials.

OSB and Marine Plywood: Performance Comparison for use with Light Steel Frame Walls in Brazil

Scipedia content — Tue, 22 Sep 2020 17:40:48 +0200

The use of light steel frame and wood frame in Brazil is still recent, hence there is little information about the durability of these technologies applied in Brazilian climate conditions. The wood-based boards are used as a part of the light steel or wood frame walls and are designed to contribute to the wall structural behavior (horizontal reinforcement and resistance to suspended loads). Once the information if such boards meet the DL (design life) set in the Brazilian code of residential building performance is still unknown, this paper analyses the technical characteristics of two woodbased boards - OSB and marine plywood - aiming to gather more information concerning durability under liquid water action. Thus, tests were carried out on samples of these two boards to evaluate their behavior against liquid water and after accelerated ageing test. In all cases, OSB showed to be more sensitive to early degradation than plywood.

Uncertainty and Sensitivity Analyses for Evaluating the Building Element‘s Replacement in Building LCA

Scipedia content — Tue, 22 Sep 2020 17:40:38 +0200

This paper presents a systematic way to consider the uncertainties of the building elements‘service lives within a stochastic framework, by defining the corresponding probability density functions, based on a service life database. This methodology is appropriate for screening and detailed building LCA, since the service life database offers the possibility to define the probability density functions of the service lives, in different level of details

Composite Façade Elements with Self-Cleaning Surface made of UltraHigh-Performance Concrete (UHPC)

Scipedia content — Tue, 22 Sep 2020 17:40:29 +0200

In the framework of the European project H-House various concrete façade elements were developed with the aim to ensure a long service life by combining a very durable material with selfcleaning properties. The façade elements presented are made of a shell of UHPC filled with blocks of aerated autoclaved concrete as insulating material. Self-cleaning properties were realized amongst others by imprinting a microstructure into the surface during casting. The paper focuses on selected technological aspects of the manufacturing process of prototypes which had to be performed in two concreting sections. Furthermore the challenges faced when upscaling the self-cleaning properties are addressed and the strategy to assess the self-cleaning properties by measuring the contact and the rolloff angel is presented. The results show that a successfull upscalaing process requires detailed planning and that the best results can often be achieved with a moderate work effort or material use.

Macrocell Processes in Reinforced Concrete Structures

Scipedia content — Tue, 22 Sep 2020 17:40:17 +0200

Corrosion of steel embedded in reinforced concrete is the phenomena that most affects the durability of this type of structures. The control and analysis of the rebars can help detect this problem beforehand, contributing to prevent costly repairs made when the damage is quite advanced. Currently, there are several techniques for measuring the corrosion rate of steel, but they have the disadvantage of being slow or requiring specialized tools. In addition, these techniques need direct connection to the rebars, so removing the concrete cover layer is necessary. This destructive technique is sometimes impossible to do because there are analysis zones which are inaccessible due to they are buried or submerged. Recently, using sensors embedded previously casting and external electrical connections let analyse the corrosion without using invasive techniques. This study presents the complementary technique of analysing macrocell currents in order to know the origin and direction of current in reinforcements. This technique requires less time and non-advanced material, only an ammeter and electrical connection to the rebars, executed before casting. In addition, this parameter provides information about the real corrosion of the different parts of the structure. In this study it is performed the laboratory analysis of this technique by the use of specimens containing one anode and one cathode inside them creating a macrocell. The influence of different environments on macrocell current intensities shall be studied and compared with other studied parameters as corrosion density.

Evaluation of Pore Structure of Hardened Cement Paste Immersed in Sodium Sulfate Solution

Scipedia content — Tue, 22 Sep 2020 17:34:56 +0200

The purpose of the present study is to evaluate pore structure of hardened cement paste immersed in sodium sulfate solutions and to experimentally examine the relation between the change of pore structure and hydration products. Cement paste specimens were immersed in sodium sulfate solutions and ion-exchanged water for two weeks. Since oxygen gas can pass through the pores having micro scale, it is possible to evaluate the effect of the pore structure on the oxygen transport in cement pastes. Thus, the oxygen diffusion coefficient (DO2) of the specimens after immersion were measured, and the pore volume and the pore size distribution were also measured. In addition, the phase compositions of the specimens were acquired. As a result, DO2 of the specimens immersed in the sodium sulfate solutions decreased as compared to the specimens immersed in the ion-exchanged water. The tortuosity of the specimens immersed in the sodium sulfate solutions increased due to decreasing of the pore volume having a diameter larger than 20 nm. There was a correlation between the volume of ettringite and the pore volume having a diameter larger than 20 nm. According to the above results, it was considered that the decreasing of DO2 in the case of sulfate immersion can occur as a result of the complication of the pore structure owing to filling of the pores by ettringite

Development of an Apparatus for Measuring the Load Acting on Joint Sealant when Movement Occurs

Scipedia content — Tue, 22 Sep 2020 17:34:49 +0200

The sealant that fills the joints of an exterior walls of building is subjected to weather loads, such as sunlight, ambient temperature, and rain, as well as a movement of the joints. As a result, the sealant gradually deteriorates under the combined deterioration factors of weathering and movement. Meanwhile, the results of a 15-year outdoor dynamic exposure test conducted in Japan using the methodology of ISO 11617 showed that the progress of damage varies greatly depending on the type of sealant and the stress relaxation rate. However, the mechanism of damage progression is unclear. In the present study, we focused on the load when the sealant moves and developed a load-measuring apparatus as the first step in clarifying the relationship between the progress of damage and the load. The load was measured at −20, 23, and 40 °C for test specimens with different stress relaxation rates, and it was confirmed that the developed load-measuring apparatus was able to measure the load correctly. Furthermore, it was shown that it is difficult for the stress of the sealant with a high stress relaxation rate to relax over time at low temperature but easy at high temperature, and the load increases when switching from the compressed state to the extended state.

Durability of FRP Immersed in Water. Changes in Mechanical Properties

Scipedia content — Tue, 22 Sep 2020 17:34:42 +0200

Fibre Reinforced Polymers (FRP) have been widely used to strengthened construction structural elements in the last years because of their mechanical pros. However, the durability of these materials is always controversial. In particular, the effect of long-term contact with water on the mechanical properties of FRPs is studied in this research throughout the implementation of accelerated degradation tests. Samples of Carbon FRP and Glass FRP were immersed into supply water, water with salts and surfactants and highly chlorinated water. In all cases, electrical current passing through the samples was also imposed. Tensile tests on pristine and degraded samples were carried out to determine the influence of these aggressive environments on the tensile strength and the Young‘s modulus of the specimens. Finally, superficial (ATR) FT-IR analyses were conducted to assess possible chemical changes in the samples surfaces. Results indicated that the chemical composition of used resins was not modified due to the water exposure. No hydrolysis process took place during testing time on the surface. However, mechanical properties were reduced, especially when samples were exposed to plain supply water, which may be related to the physical degradation caused by moisture intake by diffusion.

