Scipedia: Documents published in 2023

Flexibility and Adaptability: A Review on Assessment Methods and Tools and Their Applicability

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:57:13 +0200

In this paper, the existing methods for the assessment of flexibility and adaptability in buildings are reviewed. These methods have been tentatively proposed for a number of building types / uses - notably for residential buildings - and generally propose sets of indicators, variables and weights that combine into a score of flexibility. In spite of the limited practical applicability of these methods so far, they provide a stimulating approach to greater use and incorporation of the concepts and strategies of flexibility and adaptability, aiming at an increased performance of buildings.

Durability and Long-term Performance Assessment in Eco-efficient Concrete Mixtures Towards a More Sustainable Cement Industry - A Critical Review

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:56:59 +0200

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

Changes in Educational Buildings at Very Early Stages of Their Life Cycle

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:56:45 +0200

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

Analysis of the Repassivation of Corroded Bars in Cementitious Materials Subjected to Realkalisation

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:56:30 +0200

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

Durability Assessment and Maintenance Planning of Concrete Structures in Ningbo-Zhoushan Port Main Channel Sea Link Project

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:56:18 +0200

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

Damaged Swedish Buildings

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:56:02 +0200

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

Classification Systems for the Built Environment: A Cornerstone for the Long-term Performance Analysis

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:55:46 +0200

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

Causes of Damages in Swedish Buildings

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:36:38 +0200

Damages, failures and functional defects in buildings create high cost for the owner and the society. It is important to determinate the causes of damages in order to limit the costs. This paper presents the causes of 1105 different damages from a technical perspective from 265 real damage investigations. In general, the results show that; 1. Rain and snow was the most common moisture source cause damages, 2. The number of damages caused by wet concrete and PVC or linoleum flooring may be overestimated. 3. A significant number of damages were caused in details where different materials connect to each other, 4. A high number of damages were linked to wear and tear and poor maintenance. 5. Causes of damages occurs in all phases of the building process but most of them were deemed to occur in the management and on-site construction phase. 6. Most of the damages were caused by building owner or their facility trustees.

Assessment of the Impressed Current Cathodic Protection System after 4 Years Operation: Evolution Over Temperature and Time of the Applied Current and Tension on Anodic Zones of the Saint-Cloud Viaduct (France)

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:35:40 +0200

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

Analytical and Experimental Service Life Assessment of Ningbo-Zhoushan Port Main Channel Sea Link Project

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:34:36 +0200

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

An In-situ Method for Assessing the Kinetics of Acid Attack on Iron-richAlkali-activated Materials

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:33:39 +0200

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

Experimental Study of the Development of Stresses in Prestressing Strandsunder Different Environments

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:32:36 +0200

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

Exploring Moisture Performance of Two Distinctive Solid Bricks underCurrent and Future Climate in London

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:31:38 +0200

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

Freeze-thaw Damage Mechanism and Cracking Behaviour of PerforatedPlateau Concrete Structure

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:30:37 +0200

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

Hygrothermal Performance of CLT Subjected to Rain Loads duringConstruction in Belgium

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:29:39 +0200

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

Numerical Simulation on the Pouring Process of Self-compacting Concretein CRTS III Slab Track

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:28:37 +0200

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

Modeling the Sulfate-induced Damage of Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:27:55 +0200

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

MARS – A Multiphysics Framework for the Analysis of Cast and PrintedConcrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:27:36 +0200

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

Effects of Surface Layer on Moisture Transport in Cementitious Materials:Experimental Evidence and Simulation Results

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:27:22 +0200

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

Degradation Behavior of GO-ternary Blended Nano-concrete Compositesunder Accelerated Sulfuric Acid Attack

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:27:06 +0200

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

An Experimental and Numerical Study of the Effect of Heat and ThermalShock in Precast Concrete Wall System

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:26:49 +0200

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

Effect of Repeated Loading on the Flexural Load Carrying Capacity ofMarine Concrete Beams Exposed to Chloride Environment

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:26:32 +0200

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

Monitoring Steel Rebar Corrosion-induced Cracking in ECC Cover byDOFS

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:19:08 +0200

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

Evaluation of Alteration in Cement Paste Due to Calcium Leaching withIntegrated CT-XRD Method and Its Effect on Ionic Diffusions

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:18:51 +0200

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

Evaluating the Corrosion Level of Bare Steel Bars with Pitting Corrosionby DOFS

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:18:35 +0200

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

Research on the Corrosion Behavior and Cathodic Protection of Defected-Epoxy-coated Reinforcement Exposed to Chloride Environment

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:18:25 +0200

The application of epoxy coated rebar (ECR) is an effective method to improve the durability of reinforcement in chloride environment. However, the coating defects caused in construction will significantly decrease its corrosion resistance to chloride. Herein, the corrosion behaviors of different defects rate in ECR under chloride attack in South China are investigated. The results indicate that the corrosion of ECR is due to the coating defects, the corrosion potentials of defected-ECR are shifted to negative, and the corrosion current density is significantly increased with increasing the defect rate. The corrosion resistance of defected-ECR is improved by applying the anode-mortar cathodic protection system, both the exposure test and engineering application all show that the durability of defected-ECR is increased with the high polarization potential (≥ 200mV) and negative protection potential (＜-800 mV).

Hygrothermal Behaviour of Non-traditional Mortars and ConcretesEva Barreira1, Ricardo M.S.F. Almeida1,2 and Margarida Pais

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:18:13 +0200

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

Experimental Study on Macro-performance of Long-age HydraulicConcrete Based on High Temperature Accelerated Curing

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:17:52 +0200

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

Evaluating the Energy and Mechanical Properties of CSH/nano-CC Interface: An Atomic Investigation

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:17:38 +0200

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

Damage Process Assessment of Mortar Samples under Freeze-thaw Cycleswith Micro-CT and Expansion Measurements

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:17:21 +0200

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

The impact of crises on the sustainable development of regions: foreign empirical evidence

Elisaveta Grebennikova — Tue, 03 Oct 2023 11:17:03 +0200

The current frequency of crises and the increasing risks to the sustainable development of regions around the world create a need for significant research on this issue. The relevance of the proposed work lies in the high degree of importance of the concept of sustainable development for Russia and the entire world community. The scientific novelty of the study lies in the presentation of the most detailed analysis of current foreign studies on the impact of crisis phenomena on the sustainable development of regions - at the same time, various crises are considered, including the global financial crisis of 2008, the COVID19 pandemic, as well as natural disasters, humanitarian disasters, etc. In addition, a wide range of aspects of sustainable development are presented, which are subject to the influence of crisis phenomena. The purpose of this literature review is to present a wide range of approaches to managing risks to the sustainable development of regions caused by crisis phenomena. At the same time, the tasks set are to study the very concept of a crisis, analyze the theoretical approaches of schools of regional development, study aspects of sustainable development, as well as identify the impact of crisis phenomena on the sustainable development of regions and present sustainable regional strategies to combat crisis phenomena. The main research method is literature analysis. Based on the results of the work, it was concluded that in foreign literature the impact of crises on regional sustainable development is considered from different perspectives. When analyzing one specific case, it is important to take into account the following variables: the scale of the crisis (local, global), the nature of the crisis (economic, political, environmental, social), the resilience of the region to the crisis, cultural and historical factors, social capital. Sustainable regional development is one of the processes that are affected by the crisis associated with the environmental, social, economic and even political component.