Risk-Based Approach for Improving Concrete Bridges‘ Inspection Planning

Scipedia content — Tue, 22 Sep 2020 17:34:35 +0200

Visual inspection forms the basis of the inspection planning process for concrete bridges. The authority responsible for bridge inspection maintains a database to record past inspection results, in order to plan future inspections. It is a challenge to recognize and classify bridges that it is essential to inspect based on inherent requirements. This is further exacerbated by the limited budget available. This manuscript describes a methodology for classifying bridges based on risk of potential failure and distributing the annual inspection budget for carrying out inspections on bridges accordingly. The absence of such a methodology allocation of resources for bridge inspection without real need. For example, on some occasions it is not necessary to inspect certain bridges on a time basis. Hence, this study focuses on developing an inspection-planning approach based on the actual and predicted condition (i.e. based on the database of past inspection data). It enables the bridges to be classified into different categories, based on the risk of potential failures. This enables the effective distribution of annual budgets among the bridges, avoiding unnecessary inspection that incurs pointless inspection costs.

Earth Construction Durability: In-Service Deterioration of Compressed and Stabilized Earth Block (CSEB) Housing in Algeria

Scipedia content — Tue, 22 Sep 2020 17:34:27 +0200

The present work deals with a unique in-service valuation of CSEB structures in Algeria. The inspection tries to bring out the impact of long time exposure under different and opposite climate and micro-seismic contexts. The diagnosis methodology is inspired by the approach largely adopted for the rehabilitation of traditional architecture. It involves the compilation of the previous survey reports, visual inspection of the structures, in-situ and laboratory tests to assess the residual CSEB mechanical properties. The CSEB constructions are located in the coastal north and the desertical south part of Algeria and were exposed respectively to a long-term Mediterranean and Saharian climate. The results of the investigation show that the CSEB in the construction located in the northern region is increasingly altered by the humidity. As the relative humidity rises, the fouling layers grow over some level. The surface pitting which is the consequence of long exposure to the wetting/drying cycles is also observed. The outer surfaces of the walls were honeycombed which reduce drastically the block resistance against the abrasion test. In some cases, differential erosion appears in the front of the walls, which indicates that the alteration does not proceed at the same rate from one area of the block to the other. However, owing to highly cementitious mortar used to join the earth blocks, the edges and corners remain unchipped. In the southern region where the arid climate dominating, the degradation of the CSEB is less prone to water attack but roughly exposed to the effect of the winddust frequent in this region and to the unawareness of the population. The paper presents also some recommendations to improve the earth construction durability with CSEB technique.

A New Alkali-Silica Reaction (ASR) Mitigation Technology - Part I: Comparing with Li, Ca, Al Salts, and Densified Silica Fume

Scipedia content — Tue, 22 Sep 2020 17:34:20 +0200

Alkali-silica reaction (ASR) is a major concrete durability problem. The occurrence of ASR results in significant maintenance and reconstruction costs to concrete infrastructures all over the world. Ever since Stanton (1940) discovered the expansive characteristics of ASR in 1940, there has been much speculation as to the cause and actual mechanism of expansion. Current market solutions are not always sustainable, such as hauling non-reactive aggregates or fly ash from long distance; or use of Li-based chemical admixture that is facing challenge of raw material‘s availability. The current article will present a patent pending technology which provides a commercial solution for mitigating the ASR. The ASR mitigating effect of this technology is compared with lithium, calcium, and aluminum salts, and densified silica fume.

Thermodynamic Processes in Nanostructured Thermocoatings

Scipedia content — Tue, 22 Sep 2020 17:34:12 +0200

In the 21st century, global climate change and the high level of fossil energy consumption have introduced changes affecting all sectors of the economy, including the building industry. This process has prompted EU members to create strict regulations in building energetics. It has become a serious task for architects to find more effective ways for thermal insulation. One of these options is the application of nanostructured materials. Among them nano-ceramic thermocoatings open a wide range of research fields, because complete agreement had not been already found about their insulating effect. In order to explore and describe the thermodynamic process inside nano-ceramic thermocoatings 6 series of heat transfer resistance experiments were performed in 2014-2018. Several building structure configurations with 12 different orders of layers were tested with a standard heat flow meter. On basis of these results it could be concluded that in case of nano-structured thermocoatings convective heat transfer coefficient might be taken account in different way than in case of traditional macro-structured thermal insulation materials. Based on research results, the limits of its applicability can also be concluded. It has also been found that the insulating effect of nanostructured thermocoatings depends on the material characteristics of the insulated surface.

Probabilistic Approach to the Service Life Prediction of Timber Claddings

Scipedia content — Tue, 22 Sep 2020 17:33:25 +0200

The service life of buildings and components is extremely difficult to model and predict, mainly due to the uncertainty and variability associated with the degradation phenomena. These uncertainties are usually related with the intrinsic randomness of natural phenomena, such as the environmental degradation agents. In order to deal with these uncertainties, in this study, a stochastic approach is used, to model the service life of timber claddings. For this purpose, a logistic regression analysis is used to evaluate the probability of timber claddings to reach the end of their service life over time. Moreover, the impact of the environmental exposure conditions (e.g. facades orientation, distance from the ocean, exposure to damp and exposure to wind/rain action), which influence the degradation and service life of timber claddings, is also evaluated. The proposed models are applied to 150 timber claddings, located in Valdivia (South Chile), which have been analysed during an extensive fieldwork survey. The results obtained in this study aid the definition of maintenance plans, in a technically informed manner, in order to promote the conservation of these claddings, which are an important symbol of the local identity of this region, depicting a complexity of cultural values, inherited by Spanish and German colonisations.

Maintenance-Oriented Design in Architecture. A Decision Support System for the Evaluation of Maintenance Scenarios Through Bayesian Networks Use. A Case Study: the Headquarters of ING Groupe in Amsterdam

Scipedia content — Mon, 21 Sep 2020 13:24:50 +0200

This study was developed at the Department of Architecture of Pescara and Department of Energy, Systems, Territory and Construction Engineering of the University of Pisa as part of an experimental thesis that led to the implementation of a Decision Support System. The objective of the work was to implement a tool capable of evaluating - in relation to the choices concerning the morphology of the building, the construction technologies, the materials and the design of the architectural elements - the levels of maintenance quality implemented in the various phases of the project, from the first phases, in which few relevant decisions are made, to the executive phase characterized by a multiplicity of choices. The aim was to construct a tool in which the reliability of the evaluations was related to the quantity and quality of the data that feeds the decision-making process, but which is also able to evaluate preliminary decisions based on the elements of choice that characterize the first phases of the project. The conceptual model has been defined through the construction and implementation of a Bayesian Network or a graphical system of probabilistic inference able to represent the set of stochastic variables and their conditional dependencies through the use of a direct acyclic graph. Through the interrogation of the network it is therefore possible to evaluate through the expression of a synthetic index, a real overall rating of the different aspects that contribute to define the maintenance quality. The use of Bayesian Networks, in the light of the analyses carried out on an experimental basis - exemplified here on the case study of ING Groupe headquarters - for the ability to control a multitude of factors linked to the durability of materials, the morphology of systems and ease of intervention, seems capable of generating useful, effective and expandable tools to support the design decision-making process.