Sensitivity of Capillary Absorption and Sorptivity to Water Retention, Permeability and Other Relevant Characteristics for Cement Mortars

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:17:03 +0200

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

Application of Ultrasonic Computerized Tomography Technique to Detect the Internal Defects in Cement-based Mortar

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:16:39 +0200

It is widely acknowledged that ultrasonic technology provides a considerable detection approach while describing the internal fractures in concrete, which is a serious issue when evaluating the durability performance of cement-based materials. This paper aims to introduce the work which is concerned with the use of ultrasonic computerized tomography (UCT) technique to evaluate the micro-cracks inside mortar. The result shows that UCT is a relatively promising method which is capable of imaging the positions of tiny cracks and local damage, moreover, the application of X-ray computerized tomography (XCT) also verifies the accuracy and reliability of UCT. Effective evaluating the internal cracks depends on the detection of attenuation of ultrasonic signals that perpendicular to internal cracks, furthermore, ultrasonic technology is more likely to detect the crack with larger surface of damage, but not sensitive to local fracture.

Experimental Evaluation of Flexural Strength and Ductility of One-Way Concrete Slab Panels Reinforced with Welded Wires and Deformed Bars

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:16:22 +0200

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

Pitfalls in Using Electrical Conductivity to Monitor the Chloride Ingress of Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:16:05 +0200

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

Corrosion Mechanisms of Reinforced Alkali-Activated Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:15:52 +0200

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

Effect of Moisture History on ASR Expansion and Microstructural Properties

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:15:34 +0200

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

Comparison Between Parameters of Corrosion, Obtained by Destructive and Non-destructive Electrochemical Techniques

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:15:20 +0200

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

Durability of Concrete and Reinforced Concrete Structures Subjected to Temperature Cycles: Insight from Multiscale Thermomechanical Analysis

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:00:26 +0200

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

Influence of Coarse Aggregate Grade on Air Void Structure of Air-entrained Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:00:15 +0200

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

Efficiency Evaluation of Metakaolins for Use in Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 11:00:03 +0200

The use of metakaolins has been shown to be effective in modifying the properties of cementitious materials related to durability, highlighting the very positive impact in terms of increasing the electrical resistivity of concrete and reducing ionic transport in this porous medium. In this sense, the present work aims to evaluate the efficiency of different metakaolins in terms of pozzolanic activity, linking the efficiency to various characteristics of the metakaolin. Five samples of different Brazilian commercial metakaolins were then characterized, using the following methods: BET specific surface area, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, thermal analysis (TA/DTA), thermogravimetric analysis (TG/DTG) and determination of pozzolanic activity by the modified Chapèlle method. As the main results, it was found that the BET specific surface area and the Al2O3 content, obtained by XRF, better explain the pozzolanic activity of metakaolins (Pearson correlation coefficients equal to 0.89 and 0.94, respectively). The amorphous content (quantified by Rietveld in the XRD) showed only a reasonable correlation with the pozzolanic activity determined by the modified Chapèlle method. In general, the chemical-mineralogical characteristics that indicate purity and amorphism of metakaolin, expressed by the Al2O3 content, Al2O3/SiO2 ratio, SiO2+Al2O3 sum, and amorphous content, represent important performance parameters of metakaolins. The specific surface area compensates for lower purity or chemical reactivity and significantly influences pozzolanic activity.

Reinforced Concretes of Tomorrow: Corrosion Behaviour according to Exposure Classes

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:59:28 +0200

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

Hydrophobicity Mechanism of Cementitious Material Containing Carboxylic Acid Ammonium

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:59:05 +0200

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

Accelerated Degradation of Coating-mortar Interface under UV Radiation in Presence of Water

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:58:53 +0200

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

Accelerating Effect of Heating Treatment on the Damage of Cement Paste under Sulfate Attack

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:58:36 +0200

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

Degradation of Cement Pastes Subjected to Combined Carbonation and Leaching

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:58:21 +0200

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

Cement Degradation Caused Risks for Geological Carbon Sequestration Reservoirs

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:58:09 +0200

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

Durability of GFRP and BFRP Bars in Sulfoaluminate Cement Concrete Made with Seawater and Sea Sand

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:57:59 +0200

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

Study of the Chemical Processes of Combined Sulfate-chloride Attack on Low-carbon Cementitious Materials

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:57:44 +0200

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

Mineralogical Characterization of the Biodegradation of Sewage Cementitious Materials in the Presence of H2S

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:57:26 +0200

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

Hysteretic and Scanning Behaviors of Water Vapor Sorption in Hardened Cement Pastes

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:57:12 +0200

Water in the multiscale porous microstructure of cement-based materials is closely related to multiple deterioration processes, hence significantly influences the durability of concrete structures in atmospheric environment. Water vapor sorption is the key tool for characterizing the hygroscopic properties of cement-based materials, also a promising technique for exploring their nanopore structures. The significant hysteresis between different sorption branches is stemmed from the complexity of interconnecting pore system and concurrence of different physical phenomena. In this study, the hysteretic and scanning behaviors of water vapor sorption in hardened cement pastes are measured with a dynamic vapor sorption instrument, and investigated to provide new insights into the path-dependency of sorption behaviors on humidity history and resolve the overall sorption hysteresis into contributions from different phenomena.

Effect of Electric Field on the Degradation Process of Reinforced Mortar under Chloride and Sulfate Attack

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:56:54 +0200

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

Dissolution Behaviour of Alkali-activated Fe-rich Non-ferrous Metallurgy Slag in Acetic Acid

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:56:35 +0200

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

Thermal-Resistivity Characteristics of Carbon Fabric Reinforced Cementitious Matrix

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:56:19 +0200

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

Study on Shrinkage Properties of Repairing Mortar Modified by Basalt Fiber

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:38:34 +0200

In order to study the shrinkage properties of modified repairing mortar, an orthogonal experiment with four factors and three levels were proceeded. Nine specimens with four factors, i.e., silica powder, sodium silicate, basalt fiber and a U-type expansive agent, were used to measure the length change ratio. The results show that the shrinkage value of modified repairing mortars have been greatly reduced. Compared with the control specimen without any additives, the shrinkage value of the modified repairing mortar with the silica powder of 3 %, the sodium silicate of 1.0 %, the basalt fiber of 0.2 % and the U-type expansive agent of 10 % at 60d drops by 42.5%. Based on experimental results, the shrinkage prediction model of modified repairing mortar has been established. The model can be used to predict the shrinkage value of the modified repairing mortar with similar compositions.

Experimental Study on Improvement of Interfacial Bond Properties of Carbon Fiber Reinforced Cement Matrix Composites by Nano Silica

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:38:17 +0200

The fiber reinforcement efficiency of carbon fiber reinforced cement matrix composites (CFRCM) is limited by the low permeability of mortar to internal filaments in the fibers, leading to premature failure of the composites due to low bond strength. In this paper, three kinds of nano-silica materials were used to improve the bond properties of carbon fiber bundles to cement-based matrix by coating and electrophoretic deposition. It is found that different methods have different positive or negative effects on the improvement of bond properties, and the effects are different under different embedded lengths. The modification principle is due to the high impregnation of nano silica particles on the fibers and the reaction of volcanic ash of the particles, which promotes the formation of calcium silicate hydrate gel inside the fibers. Relevant research needs further exploration.

Electrical Joule Heating and Early Strength of Mineral-impregnated Carbon Fibre Reinforcement (MCF)

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:37:57 +0200

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

Developing Multifunctional Ultra-High Performance Concrete via Incorporating Hybrid Steel Wires and Fibers

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:37:37 +0200

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

Study on Performance of Negative Temperature and High Strength Bed Mortar Material for Wind Power Engineering

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:37:19 +0200

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

Effect of Alkali-free Accelerator Containing Nano-silica on the Durability of Shotcrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:36:37 +0200

The effect of nano-silica-containing alkali-free accelerator and ordinary alkali-free accelerator on the durability of C30 shotcrete was investigated by means of seepage resistance tests and frost resistance tests. The results show that under the same conditions, the C30 shotcrete with nanosilica-containing alkali-free accelerator has a lower electrical flux and a greater impermeability rating than P10. The C30 shotcrete with nano-silica-containing alkali-free accelerator maintains a mass loss rate of about 0.4% after 200 freeze-thaw cycles, a 10.5% decrease in relative dynamic modulus of elasticity, a compressive strength loss rate of less than 20%, the bubble spacing coefficient and the average bubble diameter increased by 20.9% and 60.5% respectively, showing good frost resistance performance. This indicates that alkali-free accelerator containing nano-silica can improve the durability of shotcrete. In addition, a comparison was also made between ordinary accelerator shotcrete with nano-silica, and when 5% nano-silica was added, the properties of shotcrete were comparable to those of 2% nano-silica alkali-free accelerator shotcrete.

Combining Wood Protection Options to Enhance Resistance against Decay and Improve Fire Safety of Engineered Wood Products like CLT

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:35:40 +0200

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

Capacity of Wood as Flooring Material: Improvement of Thermal Performance of Wood/Phase Change Material Composites

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:34:40 +0200

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

Transforming low-quality sand into construction materials under 110℃ and Recycling of the Waste Solution

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:33:34 +0200

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

Recycling of Silty Waste Soil by CO2 Treatment for Construction Block Manufacture

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:33:23 +0200

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

Partial Replacement of Fly Ash & Modified Bottom Ash as a Cement & Fine Aggregates in Concrete

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:33:09 +0200

This study envisaged the application of Bottom ash as a replacement of fine aggregate. In this study, bottom ash is thoroughly mixed with a PC-based High range superplasticizer ( HRSP) having solid content more than 60%, this sand is called as modified bottom ash (MBA are mixed at doses of 0%, 0.25%, 0.5%, 0.75%, and 1% by weight of bottom ash. This prepared bottom ash is referred to as modified bottom ash (MBA). MBA is substituted for fine aggregates in ordinary concrete in varying amounts from 0 to 50% by river sand and the concrete has been tested for Compressive strength, flexural strength, split tensile strength, and other durability characteristics it has been found that 10% MBA produce superior outcomes, the purpose of use was not achieved. Therefore, MBA has been increased up to 60% replacement with fine aggregates, the strength and durability properties achieved for concrete produced by 50% MBA with fine aggregate (sand) are compared to 100% fine aggregate (sand) concrete and has observed similar results due to addition of HRSP. In the end, it can be concluded that High Range Superplasticizer HRSP is quite efficient for replacing Bottom ash with fine particles.

Durable Textile-reinforced Concrete Made of Fast-setting, Mineralimpregnated Carbon-fibers (MCF) Reinforcements and Alkaline-activated Matrix

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:32:43 +0200

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

Durable Structural Concrete Using Fine and Coarse Recycled Aggregates (Type A and Type B)

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:32:22 +0200

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

Carbon Neutral Concrete – Challenges and Solutions for Sustainable Future

Jesús Sánchez Pinedo — Tue, 03 Oct 2023 10:32:07 +0200

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

Revista Latinoamericana de Ginecología Regenerativa. Volumen 1, número 2

Luis Traviezo — Tue, 03 Oct 2023 08:52:02 +0200

Misión

La Revista Latinoamericana de Ginecología Regenerativa tiene la misión el generar, discutir y difundir investigaciones, conocimientos, documentos y demás información en Ginecología Regenerativa y áreas afines, para que esté al alcance de profesionales y estudiantes de las Ciencias de la Salud y del público en general, a través de un planteamiento práctico, sencillo y atractivo, que permita llegar a un mayor número de usuarios, lo que servirá para la divulgación científica en salud.

Visión

Ser una revista reconocida tanto nacional como internacionalmente, que sea un punto de referencias en Ginecología y motivo de consulta constante de profesionales del área, logrando la inclusión en índices tanto nacionales como internacionales, fruto de un reconocimiento por cumplir con los estándares bibliométricos y cienciométricos nacionales e internacionales.

Objetivo General

Publicar artículos de investigación, artículos históricos, imágenes en Ginecología Regenerativa y cartas al Editor, que versen sobre la Ginecología Regenerativa, especialmente sobre temas como la Ginecología Estética, Ginecología Funcional, Bioestimulantes en Ginecología, Energía en Ginecología, Complejo Clitorolabial, Labios Mayores, Vagina, Ano, Manejo de Complicaciones, Dilemas Éticos, Mercadeo y Redes Sociales en Ginecología y demás temas relacionados con la Ginecología Regenerativa.

Revista Latinoamericana de Ginecología Regenerativa. Volumen 1, número 1

Luis Traviezo — Tue, 03 Oct 2023 08:44:02 +0200

Mission

The mission of the Latin American Journal of Regenerative Gynecology is to generate, discuss and disseminate research, knowledge, documents and other information on Regenerative Gynecology and related areas, so that it is available to professionals and students of Health Sciences and the general public, through a practical, simple and attractive approach, which allows reaching a greater number of users, which will serve for scientific dissemination in health.

Vision

To be a nationally and internationally recognized journal, which is a point of reference in Gynecology and a reason for constant consultation by professionals in the area, achieving inclusion in both national and international indices, the result of recognition for complying with national bibliometric and scient metric standards, how international.

General objective

Publish research articles, historical articles, images in Regenerative Gynecology and letters to the Editor, which deal with Regenerative Gynecology, especially on topics such as Aesthetic Gynecology, Functional Gynecology, Biostimulants in Gynecology, Energy in Gynecology, Clitorolabial Complex, Labia Majora, Vagina, Anus, Management of Complications, Ethical Dilemmas, Marketing and Social Networks in Gynecology and other topics related to Regenerative Gynecology.

DIGITAL «MATURITY ASSESSMENT»: APPROACHES, METHODOLOGIES, TOOLS

Elisaveta Grebennikova — Mon, 02 Oct 2023 14:13:02 +0200

Relevance. The general trends and consequences of digital transformation have touched all levels of the education system, manifested in the creation of a digital educational ecosystem, significant changes in the theory and practice of teaching and education, the introduction of electronic and network didactic means and tools, the formation of a digital culture of an educational organization, etc. Digital transformation does not mean a set of IT programs or software, but, first of all, it is a transformation of the educational process, manifested in an innovative format of teaching, education and learning, forming a new thinking and culture of the subjects of educational relations, taking into account digital transformations in the economy and society. The solution of the actual task of assessing the 'digital maturity' of organizations of various forms of ownership, spheres of production activity, including the level of higher education, will contribute to the development of a model for assessing the 'digital maturity' for the general education system. Object of the study: digital maturity assessment. Subject: approaches, methodologies, tools for digital maturity assessment. Objective: to identify and describe approaches, techniques, tools for assessing digital maturity. Objectives: to analyze the essence and meaning understanding of the category 'digital maturity'; assessment of 'digital maturity', to analyze the existing foreign and domestic methods and tools for assessing the level of 'digital maturity' of organizational systems. Methods: comparative analysis of the concept of "digital maturity"; bibliographic search; methods of systematization and generalization of data. Conclusions: there is no unity of scientific attribution of the concepts of "digital maturity"; assessment of "digital maturity"; the concept of "digital maturity" and its assessment systems in the Russian Federation are studied mainly only in the framework of higher education. In the case of general education, these problems are insufficiently represented in scientific research, as well as the number of empirical descriptions of practices of digital maturity assessment in general education schools is insignificant. In this regard, there is a need to analyze the approaches, methods and tools for comprehensive assessment of the digital maturity of organizational systems. The results of such work will serve as a source for designing profiles of digital maturity levels in the general education system. Recommendations: the assessment of the level of "digital maturity" should become a reference point not only and not so much for the transformation of the processes of functioning of the education system in the Russian Federation, but for the systemic renewal of the entire education sphere.