Smalti Murano Glass Tessella’s Applied Outdoor in the Trencadís Catalan Modernism Mosaic: Recognition of Preliminary Alteration Patterns

Scipedia content — Mon, 21 Sep 2020 13:24:37 +0200

This contribution presents previous results of a study carried out with the aim of achieving better results in the restoration processes by replacing the tiles of an exterior mosaic tiling of the Trencadís type of Catalan Modernism. In this case the trencadís tiles come from the cutting of pieces, called piastras, of opaque and mass-colored glass called Smalti Murano glass. These companies have extensive color catalogs that, although not exactly the same as they were a century ago, are close enough for these replacement tasks. Each color corresponds, however, to a different composition of glass and a slightly different manufacturing process. These differences favor that the differences of color always go accompanied also of differences of superficial aspect. However, not all color references currently available have the same surface quality since this product, during its manufacture, acquires primary defects typical of artisanal processes. So far the predominant criteria for the selection of the new references of piastras that must replace the product damaged by the extensive exposure to the weather as a coating are based primarily on color. However, durability requirements must also be part of the selection criteria for substitution references. The primary defects that a product already presents in its superficial quality are often indicators of either a more irregular quality or of circumstances that favor the early appearance of secondary defects throughout its useful life. The main objective of this study is to ensure, in restoration work by substitution, the selection of the best piastras from the point of view of surface quality, to apply on site the most similar tiles of tone and with greater durability. This study is part of a collaboration between the study group LiTA (Laboratori d‘Innovació i Tecnologia de l‘Arquitectura) (UPC) and a private non-profit organization.

Post Peak Behavior of Carbonated Concrete Structure - A Case Study of the Former Shime Mining Office Vertical Derrick in Japan

Scipedia content — Mon, 21 Sep 2020 13:24:29 +0200

This paper is a report on the investigation results of the Former Shime Mining Office Vertical Derrick, which was built in 1943 and was 75 years old at the time of the investigation. The building suffered from serious deterioration including rebar corrosion, which led to large area of concrete spalling. In this report, aggregation data of concrete spalling has been presented along with the investigation results of cover thickness. According to the investigation results, concrete spalling occurred in places where cover thickness was less than 25 mm. And According to the aggregation data, concrete spalling flakes increased by approximately 200 pieces per year, with the average size of 10 cm in diameter. Also, a possible relation between concrete spalling and rainfall was observed during the investigation. Equations using the proportion of wet area affected by rainfall to estimate the area of spalling are proposed, although the value of empirical coefficientαneeds further discussion, including collecting data from other buildings where spalling occurs.

Determination of the Deterioration Characteristics of Facade Materials: A Case Study

Scipedia content — Mon, 21 Sep 2020 13:24:23 +0200

Deterioration of the facade materials of a building and its importance are topics that are not getting the attention that they deserve and need. If a material can’t meet its accepted performance criterion during its service life then deterioration may occur on the surface, inside, under or at the structure of the material. Environmental, construction related, and human related agents collaborate with the mechanisms and make an effect which concerns the durability. Therefore, detecting the deteriorations of the materials play an important role for the maintenance planning. This study aims to detect the agents, mechanisms and effects of the deteriorations of a case building. A systematic approach was developed by making literature review. Hostile environmental analysis and building facade inspection have been made by the visual observations on a specific day. Deteriorations occurred at granite, wood composite, aluminum, glass and ceramic materials have been discussed.

Case Study of Pathological Manifestations of Neoprene Support Devices in Infrastructure

Scipedia content — Mon, 21 Sep 2020 13:24:16 +0200

The so-called works of special arts, are constructions of high complexities that allow the advancement of widening gaps and overcoming obstacles previously unthinkable. With the increase in magnitude of these structures, in addition to greater investments, the maintenance of these structures becomes an increasingly important factor for engineering. Among the elements of bridge structures, the support devices are components with important structural functions, being essential for their proper functioning and especially the durability of the entire structure. This paper aims to evaluate the pathological manifestations in support devices so, according to inspections performed and the diagnosis of causes, define their best practices and treatments for the maintenance and mitigation of the pathologies found. In the practical study the following steps were performed: survey and selection of the structures currently under maintenance of MetrôRio; selection of criteria for the evaluation of pathologies; carrying out inspections; comparative analysis between the viaducts to determine the priority order for negotiations; and definition of conduct. The results obtained were the result of evaluation of the field analysis, diagnosis and comparison with tests performed in support devices. Having as input the tests in the support devices, the best treatments and suggestions to avoid new pathologies were proposed.

Deformation Velocity Survey in Mortar and Cement Paste Specimens Subjected to External Aggressive Attacks

Scipedia content — Mon, 21 Sep 2020 13:24:10 +0200

The durability of concrete depends not only on the composition of the material and its resulting porosity, but also on the environmental conditions. Contact between concrete or cement mortars with water and soils containing sulphates, of a natural, biological origin or deriving from pollution, can activate chemical reactions in the cement paste inducing an expansion and degradation of the concrete. To evaluate the behaviour of the cementitious material subjected to various external aggressive attacks, prismatic samples of cement paste and mortar samples produced with the same binder (Portland cement) were immersed in demineralised water and in various solutions containing 5% and 10% sodium sulphates. Their expansion was monitored over time by a direct length measurement. This paper shows the results achieved in a rather long laboratory investigation and a first hypothesis has been formulated on the possible expansion rate in the first 56 test days and in the following 850 days.

Innovative Approaches to Increase Service Life of Poplar Lightweight Hardwood Construction Products

Scipedia content — Mon, 21 Sep 2020 13:24:03 +0200

During the second half of last century the forestry-wood chain has evolved and today ecosystem services in a sustainability framework are important. Forests are intended to provide services for the bio-economy, human health, biodiversity and climate control. An increased need for more renewable resources both for material and energy use has initiated extra interest for the potential to produce more lignocellulosic biomass, in short to increase wood production. One option is to provide in complementary production in planted forests. Both forestry and agriculture can take part in this. The cultivation of poplar hybrids in the temperate regions is a key option for the current and future bioeconomy. These fast-growing trees are producing lightweight hardwood with a low natural durability, but with an important potential as construction material especially as engineered wood products. All wood protection methods are of interest to be evaluated for this wood resource, making it suitable even for high quality applications. Poplar, for many reasons, has been nominated as hardwood with the best potential to perform similarly as softwoods for applications in wood construction. Benchmarking with wood species like spruce is relevant for several engineered wood products like plywood, LVL and even CLT. Wood treatments to increase durability have evolved from traditional wood preservation towards modification techniques such as thermally modified timber. Innovative poplar based products have been assessed on their performance and are designed to fit for purpose in relation to a specific combination of use class and service life. Introducing innovative poplar based construction product for green building requires adequate testing tools. Performance based assessment should allow to integrate different protective measures. Related to moisture dynamics and the linked fungal decay risk, opportunities to extend service life are manifold. Treatment can be differentiated e.g. for cladding (building envelope) and loadbearing construction components. Simple or sophisticated modification processes can alter the equilibrium moisture content. The use of wood based panels and new engineered wood products allow for better moisture control impacting fungal decay risk, but also alter the probability of insect damage. This paper intends to present several innovative poplar based construction products and show some cases of benchmarking in relation to an integrated service life approach.