CURRENT STATE OF FACILITIES AND EQUIPMENT WITHIN VOCATIONAL EDUCATION AND TECHNICAL SYSTEM GIVEN INTENSIFYING IMPORT SUBSTITUTION PROCESSES IN RUSSIA (CLUSTER ANALYSIS)

Elisaveta Grebennikova — Mon, 02 Oct 2023 10:41:02 +0200

Sanctions and import substitution processes in Russian enterprises have changed not only the catalogue of equipment used but, in many cases, even technological processes. This is a serious challenge for the vocational education and training system (VET), that has to adapt to new economic environment. The purpose of the preprint is to find out to what extant Russian VET organizations are prepared to solve the problem of updating technologies and replacing previously imported equipment based on the data obtained during an empirical study. The study is based on the methodology of acquisition of empirical data using an electronic form of a questionnaire that included 22 closed questions. Primary results obtained were processed applying cluster analysis, generalization, grouping and ranking approaches. As a result: a low degree of readiness of Russian VET organizations to take part in solving problems of import substitution and to participate in achieving technological sovereignty goals set by Government was revealed. The contribution of employers to the process of modernizing facilities and equipment in VET organizations turned out to be much less than it was expected. Different management strategies used by an educational organization has a little effect on the quality of its infrastructure. Availability of financial sources in the regions of Russian Federation and capability of organizations to obtain them play the leading role. The nature and level of influence of different factors on the effectiveness of the processes of modernizing infrastructure and import substitution in VET organizations are defined. Differences in management strategies used by VET organizations to solve the problems of facilities and equipment (diversification of funding sources, cooperation with employers, import substitution planning, personnel training) are specified. A set of factors and management strategies to improve the efficiency of facilities and equipment modernization and import substitution processes have been defined. The pending problem areas of infrastructure management in VET organizations were identified.

Parametric design and optimization of hand shape air morphing structure and its test validation

yuyang song — Sat, 30 Sep 2023 17:39:03 +0200

Soft inflatable actuators show several advantages in flexible and versatile behaviors. Comparing to traditional silicon based soft actuators, fabric-based counterpart shows outstanding benefit such as lightweight and stowable. However, there are lots of challenges on design fabric-based structure, due to the joining/bonding constrain, incompressible membrane structure behavior of the fabric material, and non-existing design and simulation platform. This paper presents a pipeline from design, simulation, and fabrication of a hand shape air morphing structure for optimized performance based on the parametric analysis to check the effect of inflation pressure, geometry of bonding line, stiffness of skin fabric and rigid bar element integration to the inflatable structure. A demo of the optimized sample was fabricated and compared with the optimized design. Such lab scale study shines a light for design and analysis of large-scale structure membrane structure with morphing functionality.

CONDITIONS FOR THE FORMATION OF STABLE FORMS PUBLIC-PRIVATE PARTNERSHIP IN THE SYSTEM OF SECONDARY VOCATIONAL EDUCATION

Elisaveta Grebennikova — Fri, 29 Sep 2023 12:51:03 +0200

The uneven socio-economic development of the subjects of the Russian Federation has a significant impact on the modernization of secondary vocational education and vocational training. There is a significant reduction in the number of graduates in the programs of training skilled workers in vocational education and training and the flow of this contingent into the vocational training sector. The number of SPO graduates who are employed in the received specialties and professions rarely reaches fifty percent. Labor migration of vocational graduates to more developed regions is steadily increasing. The amount of funding for vocational education programs depends on regional budgets, which leads to a significant territorial differentiation of investments in the human capital of students, as well as the material and technical base of educational organizations and their personnel. Fifty percent of the output of skilled worker training programs is concentrated within the 10 most sought-after professions. A similar situation develops in the training of mid-level specialists, where half of the graduates concentrate within 16 specialties. These and many other facts indicate a significant discrepancy between the results of personnel training in regional vocational education systems to the demands of labor markets, a decrease in the quality of education in vocational education, and the need to take targeted measures to improve the effectiveness of this level of vocational education as a source of staffing for the economies of the constituent entities of the Russian Federation. The purpose of the preprint is to present the results of the analysis of the conditions for the formation of sustainable forms of public-private partnership in the system of secondary vocational education. The results of the study can be applied in the formation of secondary vocational education and training programs based on digital technologies; the creation of systems of personnel support for vocational education and training, depending on the socio-economic development of the subjects of the Russian Federation.

Modern approaches to studying economic sanctions

Elisaveta Grebennikova — Fri, 29 Sep 2023 11:10:02 +0200

The Russian economy has been operating under sanctions pressure in recent years. And there are risks of further strengthening of sanctions pressure both from the restriction of financial relations with the outside world and from the restriction of trade. The paper presents an overview of modern research devoted to the study of various types of economic sanctions. Despite the fact that the introduction of economic sanctions is most often motivated by political goals, the effectiveness of this tool in achieving these goals
not always high. However, the economic consequences of sanctions are almost always they turn out to be significant.

Robust Inference on Income Inequality: t-Statistic Based Approaches

Elisaveta Grebennikova — Thu, 28 Sep 2023 15:16:05 +0200

Empirical analyses on income and wealth inequality and those in other fields in economics and finance often face the difficulty that the data is heterogeneous, heavy-tailed or correlated in some unknown fashion. The paper focuses on applications of the recently developed t-statistic based robust inference approaches in the analysis of inequality measures and their comparisons under the above problems. Following the approaches, in particular, a robust large sample test on equality of two parameters of interest (e.g., a test of equality of inequality measures in two regions or countries considered) is conducted as follows: The data in the two samples dealt with is partitioned into fixed numbers

Cointegration with time-varying parameters: literature review

Elisaveta Grebennikova — Thu, 28 Sep 2023 15:07:03 +0200

This paper reviews the literature devoted to the analysis of cointegrated time series in the economy, where the parameters of cointegration vary over time. The main studies that develop methods for modeling the movement of parameters, different approaches to evaluating the model, as well as tests for cointegration are considered. In addition, the areas of application of cointegration models with time-varying parameters in macroeconomic studies are highlighted.

HUMAN CAPITAL CONCEPT AND MECHANISMS OF ITS INFLUENCE ON ECONOMIC GROWTH

Elisaveta Grebennikova — Thu, 28 Sep 2023 14:48:03 +0200

Economic science considers human capital as a fundamental factor that stimulates the accumulation of productive capital and, accordingly, has a positive effect on economic growth. Improving labor force quality can lead to an increase in the well-being of an individual due to an increase in his labor cost. An increase in public welfare will affect the economic growth of the state as a whole. The above conditions the relevance and timeliness of this work, aimed at illustration of human capital concept (subject of the study), as well as determination of human capital place in theoretical economic growth models and empirical mechanisms of its influence on growth. A review of theoretical works analyzing human capital concept and its relationship with economic growth rates aimed at achieving this goal. The study was conducted at the IPEI Center for the Study of Central Banking Problems as part of the RANEPA state task for 2022 using relevant academic literature and as the major source of information and methods such as descriptive, statistical, comparative analysis, as well as systematic approach. Analysis of human capital concept allows concluding that this indicator represents a set of innate and acquired through investment knowledge, skills and practical skills that determine labor productivity and future income of an employee. The mechanisms of human capital impact on economic growth include the relationship between growth and education level, the impact of human capital on technological progress, the relationship between health indicators and economic growth rates, the growth effect of public spending on education and health, and, finally, the effect of human capital in terms of poverty reduction. In the future, this review can serve as a starting point for an empirical study of investments in human capital in Russia within the framework of models with uncertainty and individual heterogeneous discounting.

Autoregression model for the GDP of the Russian Federation, supplemented by the indicator of business activity of trading partner countries

Elisaveta Grebennikova — Thu, 28 Sep 2023 14:29:03 +0200

The model proposed in this paper is a modification of the second-order autoregressive process with the addition of an external variable
that allows taking into account the cycles of trading partners to predict output. This model has shown a significant advantage in forecasting for the long-term horizon, which confirms the importance of taking into account the economic activity of partner countries when forecasting the GDP of the Russian Federation.

Modeling the impact of news shocks on the economy in dynamic stochastic general equilibrium models

Elisaveta Grebennikova — Thu, 28 Sep 2023 14:17:03 +0200

This paper systematizes the experience of empirical research on
news shocks, in particular on models of vector autoregressions, as well
as dynamic stochastic models of general equilibrium. The review examines the work
with various types of shocks, presents the main disadvantages of different classes of models
used to analyze the impact of news shocks on developed and developing
economies. The main prerequisites that need to be included in the DSGE are highlighted
models so that these models can demonstrate a co-directional change
the main macroeconomic indicators in response to the news shock. It has also
been demonstrated that VAR models and DSGE models use many similar ideas –
it is useful to include predictive indicators in each of these models. During the research
it was found that the proportion of explained variation in works with DSGE models is very
different from the proportion of explained variation in works with VAR models. A possible
reason may be that VAR models are characterized by the problem
of non-fundamentality.

Analysis of the relationship between inequality and environmental pollution

Elisaveta Grebennikova — Thu, 28 Sep 2023 13:55:03 +0200

The regions of the Russian Federation are characterized by a strong differentiation of both the level of income and the level of emissions of pollutants into the atmosphere. Meanwhile, income inequality can both contribute to an increase in pollution levels and hinder its growth. In this regard, there are risks of increasing the amount of emissions into the environment when conducting inconsistent tax or social policies. The paper presents an overview of modern research devoted to the study of the impact of inequality on environmental pollution. It turns out that high levels of income inequality can have a positive impact on environmental pollution in developed countries and rich regions and a negative impact in developing countries and poor regions.

An algorithm for quickly finding long-term equilibria in models of overlapping generations

Elisaveta Grebennikova — Thu, 28 Sep 2023 13:33:03 +0200

In this paper, we consider the problem of finding long-term equilibria in models of overlapping generations with a large number of periods. It is often possible to reduce
the solution of a model to finding the roots of a system of equations. Some OLG models, after
the introduction of additional variables, can be reduced to the form of a system of polynomials. Thus, one can represent the set of long-term equilibria as algebraic
diversity. This makes it possible to use computational methods from algebraic geometry in economic problems. In particular, the method using Grebner bases has become popular. However, this approach can be effectively applied only
when there are few variables. We propose an algorithm for finding solutions to the system and use it to investigate the presence of a plurality of solutions in realistically calibrated
models with long-lived agents.

ANALYSIS OF PROMISING DIRECTIONS FOR THE DEVELOPMENT OF THE EAEU INTEGRATION WITH CONSIDERING ITS EXISTING FOREIGN TRADE RELATIONS

Elisaveta Grebennikova — Thu, 28 Sep 2023 11:32:02 +0200

Over the past century, as one of the main trends in international trade, one should note the noticeable liberalization of trade throughout the world, this trend is still widely supported today in the activities of many economic associations, ranging from the activities of the WTO and the IMF to the activities of economic associations in within the framework of regional trade agreements, for example, the EAEU, the EU and others. Along with the trend towards globalization, there is a decrease in non-tariff barriers to trade in goods and services, and other obstacles to capital flows. The issue of countries taking part in integration processes is widely discussed and debatable, as the object of study is the economies of the EAEU countries, the EU and the economies of Russia's key trading partners. The purpose of the study is to assess the consequences (macroeconomic and sectoral) for the EAEU countries from the implementation by various countries of a number of provisions of agreements governing the functioning of potential integration associations that include the EAEU, and, based on the estimates obtained, to form a profile of foreign trade policy strategies for the EAEU countries, taking into account internal and external situations for choosing the optimal integration directions of the EAEU. The results of the study presented in this paper are as follows: Calculations based on data in the form of a global matrix of social accounts for 2019 showed that under any bilateral scenario of Russia's integration with the 16 listed on the EAEU site, Russia is unlikely to be able to achieve an increase of more than half a percent of GDP. At the same time, no significant industry risks are expected for it. As the country-by-country analysis of the games showed, with the simultaneous entry of several countries into the EAEU, there are no noticeable synergy effects and Russia's gains are approximately equal to the sum of the gains from agreements with each of the partners.

Approximate solution of the fractional differential equation via the natural decomposition method

Ahmed Hagag — Thu, 28 Sep 2023 06:47:06 +0200

In today’s world, analyzing nonlinear occurrences related to physical phenomena is a hot topic. The main goal of this research is to use the natural decomposition method (NDM) of fractional order to find an approximate solution to the fractional clannish random walker’s parabolic (CRWP) equation. The proposed method gives approximate solutions that are exceptionally near the exact solution without the complication that numerous other techniques imply. Banach’s fixed-point theory is used to investigate the anticipated issue’s convergence analysis and uniqueness theorem. To ensure that the suggested technique is trustworthy and precise, numerical simulations were conducted. The results are shown in the graphs and tables. When comparing the proposed scheme’s solution to the actual solutions, it becomes clear that the scheme is efficient, systematic, and very precise when dealing with nonlinear complex phenomena.

Comparative legal analysis of Green Finance market regulation in OECD countries and in Russia: present experience and harmonization challenges

Elisaveta Grebennikova — Wed, 27 Sep 2023 16:36:03 +0200

The paper analyzes the regulation of the green finance market in Russia and in the world, and also formulates proposals for the development of regulation in order to improve Russian mechanisms for sustainable (including green) development and harmonize the Russian approach to such regulation with international approaches. The relevance of the work lies in the need to develop regulation of the market for sustainable (including green) financing in Russia, taking into account the growth in the size of the global market, as well as the development of such regulation in foreign countries. The object of the research is the regulation of the market for sustainable (including green) financing in Russia and in the world. The purpose of the study is to formulate proposals for regulating the market for sustainable (including green) financing in Russia in order to improve Russian mechanisms for sustainable (including green) development and harmonize the Russian approach to such regulation with international approaches. Based on the study, the following results were obtained: an analysis was made of the approaches of foreign countries and international organizations in the field of regulation of green finance; an analysis of the regulation of green finance in Russia was carried out, inconsistencies between Russian practices of such regulation and international ones were identified. In addition, the risks that such a discrepancy creates were described; proposals for the development of market regulation in Russia were formed, taking into account the best international practices. The practical significance of the work lies in the possibility of using its results for the development of regulatory legal acts aimed at developing the regulation of the market for sustainable (including green) financing in Russia.

Assessment of the impact of major infrastructure projects on the development of integration processes in the CIS countries

Elisaveta Grebennikova — Wed, 27 Sep 2023 15:57:02 +0200

The relevance of the study is determined by the need to fill a gap in academic and practical research on the effects of infrastructure projects on the economic development of countries. Since the economic development of countries may depend on the indicators of the sectoral development of neighboring regions: there is a need to answer the question of the significance of different initial levels and the further pace of economic development of countries on the effectiveness of their cooperation. As one of the main factors of spatial economic development, it is proposed to consider infrastructure, the development analysis of which is proposed to be compared with the dynamics of macroeconomic indicators of countries, including international trade, the development of integration. This problem is of particular relevance for the CIS countries, where a large number of national, regional and international infrastructure projects are being implemented. Of particular interest in the study of the countries of the post-Soviet space are the so-called partially recognized republics. The situation around the Ukrainian crisis and the subsequent unprecedented sanctions against Russia adds relevance to the study of the problems of post-Soviet countries, their integration and the development of infrastructure projects. In the last ten years, there has been an increase in the activity of studying these problems, in connection with the development of the European neighborhood policy on the one hand and Eurasian integration on the other. The ambiguity of terminology in the field of infrastructure projects is noted. Among the researchers of the impact of infrastructure projects on economic development, one can single out, for example, O.Yu. Patrakeev, K.P. Glushchenko, I.V. Mitrofanov, as well as some authors studying infrastructure projects in China: S. Barizits, A. Radzyner, A. Gabuev, F. Jai, Y. Kaho, S. Chan, A. Garcia-Herrero; X. Jianwei and others.