Effect of Mortar Age on the Textile-to-Mortar Bond Behavior

Scipedia content — Mon, 21 Sep 2020 13:23:56 +0200

Textile-reinforced mortar (TRM) composites have received extensive attention as a sustainable solution for seismic strengthening of masonry and historical structures. This new system is composed of textile fibers embedded in an inorganic matrix and is applied on the masonry and the concrete substrate surface as an externally bonded reinforcement (EBR) system. The bond at the textile-to-mortar interfaces is the main stress-transfer mechanism and, therefore, should be thoroughly investigated. Furthermore, the effectiveness of TRMs in improving the seismic performance of existing structures is highly dependent on the durability of its components, materials, textile-to-mortar bond, and their long-term behavior. Due to the novelty of these materials in application to masonry structures, several aspects related to the durability and long-term performance of them are still not clear. To that end, a new study has been launched that looks at the time effect on the mechanical properties and bond behavior between fiber and mortar. For this purpose, two different hydraulic lime-based mortars, as well as steel and glass fibers, are used to investigate the effect of mortar age on the TRM system after 180 days. The results show that at the early age of mortars, their mechanical properties, and the bond behavior of textile-to-mortar have been increased. Another critical point to remember is that by increasing the mortar age, textile-to-mortar bond and mortar strength are decreased.

Development of a Damage Detecting Method for RC Slabs by Means of Machine Learning

Scipedia content — Mon, 21 Sep 2020 13:23:49 +0200

It is beneficial to understand damage conditions of RC structural members by non-destructive methods. In this study, K-means clustering method was applied to the AE wave data in order to develop a damage detection method. From the result of this study, the damaged area had the relatively large number of AE hits and AE energy. In addition, from the result of the K-means clustering of the power spectral density of AE waves, the data could be separated into the obviously damaged area and other areas.

A Maintenance Management Model. Upgrading and Experimentation

Scipedia content — Mon, 21 Sep 2020 13:23:43 +0200

The paper deals with the first results of the activities of BIG Building Innovative Governance srl, Academic Spin-Off and Innovative Start Up, which provides smart services for Building Maintenance and Facility Management also launching circular R&D actions in the relative reference areas. The contribution introduces some actions actually in progress geared to upgrading the Maintenance Management Model, M3, specifically aimed at managing the life cycle of buildings. The current stage of development corresponds to a TRL 4. TRL 8 is that expected by the end of 2020. Characterized by interconnectivity and scalability, the Maintenance Management Model is a dynamic, collaborative and implementable system, whose architecture consists of three separated but strongly interconnected devices: an information interface system, a collaborative platform, a remote cloud. An ICT network infrastructure able to activate using BIM models (IFC and COBie standards) circular information workflows between all operators and/or users involved in Maintenance and Facility Management processes. It allows the development and/or implementation of information management and sharing models based on Open Data and Semantic Web. Its use will also promote shared lexicons and the circulation of knowledge within a holistic process of managing information from and for Maintenance. The use of BIM models and the possibility of collecting and managing a large amount of data will be oriented to the structuring of information feedback databases according to ISO 15686 guidelines. In this way, available information can be usefully transferred in life cycle assessments and service life prediction of materials and components.

Mechanical Behaviour of ETICS in Presence of Water

Scipedia content — Mon, 21 Sep 2020 13:23:36 +0200

Climate change and the request for better assets’ energy performances are forcing the construction sector towards passive or even active buildings: assets with a positive balance between energy production and consumption. Building insulations play a crucial role in reducing energy demand. One of the most used technology to insulate new and refurbished buildings are the External Thermal Insulation Composite Systems (ETICS). Despite their thermal advantages, low cost, and ease of application, these systems may have serious problems if not well designed. Cracks on the coating layer are among the most common pathologies during ETICS service life. They have been studied using a Finite Element Method (FEM) analysis on two different types of ETICS in order to understand how cracks and the mechanical characteristics of materials used in the ETICS are related. The results show that errors during ETICS installation impacts on cracks occurrence as much as the mechanical performances of some layers. The FEM analysis have been complemented by the experimental study of the mechanical behavior of the coating layer under the effect of rainwater, in order to better understand ETICS behavior over their service life.

Performance of European Wood Species in Above Ground Situations After 10 Years of Weathering: Evidence of a Positive Impact of Proper Design

Scipedia content — Mon, 21 Sep 2020 13:23:28 +0200

. Most of European native wood species used outdoors are expected to last less than 10 years if left untreated and exposed to severe environmental conditions such as high humidity and biological agents. However, the current classification of wood’s natural durability based on EN standards does not fully reflect real end-use conditions, often underestimating wood’s performance in use. In addition, the importance of design details and the role they play in enhancing service life, especially in the case of outdoor applications, is often neglected. With the aim of evaluating the positive impact of proper design on wood’s service life, large-scale experimental devices, manufactured according to different designs (water draining / trapping) from six native wood species, were installed in 2009 in two French cities benefiting from different climatic conditions (oceanic / continental). The results of the evaluation carried out after 10 years of natural weathering demonstrated that (1) significant differences in the ability to withstand decay over time exist depending on the selected design details and the climatic conditions encountered in the experimental fields; (2) high variability in the resistance of non-durable spruce and poplar wood against fungal decay was noticed for each tested design, but with an unexpected high percentage of elements performing very well; (3) the moderately durable heartwood of larch, maritime pine and Douglas fir was mostly unaffected by decay even under severe conditions of exposure to rain (decking modules), suggesting these species may have greater value for outdoor applications without any preservative biocidal treatment than previously assumed.

Non-Destructive Evaluation of Micro-Cracked SCC by Ultrasonic Waves

Scipedia content — Mon, 21 Sep 2020 13:23:21 +0200

Self-Compacting Concrete (SCC) is an effective, reliable and safer technology to cast-inplace concrete structures. However, the large amount of paste required to achieve its high flowability may increase drying shrinkage at early age, due to the undesirable effects of curing conditions, producing micro-cracking and damaging concrete members. When this happens, an evaluation of the hardened SCC is necessary and Non-destructive testing techniques (NDT) can be suitable. Among NDT, Ultrasonic pulses (US) have showed to be very useful due to its portability, easiness of application and sensitivity to changes in material microstructure, porosity and presence of defects. In order to evaluate the applicability of ultrasonic (US) waves to better understand the relations among composition, microstructure, properties, curing conditions and micro-cracking, an experimental program using transmission P- and S- waves was carried out on SCC with limestone filler (LF), microsilica (MS) and nanosilica (NS), set and hardened under different curing conditions: 10, 20 and 30 °C and 40 and 80% relative humidity. Free shrinkage and double displacement restrained slabs were tested and cracking potential due to Early Age Shrinkage was assessed. Ultrasonic transmission time and wave amplitude of the raw US signal were measured and Ultrasonic pulse velocity (UPV) and attenuation coefficient were calculated. In addition, some physical and mechanical properties of cracked and un-cracked samples were measured. The aim of this study was to compare US parameters to hardened properties of cracked and un-cracked SCC. Correlations for SCC micro-cracking based on US parameters were identified, demonstrating the potential of using transmission US P- and S- waves as an evaluation technique for micro-damaged SCC