FOOD DEVELOPMENT STRATEGIES OF RUSSIA AND THE USA: A COMPARATIVE ANALYSIS

Elisaveta Grebennikova — Wed, 27 Sep 2023 13:54:03 +0200

The relevance of the food superpower study is determined not only by the scientific interest of agrarian economics, sociology or history, but, primarily, by the tasks of agricultural policy, by the need in strategic and practical decisions of the subjects of public administration. The study aims at a comparative analysis of the food development strategies of Russia and the United States in the historical and contemporary perspectives. The subject is food-development and food-security strategies applied by Russia and the USA. Interdisciplinary and comparative methods are used to identify the key features of the food and agro-industrial development in two countries. Based on the results, the study presents not only environmental or technological factors in the formation of the agrarian strategies of the USA and the USSR, but also political and economic factors (American depression and Soviet collectivization; NeoNEP in the USSR and the New Deal in the USA). The paper concludes with a set of variables for the study of strategies for becoming a food superpower and for keeping this status: at the stage of becoming a food superpower – state policy to support agriculture, introduction of new technologies and methods of farming, development of consulting services, agricultural cooperation, wholesale markets and supply chains, social development of the village and information infrastructure, integration with world markets and expansion of food trade; at the stage of keeping and strengthening the status – the use of the newest technologies and agricultural practices, effective consulting services, expanding links with retail markets and international food trade, regional climate resilience. The novelty of the study is determined by the attempt to model a path for becoming a food superpower based on the comparative analysis of the US and Russia food strategies, and by testing of the hypothesis that there are two stages in the evolution of a food superpower. Based on the study of the real global leadership of Russia and the United States as wheat exporting countries and of the planned development of organic food production, the paper provides some recommendations on the possible ways for combining these two strategies and overcoming their limitations.

Trade policy priorities of the leading states in the context of post-COVID global economic recovery

Elisaveta Grebennikova — Wed, 27 Sep 2023 11:24:03 +0200

Due to the changes in the geo-economic situation at the beginning of 2022, the focus of this research is shifted from the general analysis of foreign trade strategies of foreign countries to the study of trade policies of key countries against Russia (including common approaches and sanctions), as well as the response of the Russian side. This approach determines the novelty and relevance of this study. The significance of the work is determined by the research in scientific and applied aspects of the problems of forming common priorities and tools in trade policy of the leading countries of the world, which depend on the global scientific and technological development. Trade policy is a purposeful activity of the state to promote and protect the interests of national business in global markets. The results of the study indicate attempts to create and consolidate new rules of the world economy based on the concept of energy transition and technological breakthrough, which has a negative impact on the established rules of the world economy and international trade.

Opportunities and Constraints for G20 Leadership in Data Governance

Elisaveta Grebennikova — Wed, 27 Sep 2023 09:53:02 +0200

The working paper studies the approaches of the digital economy leaders (the US, the EU and China) to data governance and approaches they promote in international institutions. Data can generate not only profits for tech giants, but also social value. However, the market forces by themselves will not create data-based public goods. Government actions are needed at the county level and inter-state and multilateral institutions cooperation at the international level. The study is highly relevant, since to date despite numerous initiatives to establish coordination mechanisms and data regulation, cooperation on data governance is highly fragmented and gridlocked due to contradictions and tough competition between key players. One of the key disagreements is related to the regulation of cross-border data flows. The working paper aims to explore contradictions between the regulatory practices of the key actors in digital economy, the US, EU and China in the first place, and approaches they promote in international institutions (the WTO, G20, G7, OECD). In particular, the author looks into the G20 agenda on data governance and the Initiative on free data flow with trust, its challenges, and risks of cooperation stagnation. The working paper presents possible scenarios of future cooperation on data governance, their risks and perspectives, including the establishment of the Digital Economy and Data Governance Board by the G20, G7 initiative on shaping global digital order, deepening of cooperation on data governance within the G7 and the OECD, and the UNCTAD proposal on building a multilevel distributed polycentric data-governance model with the UN central role. The author concludes with a proposal on BRICS cooperation aimed at shaping inclusive multilateral data governance.

A LOOK AT INFLATION IN THE RUSSIAN ECONOMY THROUGH THE PRISM OF THE PHILLIPS CURVE

Elisaveta Grebennikova — Tue, 26 Sep 2023 16:19:02 +0200

This paper is devoted to the estimation of the Phillips curve for small open economies with the inclusion of the expected change in the real exchange rate of the ruble. The nonlinear generalized method of moments (CUE GMM) is used as an estimation method. According to the estimates obtained, the dynamics of inflation in Russia depends on external factors, in particular on expectations about changes in the terms of trade. At the same time, the role of expectations in the formation of inflation has undergone several significant changes. The first change is associated with the transition to the inflation targeting regime, the second with the outbreak of the pandemic. In addition, the rigidity of prices was also subject to changes under the influence of these factors.

THE IMPACT OF PROGRESSIVE TAXATION REFORMS ON DEVELOPED AND DEVELOPING ECONOMIES: WHAT THE LITERATURE SAYS

Elisaveta Grebennikova — Tue, 26 Sep 2023 15:51:03 +0200

The progressive tax system is a tax structure in which the tax rate increases as the taxpayer's income level increases. This means that people with higher incomes pay a larger percentage of their income in taxes than people with lower incomes. The relevance of this work is determined by the fact that currently the issues of reducing inequality and increasing economic growth remain on the agenda of both developed and developing countries, and for the latter the problem of reducing poverty remains acute. In turn, tax system reforms have an impact on the macroeconomic indicators listed above and, thus, can serve as a tool for regulating inequality and poverty, as well as a way to accelerate economic growth. The main purpose of the study is to systematize the results of empirical studies examining the impact of progressive taxation reforms on inequality, poverty and economic growth in countries with different levels of development (subject of the study). A review of academic literature (source of information) devoted to the analysis of the impact of progressive tax reforms on inequality, poverty and economic growth in developed and developing economies contributes to the achievement of the stated goal (research objectives). The study was conducted using such methods as descriptive, statistical and graphical analysis, data analysis, a systematic approach, and comparative analysis. According to the results of the study, it can be concluded that 1) progressive taxation reforms can play a significant role in reducing income inequality in developed countries by redistributing income and providing financing for social programs and services that benefit low-income households; 2) the impact of such reforms on economic growth in developed countries depends on the specific structure of the tax system. the system and the broader economic context in which reforms are being implemented; 3) the described reforms can potentially become an effective tool for poverty reduction in developing countries, but their success will depend on a number of factors, including the specific conditions of each country and the quality of governance and institutions; 4) the impact of progressive tax reforms on economic growth in developing countries is a complex issue that depends on various factors, and the actual impact it can vary greatly depending on the specific circumstances of the country under consideration (scientific novelty of the work). In this regard, a promising direction for future research on this issue is a review of the main approaches to modeling the impact of progressive taxation reforms on macro indicators in developed and developing countries. The results of the review can also be used to develop tax policy measures in the Russian Federation aimed at reducing inequality and increasing economic growth in the country.

Return factors of Ether cryptocurrency: on chain metrics and DeFi

Elisaveta Grebennikova — Tue, 26 Sep 2023 14:57:04 +0200

In this study, we analyse whether such inner features of Ethereum blockchain as creation of smart contracts and decentralized applications influence in any way the price dynamics of Ethereum’s native cryptocurrency Ether or the latter can be mainly explained by the cryptocurrency market movements. Our results show that various on-chain metrics and total value locked in Ethereum’s DeFi protocols are almost insignificantly correlated with Ether returns on daily and weekly data. The corresponding regression models are also not able to explain a sufficient part of the variation of Ether returns relative to USD and BTC.

Beyond Bitcoin: A Taxonomy of Cryptocurrencies in a Historical Perspective

Elisaveta Grebennikova — Tue, 26 Sep 2023 13:21:04 +0200

The field of cryptocurrencies has been in existence and dynamically developing for over 14 years. Each year sees the advent of new cryptocurrencies, with their total count now exceeding 8,500, and it is evident that these differ from one another in some respects. However, there currently exists no exhaustive categorization of cryptocurrencies that could comprehensively describe the landscape of the cryptocurrency market. This situation underpins the relevance of the present study. The object of this study is cryptocurrencies. The aim of the research is to create a taxonomy of cryptocurrencies based on their primary characteristics and functions. The main method of research is a retrospective analysis of the development of the cryptocurrency sector from the creation of Bitcoin to the present day. Over the course of the industry's evolution, new projects emerged, substantially different in their properties from anything that had come before, thus forming entirely new categories and niches in the cryptocurrency space. Furthermore, the advent of certain types of cryptocurrencies could lead to changes in the existing classification. The outcome of this study is a hierarchical categorization (taxonomy) of interchangeable cryptocurrencies/tokens. The proposed taxonomy is supplemented by an in-depth examination of cryptocurrencies belonging to each category, as well as a consideration of the largest cryptocurrencies in terms of capitalization through its prism. The scientific novelty of this research lies in the absence of similar studies that look at the issue of categorizing cryptocurrencies through a historical lens.

DIVERSIFICATION OF AGRICULTURAL PRODUCTION AS A SOURCE OF SUSTAINABILITY OF INCOMES OF AGRICULTURAL PRODUCERS AND AND A PATHWAY TO DECREASE THE ECOLOGICAL EXTRENALITIES

Elisaveta Grebennikova — Tue, 26 Sep 2023 12:23:04 +0200

The relevance of the study is determined by the need to analyze the consequences of monocultures in crop production in the regions of Russia, not only from an economic point of view, but also from an environmental one. The objective of the study is to develop ways for the sustainable development of agriculture in Russia, taking into account the possibilities for the development of diversification and the possibility of reducing greenhouse gas (GHG) emissions. The subject of the presented research is the production and environmental indicators of crop production in the regions of Russia. In the course of the work, traditional scientific methods were used - descriptive, analytical, statistical and methods of economic and mathematical modeling. The sources of information were Russian and foreign scientific publications, official publications of regulatory and legal documents and statistical data of Russian state authorities, as well as foreign databases on agricultural statistics. The results of the study conclude that in the period 2011-2019, the increase in crop production took place mainly in the Central Black Earth and South-Western regions of the country, where the plowing of abandoned lands was accompanied by an increase in crop yields (intensification), which led to a relatively low carbon track per unit of output. On the contrary, in the regions of the Far East, where the plowing of the fallow has led to an increase in soybean crops (usually low-yielding), this has affected a higher carbon footprint, which cannot be considered a sustainable characteristic for further development. Thus, the scientific novelty of the study lies in the development of scientific and analytical tools for the correct identification of regional and global environmental risks in assessing the efficiency of crop production in the regions of Russia. Thus, in our study, regional risks were assessed through the concentration of crops in the region or through the diversification index (variety of cultivated crops). Global risks were assessed through the indicator of greenhouse gas emissions, which also allowed us to estimate the so-called cumulative "carbon footprint" of each region in terms of grain unit of crop production. As a result of the study, policy recommendations were developed to improve statistical reporting on the agricultural sector. It is also recommended to promote knowledge about new and old practices for introducing diversification, incl. and the classic method of growing legumes in crops, which is not being successfully implemented by all regions so far.

Digital economy non-market components accounting methodology

Elisaveta Grebennikova — Tue, 26 Sep 2023 10:48:02 +0200

An inclusion of non-market goods and services which are core to the digital economy in the system of economic circulation affects the basic socio-economic indicators both in Russian and in international practice. In this connection, the goal of this study is to develop a methodological basis for accounting and measuring non-market components in the emerging digital economy of the Russian Federation. As methods and methodology of the study, we use the provisions of the 2008 SNA methodological base relating to the accounting of new objects in the system of economic turnover; methods of forming input-output tables in the SNA application system; methods of transforming the indicators of the formation and use of resources into a system of indicators of symmetric input-output tables; methods of matrix calculations in building indicators of intersectoral relations, taking into account the digitalization processes of the Russian economy; methods of accounting the influence of price and hedonistic The main are: the development of a methodological framework for accounting for nonmarket components in the formation of a system of indicators of the digital economy; the development of methodological approaches to the valuation of non-market components in measuring the economic effects of digitalization; testing the proposed methodology for accounting and measuring non-market components in the digital economy based on Russian data, and developing recommendations for using the results in the formation and implementation of economic and industrial.

DETERMINATION OF THE NATURE OF THE CYCLICAL FISCAL POLICY OF DEVELOPED AND DEVELOPING COUNTRIES

Elisaveta Grebennikova — Mon, 25 Sep 2023 15:52:02 +0200

The relevance of the study is due to the fact that, caused by the coronavirus pandemic of 2020, it put on the agenda issues about choosing the best methods to support businesses and citizens. However, the choice, evaluation, and practical choice of steps faces with the still existing lack of elaboration of the methodological aspects of performance evaluation. Both instruments (tax expenditures and direct expenditures) have their own advantages and implementation, their application should be directly linked to the goal. The subject The subject of the study is the list and mechanisms for the formation of tax expenditures used as part of support measures. The aim of the study is to determine how to use the methodological approaches accumulated in the scientific literature and international experience to the definition and assessment of tax expenses, as well as their accounting and management. When forming the work, such methods as reasoned-critical analysis, hypothetical-deductive method, case methods, method of analysis of generalizations and extrapolation (interpolation) of results were used. The study used data from the Federal Treasury, Rosstat and the Ministry of Finance of Russia and GTED Database. The scientific novelty of the study consists in the use of new data to analyze the structure of tax expenditures and compare the methodologies of different countries. The result of the work was a report containing: 1. Generalization of methodological approaches to the definition and evaluation of tax expenditures in scientific research 2. Analysis of international experience in accounting and management of tax expenditures 3. Analysis of the Russian practice of granting tax expenditures 4. Evaluation of the effect of the introduction of the fiscal rule on the nature of the cyclicality of fiscal policy in developed and developing countries 5. Description of opportunities for optimizing tax expenditures in the Russian Federation. The results obtained allowed us to conclude that the Russian tax system is replete with too many deviations from the standard rules, which produce a significant amount of tax expenditures by world standards. In addition, the stated goals of preferences do not fully correspond to the distribution of tax expenditures by type of tax. Part of the tax expenditure generated under indirect taxes is implicitly intended as a tool to stimulate business and investment. This creates an opaque system for distributing preferences and comparing their volume (imputed subsidy) with the result. In turn, this contributes to the strengthening of the effect of fiscal illusion. In the future, the authors plan to continue the study of the effectiveness of tax expenditures in Russia and the world.