Influence of Drying on Accelerated Carbonation Testing of Concrete

Scipedia content — Mon, 21 Sep 2020 13:23:14 +0200

The aim of this work is to better understand the influence of drying conditions and moisture content of concrete on the carbonation kinetics during accelerated tests. Cylindrical specimens of a typical concrete formulation for buildings were dried, after 28 days wet curing, under three different conditions: 80°C, 45°C and 20°C and 50% RH. The carbonation depth and the height of water absorption were measured during 70 days testing under 3% CO2, 20°C and 65% RH. The results show that there is a significant difference in the drying behavior of cylindrical specimens between the lateral cast surface and their circular free surface. But, the drying cycle before accelerated carbonation tests has more influence on the carbonation rate than the type of exposed surface

Effect of Internal Hydrophobization on the Properties of Porous, Cementitious Materials

Scipedia content — Mon, 21 Sep 2020 13:23:08 +0200

Water is one of the main factors affecting the durability of porous materials and it is one of the most common causes of their degradation. Physical phenomena such as freezing or salt crystallization, as well as the development of fungi and moulds, are caused by the presence of moisture. In wet material thermal conductivity coefficient increases and the heat loss begins to rise. Hydrophobization is one of the protecting methods of porous materials against water. Two different type of water-repellent agents were used for the internal hydrophobization. The first of them is an aqueous emulsion of silane: triethoxy(octyl)silane (OTES) and the second one is also an aqueous emulsion but the matrix is poly(dimethylsiloxane) (PDMS). The paper focuses on the use of organosilicon water repellents. The main purpose of this paper is to determinate the possibility of use organosilicon agents as admixtures to internal hydrophobization. We compared results obtained for two different silicon-based admixtures. We investigated influence of both water-repellents on basic characteristics such as: absorbability, capillary water absorption and mechanical properties of cement mortar as well as heat of hydration of cement paste.

Hygrothermal Performance Difference of Wooden Beam Embedded in an Internally Insulated Masonry Wall in 2D and 3D Models

Scipedia content — Mon, 21 Sep 2020 13:22:51 +0200

Internal insulation of masonry walls may significantly increase the decay risk of embedded wooden beams due to lower temperature and consequently lower drying potential in the existing wall. Since high moisture contents will affect the performance and service life of wood, the study of moisture-related damage problems in wooden beam-ends in internally insulated masonry walls is of great importance. In the previous studies, the numerical study of hygrothermal performance of wooden beam-ends is performed only with 2D models. In this paper, we study whether a 2D numerical model can represent accurately the 3D hygrothermal behavior of wooden beam-ends. Therefore, the difference between 2D and 3D model results of the hygrothermal performance of wooden beam-ends embedded in an internally insulated masonry wall is analyzed. The difference of temperature and relative humidity in wooden beam-end between 2D and 3D models is in general small. However, 2D hygrothermal models show much lower relative humidities and thus lower moisture risk at some locations in the wooden beam-end. We find that a 3D hygrothermal model more accurately simulates the hygrothermal behavior.

Deterioration of CLT under Humid and Dry Cyclic Climate

Scipedia content — Mon, 21 Sep 2020 13:17:58 +0200

Cross laminated timber (CLT) are composed of longitudinal layers and cross layers. And as the laminations of the adjoin layers are glued orthogonally deterioration of the laminations such as check and shake and delamination can be rather frequently come out when CLT is exposed to humid and dry cyclic climate. In Japan more than 100 CLT buildings have been constructed and the number of CLT building is increasing. In some buildings the CLT is designed as to be the exterior members and exposed to the outdoor climate. Several CLT buildings that have CLT as exterior members was investigated to make clear what was ongoing on the CLT panels exposed to outdoor climate. Remarkable check and shake, warp and delamination was observed for the CLT in some of the investigated buildings. To bring out the mechanism of the distortion of CLT under humid and dry cyclic climate and to give a solution to prevent deterioration of CLT a series of laboratory tests were conducted. The CLT panels were set in a climate chamber and exposed to a humid and dry cyclic climate. And the moisture content and the movement of the laminations of CLT were measured. The movement was affected by the species of the laminations and also by the direction of the surface, sap-side or heart-side. And the film forming type painting worked well as to prevent the deterioration and the penetrating type painting could slightly reduce the deterioration.

Monitoring the Early-Age Shrinkage Cracking of Concrete with Superabsorbent Polymers by Means of Optical Fiber (SOFO) Sensors

Scipedia content — Mon, 21 Sep 2020 13:17:51 +0200

Concrete structures are subjected to shrinkage since the moment when the water makes contact with the cement. From that moment on, depending on the concrete composition and its curing conditions, chemical, autogenous and drying shrinkage might increase the risk of early-age cracking. Once a crack is formed, it may become the preferential path for the ingress of many aggressive agents inside the structure increasing the probability of damage due to corrosion, carbonation and other mechanisms. The use of superabsorbent polymers (SAPs) has been extensively studied to reduce the shrinkage cracking risk in mortar specimens by acting as internal curing agent to mitigate autogenous shrinkage. In this paper, a commercially available SAP was investigated as shrinkage reducing agent by means of internal curing in concrete specimens. The shrinkage of the concrete was monitored for 28 days with both a demountable mechanical strain gauge (DEMEC) and optical fiber sensors (SOFO). The SAP-containing concrete showed a complete mitigation of autogenous shrinkage during 28 days of measurement, for both methods. The SOFO sensors showed the occurrence of cracks after 7 days for the reference mixture, while for the SAP containing mixture, no crack was identified during the 28 days of measurements.

Behaviors of Concrete with Recycled Clay Brick as Fine Aggregate

Scipedia content — Mon, 21 Sep 2020 13:17:44 +0200

Massive waste materials were produced by the construction and demolition industry every year. In residential constructions, clay bricks are a dominant material and they account for a large proportion of construction and demolition waste. Using crushed bricks in cement concrete is an effective way to preserve natural aggregate and to reduce construction and demolition waste. The mechanical properties, the permeability and the carbonation resistance of concrete with recycled clay brick as fine aggregate were studied in this paper. The results showed that the compressive strength, the flexural strength and the impermeability of concrete decreased with the increasing of the replacement percent of recycled clay brick. However, the permeability of concrete with the water to cement ratio of 0.35 was still at the “Low” level when the replacement percent was less than or equal to 75%. The carbonation resistance of concrete using recycled clay bricks as fine aggregate was degraded.

State of Maintenance in Relation to Property Regime, Tenancy and Uses of a Large Sample of Residential Buildings Located in the Most Vulnerable Areas of the City of Barcelona

Scipedia content — Mon, 21 Sep 2020 13:17:37 +0200

In a context of downturn of public investment after the financial crisis of 2007, an increase of social and economic inequality takes place in territories and cities. Socio-residential vulnerability is intensified in certain urban areas where processes of socioeconomic and socio-spatial regression are related with the resident population difficulties to access resources for the intervention and maintenance of an aging residential building stock that gradually decays. Mediterranean cities in Southern Europe and precisely the city of Barcelona face the added difficulty of counting with a residential built stock of mostly private property, accounting many situations of horizontal property in which each building is managed by a community of owners who are not necessary householders and users. The present study consists of an analysis of the relation between the state of maintenance of residential buildings and the property regime, tenancy and uses, based on the observation of common spaces and elements of a large sample of buildings located in the most vulnerable areas of the city of Barcelona. The provided results can contribute to foster improvements in future public rehabilitation programs and policies. Particularly according to local challenges to guarantee and promote durability of a mostly privatelyowned residential built stock that is located in areas where socioeconomic difficulties hinder the residents’ capacity to carry out rehabilitation or maintenance actions. Management of the maintenance of the residential built stock must take into account the repercussion of particularities in property regimes, tenancy and uses, especially when it refers to common spaces and elements of residential buildings.

Durability Based Service Life Estimation for Chloride Exposed Cracked and Self-Healed Concrete

Scipedia content — Mon, 21 Sep 2020 13:17:30 +0200

Chloride ingress in cracked concrete leads to rapid corrosion of embedded steel reinforcement and a decrease of the expected service life. Corrosion monitoring experiments showed that a 300 μm wide crack caused initiation of corrosion of a rebar (Ø 10 mm) with a concrete cover of 26 mm within three weeks of cyclic exposure to a 33 g/l NaCl solution. After a period of unstable corrosion activity during the first 20 weeks of exposure, corrosion propagated further at a relatively high rate (0.345 to 0.718 mm³/week). Application of a theoretical pitting model revealed that a reduction of about 50% of the rebar cross-section would occur after a period of 9 to 20 years of continuous cyclic exposure to chlorides. To avoid such rapid degradation, the use of self-healing concrete can be proposed. Introduction of macro-encapsulated polyurethane into the concrete matrix, will lead to the formation of a (partial) barrier against ingress of chlorides at the moment cracks appear. Corrosion monitoring experiments showed that the autonomous crack healing could not always prevent corrosion initiation, but caused an important reduction of the corrosion rate during the 44 weeks exposure period. The mean rate of volumetric loss of steel amounted to 0.042 mm³/week, about 15 times lower than for the untreated cracked samples. The rebars also showed no or very limited signs of corrosion after visual inspection. The simplified pitting model indicated that a 50% reduction in steel cross-section would take more than 5 times longer for samples with self-healing properties versus ordinary cracked samples.

Development of 3D Printing Technology for Geopolymers

Scipedia content — Mon, 21 Sep 2020 13:17:22 +0200

The article presents the first results of the project under the title: ‘Development of 3D printing technology for construction and facade prefabricated elements made of concrete composites and geopolymers’, grant no. POIR.04.01.04-00-0096/18, funded by the National Centre for Research and Development in Poland, within the framework of programme: ‘Smart Growth Operational Programme 2014-2020, IV Increasing the research potential, 4.1.4: ‘Application projects’. The main aim of the project is design and development of the innovative large-format printer using geopolymers for 3D printing for residential houses. It allows the development of a technology for the production of a universal residential building, with a construction that is easy to transport and fast to assemble, as well as with the possibility of simple and quick expansion depending on the needs of users. The article shows the main idea of the advanced large format 3D printing for geopolymers with using an ergonomic printing method as well as materials research in modern filaments in the form of geopolymers.

Concrete Durability Probed Using Compressive Strength, Chloride Penetration and Porosity Measurements on CEMII and CEMV Concretes Incorporating Mollusc Shell Spares in Artificial and Natural Seawaters

Scipedia content — Mon, 21 Sep 2020 13:17:15 +0200

The purpose of this study is to improve the recruitment of flat oyster larvae, an endangered species, by means of a specific marine infrastructure made of concrete. This work aims to develop and optimize concrete formulations by varying the type of cement and introducing shellfish by-products into their composition and determine which concrete formulation is the most sustainable to marine organism colonization. Indeed, it is essential to obtain a sustainable concrete submitted to aggressive marine environment (chloride ions diffusion and bio-colonisation). Four concrete formulations were tested with two types of cements (CEMII and CEMV) and with or without the incorporation of shell aggregates. The durability of these materials was tested after 3 months of immersion in the Rance of Dinard (France). It appears from this study that the CEMII concrete exhibits a good mechanical resistance independently of the presence of shell, after immersion in situ. This concrete also shows better resistance to chloride ions diffusion than CEMV. However, CEMV possess larger compressive strengths than CEMII, and mollusc shells incorporation does not decrease this strength as much as for CEMII. Shell incorporation in the concretes has an effect on strength, chloride penetration and porosity which depend on the used cement and seawater.

Effect of Carbonation in Mortars with Different Types of Metakaolin and Curing Procedures

Scipedia content — Mon, 21 Sep 2020 13:17:08 +0200

This study aimed to evaluate the influence of different types of metakaolin and curing conditions on mortars depth of carbonation. To do so, prismatic mortar specimens were produced by using three different 1:2 mix proportions (binder: sand): a reference mix proportion (without mineral addition) and two mixes with partial replacement of the cement by metakaolin, in the content of 10% by mass of cement. Two types of metakaolin with different characteristics were used in order to verify their capacity of changing the mortar microstructure and the pore solution, modifying this way the carbonation behavior of these materials. Three curing conditions for the test specimens were defined: no wet curing and wet curing (by immersion in water) for 3, 9 and 28 days. After the accelerated carbonation procedure in a CO2 chamber (in an atmosphere of 10% of CO2), with a relative humidity of 70% and a temperature of 20°C, for a period of 7 days, the carbonation depth was measured by using pH-indicators based on phenolphthalein and thymolphthalein. The results indicated influence of the type of curing in the carbonated depth and the significant interaction between curing and the type of metakaolin. When wet curing was not performed, the carbonation was more intense in the reference mortar. The effect of curing in the mortars with metakaolin was much less significant compared to that in the reference mortar. A global discussion about carbonation behavior of metakaolin modified mortars will be performed, based on the characteristics of the metakaolins.