Analysis of trends in legal regulation of employment on online platforms in the world and in Russia

Elisaveta Grebennikova — Mon, 25 Sep 2023 15:25:03 +0200

The subject of the study is the analysis of legal relations arising in connection with employment on online platforms, including the provision of minimum labor guarantees by the platforms, regulation of self-employment, taxation, social insurance, cab platforms and courier services. The relevance of the study stems from the fact that a number of countries, including Russia, are trying to develop approaches to regulate the application of labor law, taxation and social insurance to persons providing services or work through platforms. In addition, there are various aspects of the regulation of employment on platforms in certain sectors of platform work, in particular in the provision of cab services and courier delivery. The novelty of the study lies in the fact that the work solves the problem of creating in Russia an effective system of regulating the status of persons working through online platforms, employment on online platforms, taking into account the standards of international organizations. The purpose of the study is to formulate proposals for the extension of minimum labor guarantees (the right to work safety, to guaranteed wages not lower than the minimum wage, the right to protection against unemployment, the right to rest, etc.) to persons providing services or work through platforms, as well as to determine the criteria for the existence of labor relations with such persons, the possibility of recording the labor (insurance period) of self-employed working through platforms, social insurance and taxation, regulation of cab and courier platforms activities etc. The methodology of the study is based on the application of methods of logical, systematic and comparative analysis using Russian and foreign normative legal acts, analytical materials of competent authors and international organizations. As a result of the study proposals for the development of the regulation of employment on online platforms, as well as the status of persons employed on the platforms, based on the analysis of OECD standards and the legislation of member countries and partners of the Organization are formulated. In order to achieve the goal the following tasks are planned: analysis of the standards of the OECD and other international organizations on the regulation of the status of persons working through platforms and platform employment on the application of labor law, tax law, social insurance law, on the regulation of cab and courier services, on the formation of statistics; analysis of the experience of the OECD member states in regulating the status of persons working through platforms and platform employment; analysis of legal problems in Russia related to the regulation of the status of platform workers and platform employment; the formation of proposals for the development of legal regulation of the status of persons working through platforms and platform employment in Russia, including in terms of the adoption of response measures that affect the development of online employment. The results of the study were the development of proposals for Russia on the development of guarantees for persons employed on online platforms in terms of providing some rights similar to labor, the development of taxation and social insurance, statistical records of platform employment, providing guarantees in certain industries (cab services and courier services). The perspective of the study lies in the need to improve the Russian legislation in terms of protecting the rights of persons employed on platforms, which enter into a relationship with the platform, similar to labor.

DIRECTIONS OF AGRICULTURAL DEVELOPMENT IN THE REGIONS OF THE RUSSIAN RURAL PERIPHERY

Elisaveta Grebennikova — Mon, 25 Sep 2023 14:52:10 +0200

The relevance of the study is determined by the fact that in recent decades, peripheralization of rural spaces in Russia has intensified in the form of the expansion of abandoned agricultural lands, disappearance of rural settlements, and a general long-term social-demographic depression. Concerning the spatial and food security of Russia, the re-development of peripheral rural territories is the most important condition for the viability and sustainable development of the country. The study aims at presenting a typology of models of rural development and rural differentiation in the peripheral territories of Russia as based on regional resources and the potential of local territories – in order to integrate them into the all-Russian programs of rural development. The subject is specific Russian cases of the development of rural peripheral territories and general trends in the revival of the depressed rural periphery. The methods combine the elements of the quantitative (statistical data, secondary analysis) and qualitative (expert semi-formalized interviews) approaches within the case study. Based on the results of the study, the paper describes the latest trends in the peripheralization of even the old-developed Russian regions, i.e., measures for the centralization of spatial development often exacerbate the depth of peripherization. The paper concludes with the main indicators of the rural periphery viability (ability to cope with systemic shocks and uncertainty, ability to radically change the trajectory of one’s development) and the features of the sustainable peripheral rural system. The novelty of the study is determined by an attempt to develop a typology of rural periphery and by a systematic analysis of its problems within both the agrarian re-development strategies and projects of ecological-recreational and cultural-historical types. The paper provides some recommendations on the development of rural periphery: more diverse economic activities of rural residents; more market-oriented institutions to ensure a transition from informal economic interactions to the formalized ones; stronger social capital in order to more easily mobilize internal and external resources.

Exchange rate shocks and foreign trade of Russian manufacturers

Elisaveta Grebennikova — Mon, 25 Sep 2023 13:25:17 +0200

The goal of this paper is to empirically assess the impact of exchange rate shocks on prices and quantities of Russian exports and imports. The relevance of the work is dictated by the sanctions imposed on Russia in 2022, which can complicate international payments in the dominant currencies in international trade, and by subsequent economic policy measures aimed at reducing the role of the dollar and the euro in Russian foreign trade. Modern studies consider the currency of the contract as one of the most important factors influencing the magnitude of the exchange rate pass-through effect on prices and quantities of exports and imports. The main assumption of such models – short-term price rigidity in terms of contract currency – matches the behavior of real data. These models also predict the dependence of the pass-through effect on the firm's share of the product-country market. In this paper, based on econometric analysis of detailed data from customs statistics of the Russian Federation, it is shown that the key to the dynamics of exports and imports is not bilateral exporter-importer rates, but exporter and importer rates to the dominant currencies in world trade (US dollar and euro), and prices are rigid in the contract currency. Because of the asymmetry in the response between importer currency shocks and exporter currency shocks to the contract currency, there is a statistically and economically significant effect of a uniform appreciation of the dominant currency. This means that Russia's foreign trade prices and quantities respond to the dynamics of the contract currency even if neither the exporter nor the importer is a country issuing the contract currency. This response persists in the long run, and therefore cannot be explained solely by short-term price rigidity. The pass-through effect depends on the value of exports and imports, which is consistent with the predictions of the theory. The main conclusion of the paper is that diversification of the currency structure of foreign trade contract payments will contribute to the sustainability of Russian foreign trade, but the question of the costs of such a transition remains beyond the scope of this study.

ANALYSIS OF THE READINESS OF BUSINESS, THE FINANCIAL SECTOR AND THE STATE TO INCREASE INVESTMENT ACTIVITY IN THE POST-PANDEMIC PERIOD IN RUSSIA: KEY RISKS AND INCENTIVE MECHANISMS

Elisaveta Grebennikova — Mon, 25 Sep 2023 11:47:04 +0200

The relevance of the study is determined by the urgent need to assess the potential conditions for the consolidation of public and private resources and the capabilities of the financial sector in the implementation of large-scale investment programs. The purpose of the study is to assess the ability and readiness of key economic agents and the financial system to increase investment activity in Russia. The subject of the study is the analysis of the main trends and features of the formation of investment resources by sources of financing and forms of ownership, characteristics of financial and material potential of investment and construction activities. The analysis of investment activity trends was carried out on the basis of methods of comparative analysis of official statistical data, review of strategic planning documents and regulatory and legislative framework. As a result of the study, general and specific features of investment activity in the period 2015-2021 were identified and systematized. Overcoming the consequences of crisis phenomena in the investment sphere is considered in the paradigm of changing the role and participation of the state, business, population and financial markets in resource mobilization and financing of investment projects. The analysis of trends in the formation of the material structure of investment resources allowed us to draw conclusions about the impact of imports of investment goods and determine the potential of domestic production in solving import substitution problems as a factor of innovation and technological modernization of the economy. The evaluation of the system of anti-crisis measures to support and finance investment projects allowed us to determine the potential for mobilizing budgetary and extra-budgetary sources and the distribution of risks between the state, private business and the population. The scientific novelty of the study consists in summarizing the current data on the state of the investment sphere, the practice of regulatory and organizational and managerial impact and assessing the financial sector's capabilities in consolidating resources. The recommendations based on the results of the study are related to the need to further improve the methods of state stimulation of investment activity and the development of tools for consolidating the resources of the public and private sectors, increasing the coherence of investment programs for industrial, technological, infrastructural and social development, reducing the risks of spatial and territorial differentiation and resource provision of investment programs.