Influence of the Particle Size Distribution of Natural Sands in the Accelerated Alkali-Silica Expansion Test (AMBT)

Scipedia content — Mon, 21 Sep 2020 13:16:59 +0200

The accelerated mortar bar test (AMBT) is used to evaluate the potential expansion of the aggregate for the alkali-silica reaction. In this test, the aggregate should meet a certain distribution of particle size. In Uruguay it is usual that for concrete the fine aggregate is constituted by a mixture of sands, one of coarse size and another of fine size. Therefore, coarse sand must be crushed for the test and the fine sand is weighted accumulated in the smallest sieve in which there is enough material according to its particle size distribution. The aim of the work is to evaluate the influence of the particle size distribution of natural coarse sands, without crushing, in the result of the AMBT test. Mortars with different grading composition and single particle size were elaborated, and the differences obtained in the expansion, in the formation of efflorescence on the surface of the bars and in the presence of the reaction gel in the solution where the bars were immersed were analyzed. A greater expansion was observed in the samples with a continuous size distribution, compared with a single particle size. In addition, in the bars elaborated with the largest particle size, a greater amount of gel on its surface and in the solution was observed. The relevance of the work was to improve the reliability of the result in the AMBT test to evaluate the reactivity of the natural coarse sand. Natural sands of siliceous quartzfeldespathic origin were evaluated, without pessimum effect.

Behavior of Waterproofing Systems Exposed to Environmental Agents

Scipedia content — Mon, 21 Sep 2020 13:16:52 +0200

The service life of buildings can be associated with the durability of enveloping the elements, e.g., the flat roofs that are constantly exposed to environmental agents. Waterproof membranes, produced with bituminous or polymeric materials, usually protect these elements. This paper presents an experimental study of waterproofing systems subjected to environmental agents of degradation. Four types of membranes were tested: bituminous, polyurethane, acrylic and acrylic with polyester mesh. All membranes were applied to concrete substrates and exposed to cycles of 48 hours in 70°C oven and 24 hours in immersion vats with 23°C water. The specimens were subjected to 0, 4, or 8 cycles and submitted to pull-off tests. The results demonstrated that the waterproof system behavior change when subjected to cycles of the temperature gradient. The tests show that the different thermal deformation between the membranes and the concrete substrate results in loss of adhesion.

Evaluation of the Effects of Environmental Exposure on the Performance Decay of ETICS

Scipedia content — Mon, 21 Sep 2020 13:16:42 +0200

The performance decay of a building component is influenced by a huge variety of parameters, interacting between them and determining different results in terms of service life and performance over time. For this reason, evaluating and modeling the performance of a component requires the comprehension of the way and the measure the single factors affect it, and turning this into an analytical model is a very complex operation. Moreover, components of existing buildings are subjected to an additional incognita: the characteristics and the durability of the materials, which is hardly a certain information, and can vary between similar buildings, affecting the accuracy of the evaluation. This study, conducted according to the guidelines of ISO 15686:7 code, investigates on a common solution for interventions on existing buildings, the ETICS, surveying their current performance degree through thermographic camera tests. The aim is to appreciate the difference in the performance decay between different façades of the same building - a homogeneity that allows to estimate this parameter alone - in order to reach an analytical expression of the variation of performance decay according to the difference in the exposure. The sample is constituted by buildings of large dimensions and well-known original projects and details of successive interventions, located in the city of Naples. The data obtained with in-field measurements were subjected to statistical analysis, to allow the quantitative determination of the impact of this parameter.

Durability of Internally Insulated Historical Solid Masonry Under Future Climates: A Stochastic Approach

Scipedia content — Mon, 21 Sep 2020 13:16:35 +0200

Today, it is globally known that climate change needs to be addressed to mitigate its harmful effects on our environment. It is also common knowledge that the contribution of historical buildings to the energy consumption of the existing Canadian building stock is severe. Buildings of historical identity are often poorly thermally insulated. Thus, to increase energy efficiency and occupant comfort in cold climates, the application of thermal insulation on the interior side of solid masonry walls offers a possibility to improve the historic buildings’ energy performance, without compromising their identity and cultural heritage values. As a result, the historical masonry will be subjected to lower temperature during the heating season, which can increase the potential for condensation and frost within the wall. A balance must therefore be reached between durability measures and thermal performance objectives. This paper intends to achieve this balance through determining the impact of the interior insulation thickness on the durability of a typical historical masonry wall under the effect of climate change. A stochastic approach is used in hygrothermal simulations to account for the uncertainty in material properties. Results in Ottawa indicate a higher risk to frost damage after interior insulation is added to a brick wall having a moisture critical degree of saturation (Scrit) of 0.25 and 0.35. Moreover, both deterministic and the stochastic results were in good agreement. Also, both methods showed an increase risk to frost damage under a changing climate.

The Stone Masonry Contribution in Greek Industrial Buildings’ Typology and Construction Durability (Late 19th to Early 20th Century)

Scipedia content — Mon, 21 Sep 2020 13:16:28 +0200

Stone masonry is the oldest form of construction in the world until the beginning of the 20th century. The first stone walls were constructed by farmers and primitive people by piling loose field stones into a dry stone wall. Later, mortar and plaster were used, especially in the construction of city walls, castles, and other fortifications before and during the Middle Ages. These stone walls are spread throughout the world in different forms. Stone walls are usually made of local materials varying from limestone and flint to granite and sandstone. However, the quality of building stone varies greatly, both in its endurance to weathering, resistance to water penetration and in its ability to be worked into regular shapes before construction. Also, the majority of buildings in Greece at the end of 19th century up to the use of concrete in constructions are load-bearing stone masonry structures. Moreover, research shows that it is the most widely construction material in industrial buildings, that era. As it is known, stone masonry has high compression strength under vertical loads but has low tensile strength (against twisting or stretching) unless reinforced, while the tensile strength of masonry walls can be increased by thickening the wall. In general, industrial buildings constructed of stone masonry, from late 19th to early 20th century, have particularities in their typology because they were directly dependent on their mechanical equipment and production line. The aim of this study is to investigate the contribution of stone masonry as a construction material in the typology of these industrial buildings concerning their durability.

On the Effects of Relative Humidity and CO2 Concentration on Carbonation of Cement Pastes

Scipedia content — Mon, 21 Sep 2020 13:16:21 +0200

Many environments to which concrete is exposed are highly aggressive due to various chemical components. In such environments, concrete is subjected to processes of chemical degradation, among which carbonation is one of the most frequently seen degradation processes. Though, the influence of saturation degree (or relative humidity - RH) of the specimen and CO2 concentration on the carbonation of cementitious materials is still not comprehensively described with respect to carbonation rate/degree as well as alteration in microstructure and mineralogy. This work aims at thoroughly investigating how these two key parameters affect the carbonation under accelerated conditions. Furthermore, the effect of initial moisture state of the specimen on the carbonation rate is also demonstrated. For such purpose, a numerical model at continuum scale is developed to investigate the effects of RH and CO2 concentration on the carbonation depth, phase changes in phases and porosity of hardened cement pastes due to carbonation under accelerated conditions. Verification with experimental results from accelerated carbonation tests shows a good agreement. The modelling results with supporting experimental data help to better understand the modification of material properties under different carbonation conditions and to optimize the carbonation conditions.

Metamodel Development for Predicting Hygrothermal Performance of Wood-Frame Wall under Rain Leakage

Scipedia content — Mon, 21 Sep 2020 13:16:14 +0200

In recent years, stochastic modeling has been increasingly applied to investigate the uncertainties of input parameters in hygrothermal simulation and the moisture damage risks of building envelopes. Generally, stochastic modeling requires hundreds or even thousands of simulations to take into account the uncertainties of input parameters, which is computationally intensive and timeconsuming. This paper aims to apply polynomial and neural network metamodel as a substitute for the traditional hygrothermal model, to predict the hygrothermal performance of building envelopes. In the previous study carried out by the authors, stochastic simulations have been performed based on the traditional hygrothermal model, to investigate the hygrothermal performance of wood-frame walls under different rain leakage levels. The material properties and rain deposition factors were considered as stochastic variables, and stochastic simulations were performed under three rain leakage scenarios: 1%, 0.5% and 0.1% of wind-driven rain. In this paper, the stochastic inputs (the hygric material properties and rain deposition factor) and outputs (the maximum moisture content and mold growth index over a 5-year period of the simulation) of a conventional 2×6 wood-frame wall are used to develop the metamodels through polynomial regression and neural network methods. The metamodels are developed for each rain leakage scenario, and the stochastic data of the three rain leakage scenarios are aggregated together to train another metamodel. It is found that the metamodels generally perform well to predict the maximum moisture content and mold growth index. The metamodels for low rain leakage scenarios are better than those for high rain leakage scenarios and the neural network metamodel is more accurate than polynomial metamodel for high rain leakage scenarios, i.e. 1% of rain leakage.

Influence of Surface Treatment of Fresh Concrete on its Resistance to Drying Shrinkage

Scipedia content — Mon, 21 Sep 2020 13:16:07 +0200

The volume changes of cement-based composites are significantly exhibited during the hardening process. Initial phases of the hardening are complemented by the expansion due to the heat evolution that is subsequently alternated by the shrinkage. Both could cause the crack initiation causing significant loss of the durability and service-life shortage. The present paper focuses on the experimental investigation of the surface treatment of fresh concrete, which is applied to prevent sudden loss of the moisture during a hardening process, especially during the concrete highway construction. The technology of concrete highway production is extremely costs demanding, but its efficiency is determined by the longer lifespan in comparison with the asphalt pavement. However, negative impacts of the drying shrinkage could significantly reduce the durability. The efficiency of used treatment was investigated in terms of restrained shrinkage tests, water adsorption and mechanical testing. In addition, there were studied two types of conventional Portland cement. Performed program confirmed great sense of the curing on the concrete durability; in addition, there was well illustrated the efficiency of the utilization of blended binder systems in the paper.

Pathologies of a Glass Building Envelope that Affect Durability and Comfort

Scipedia content — Mon, 21 Sep 2020 13:16:00 +0200

The durability of materials used in buildings has been widely studied and, in many cases, there are standards to assess it. However, studies on how pathologies affect the durability and comfort of the building users are not so common. The aim of this article is to explain different pathologies of the building envelope, considering glass as its main element and to analyze the causes of those pathologies, agents involved, and how they have affected durability. For that purpose, different cases of pathologies were analyzed on-site, both during the construction process and during the final use of the building. The effects of the different pathologies were also assessed. In each case, the technical data sheets available of the materials involved and the information on the design and the expected performance of the constructive solution were compiled. In some cases, the pathologies had caused an irreversible damage, so, the solution had to be drastic; while in other cases, they were detected early enough to propose remedial actions without affecting the final durability of the building. After having analyzed the different cases, the agents causing the pathology or those responsible for it and the phase in which the pathology occurred were identified. As a result, remedial actions were proposed to avoid the generation of pathologies during the design, construction and maintenance processes that affect the durability of the building and their user‘s comfort.

Dynamic Observability Method for Durability Assessment Considering Measurement Noise

Scipedia content — Mon, 21 Sep 2020 13:15:54 +0200

Due to the inevitable degradation of material properties in structures in daily use, such as stiffness degradation due to cracking in concrete elements, their durability will definitely be influenced, and their serviceability and safety could be in danger. Thus, understanding and identifying the change in the structural parameters provides new approaches to evaluate their durability. Structural system identification by dynamic observability method, which is using subsets of masses, natural frequencies and modal shapes, is a powerful tool to detect the change of structural parameters. Taking into account the presence of noise in the measurement data in real world structures, this method establishes the relative dynamic equation with the error separation items. The equation is solved by error minimization of an objective function combining the measured frequencies and mode shapes through the parameter MAC (Modal Assurance Criterion). Additionally, the algorithms and the steps are introduced based on the dynamic eigenvalue equation, which can fully demonstrate the performance of observability techniques. The present paper provides an example on how to successfully identify structural parameters. Its suitability for practical applications is demonstrated in a large frame structure. The result is a much more accurate identification of the parameters involved in the durability of the structure even in the case of noise-corrupted measurement signals.

Methodology for Predicting the Service Life of Two-Ply Roofing-Felt Membrane

Scipedia content — Mon, 21 Sep 2020 13:15:47 +0200

The service life of roofs depends not only on the quality of materials and components but also on several other factors such as workmanship, maintenance, design and substrate. The service life of materials is at production time estimated to a certain number of years. Later when some experience has been gained the service life can hopefully be better predicted. However, the predicted service life can always be questioned because no one knows how long the product or material will last. The durability of a two-layer roofing-felt membrane has been investigated through inspection of several 20 to 30 years old roofs that had aged naturally under in use conditions in a northern humid climate. In 50 % of the inspected roofs, samples were taken out for laboratory test. In this paper, the developed methodology to conduct a service life prediction of roofing membrane is presented. The paper includes a description of the on-site inspection; test conducted in the laboratory which was used as basis for predicting the service life of the two-layer roofing-felt membrane and how these information are extrapolated to a predicted service life. Further, it is discussed if the used methodology for prediction is generally applicable for other types of membranes.

Resistivity Measurements to Assess the Freeze - Thaw Attack on Concrete - Lab Specimen and Real Structure

Scipedia content — Mon, 21 Sep 2020 13:15:41 +0200

Waterway structures like locks are exposed to a severe freeze-thaw-attack. A sufficient resistance of concrete against this exposure has to be assured. In Germany the concrete for the exposure class XF3 of federal waterway structures has to be tested in the laboratory by the CIF-Test in addition to descriptive requirements. To establish this procedure experiences on concrete mix designs which have been applied in the past were considered as well as research concerning the transferability of laboratory tests to practical experience. One important aspect was a service life study on the degree of water saturation of the concrete under practical conditions in combination with the temperature exposure. The paper presents the results of freeze-thaw tests on lab specimens and cores of concrete elements stored differently and tested at different ages. For a better understanding of the processes of the freeze-thaw attack during the freeze-thaw tests monitoring data of resistivity has been analyzed and compared to hardened concrete properties. The water absorption inside the specimen during capillary suction and the freeze-thaw-cycles could be monitored at different distances to the surface. Correlations of the water absorption to the initiation and development of internal damage were observable. A consideration of the results of the freeze-thaw tests and the resistivity measurements enables a better evaluation of long-term resistivity monitoring data of a lock. It allows for an assessment of the transferability of results of the CIF-Test to practical experience.