Polystyrene Concrete Research Articles

Achieving sustainable performance: synergistic effects of nano-silica and recycled expanded polystyrene in lightweight structural concrete

Lightweight concrete, particularly polystyrene concrete, has been extensively utilized in civil engineering for decades. The incorporation of waste expanded polystyrene (EPS) as a filler material in the production of lightweight concrete presents significant advantages from a circular economy perspective. Prior research indicates that increasing the proportion of lightweight aggregates, such as EPS, typically results in reductions in strength and bulk density. The utilization of substantial amounts of EPS waste in the formulation of structural polystyrene concrete is crucial for advancing sustainable construction practices. This study investigates the effects of varying nano-silica content on the bulk density, compressive strength, flexural strength, splitting tensile strength, and water penetration depth of structural polystyrene concrete. Concrete specimens were prepared by substituting 25%, 50%, 75%, and 100% of sand with EPS waste, while evaluating nano-silica contents of 0.75%, 1%, and 1.25%. The findings reveal that increasing the volume fraction of EPS corresponds to a decrease in the concrete’s bulk density. This research provides critical insights into optimizing structural lightweight concrete, thereby promoting advancements in sustainable construction applications.

The Effect of Fly Ash Additive on the Thermal Conductivity of Polystyrene Concrete

The use of fly ash in compositions as a substitute for a part of cement is economically favorable and ecologically feasible in connection with large accumulations of waste at the enterprises of the energy sector. In addition, the technology of cement production provides high-temperature treatment of mineral substances in kilns with significant emissions of carbon dioxide. One of the most effective directions of the utilization of fly ash is their use in concrete composites. The use of this material will provide the required temperature and humidity conditions in residential premises, solve the problem of “cold bridges” in structures, minimize heat losses of the structure, and increase the energy efficiency of buildings in general. At the same time, polystyrene concrete, due to its structural structure and the presence of thermally conductive concrete, has limited opportunities for thermal and physical–mechanical properties. To improve the operational properties of polystyrene concrete, it is proposed to use composite binders, including fly ash from the thermal power station of Astana. The main aim of this study is to develop compositions of polystyrene concrete with reduced thermal conductivity and improved physical and mechanical properties. The objectives of this study include the determination of characteristics of fly ash from Astana, formulation of polystyrene concrete mixtures with different proportions of fly ash, and evaluation of their thermal conductivity properties. These tasks are in line with the objectives of the ISO 50001 standard to improve energy efficiency and reduce environmental impact. The results showed that the addition of fly ash from Astana to polystyrene concrete leads to a marked reduction in thermal conductivity, contributing to improved energy efficiency of the building envelope. Optimal results were achieved by using 15% of Astana fly ash as an additive in polystyrene concrete, which led to a significant reduction in thermal conductivity of 51.47%. This reduction is in line with improving the energy efficiency of building materials, especially in cold climates.

Computational Research of the Efficiency of Using a Three-Layer Panel Made of Highly Porous Polystyrene Concrete.

This paper presents linking computational research of the multilayer structure of the cladding of a three-layer panel made of highly porous polystyrene concrete developed using a new technology in comparison with traditional ones. The calculation of the thermal efficiency of the exterior fence was carried out in three stages, where the thermal regime was calculated from the values of temperature fields in the ELCUT 6.6 system, and the humidity and air modes were determined by the analytical method in the Maple system. The territory of central Kazakhstan (Karaganda) was selected as the research region, where the research showed that equating the thickness by the values of the actual and required heat transfer resistances of traditional multilayer structures to the developed one, the thickness of traditional structures increases from 3.09% to 27.83%. Moisture accumulation relative to the developed one occurs in all the studied structures. Thus, if in some cases of traditional structures moisture is collected by 2.61% and 9.48% less, in others moisture is collected by 27.94% and 119% more. However, the value of evaporated moisture during the drying period showed that all the moisture will evaporate during the specified period. Thus, all the structures meet the conditions for the inadmissibility of moisture for the annual period and the period of moisture accumulation. Moreover, the values of the actual and required permeabilities to air satisfy the condition, which affected the values of the temperature fields taking into account air filtration; the developed structure showed a positive effect for this value, and in traditional structures, the value of τint decreased to 1.35 °C depending on the option. The analytical results of the thermal inertia values of the developed and traditional multilayer structures showed that the developed structure exceeds traditional ones by up to 30.04% depending on the option, which is positive in the cold period. It was also found that the market prices of all traditional structures exceed the developed one by 1.2-2.5 times, depending on the design, which also emphasizes the positive aspects of the new design. Thus, the findings of this research will positively complement the catalog of products of external multilayer cladding structures made of effective materials and can be used by research communities and design organizations in the design of residential buildings.

Effect of High-Tenacity Polypropylene Fibers on the Carbonation Resistance of Expanded Polystyrene Concrete

Expanded polystyrene concrete (EPSC) is increasingly utilized in buildings as a green building material. To investigate the effect of high-tenacity polypropylene (HTPP) fibers on the carbonation resistance (CR) of EPSC, five groups of EPSC specimens with HTPP fiber volume fractions of 0%, 0.6%, 0.9%, 1.2%, and 1.5% were prepared. Rapid carbonation tests were conducted to measure the carbonation depth (CD) and uniaxial compression strength (UCS) of the specimens at different carbonation ages (3, 7, 14, and 28 days). The CD and UCS of the specimens were calculated and analyzed. The results indicated that the HTPP fibers dramatically improved the CR of EPSC, with a decrease in the CD of up to 29.5% at 28 days. A model for predicting the CD of EPSC was developed. The model for the strength after carbonation also showed good agreement with the experimental results. Scanning electron microscopy (SEM) was used to examine the microstructure of the HTPP-reinforced EPSC, while the mechanism of HTPP fibers to enhance the CR of EPSC was elucidated. The findings of this study provide valuable insights for the application of EPSC as a structural material.

A study on the effect of microspheres on the freeze–thaw resistance of EPS concrete

Abstract This study investigated the influence of microbead dosages (0, 5, 10, 15, and 20%) on the frost resistance of expanded polystyrene (EPS) concrete. Five groups of EPS concrete specimens were prepared and subjected to rapid freeze–thaw tests. The freeze–thaw deterioration of EPS concrete was assessed using macroscopic indicators, including mass loss, strength loss, and dynamic elastic modulus loss. The underlying deterioration mechanism was revealed through the analysis of the EPS particle–matrix interface. A concrete damage plasticity model of EPS concrete based on damage mechanics theory was established. The results indicate that the addition of microbeads increased the strength of EPS concrete by 38–53%, reduced the strength attenuation after freeze–thaw damage by 8.1%, and improved the frost resistance level by 10–60 grades. The optimal dosage of microbeads is 15% of the cementitious material. The interfacial transition zone gaps in EPS concrete with added microbeads after freeze–thaw cycles are smaller, contributing to a more complete hydration reaction. The freeze–thaw damage model established in this study accurately reflects the freeze–thaw damage law of EPS concrete and provides a reference for studying the mechanical properties of EPS concrete under freeze–thaw cycles. The research findings of this study can enhance the strength and service life of EPS concrete, expanding its application scope as a structural material. The study provides valuable insights for future research and engineering applications related to the frost resistance of EPS concrete.

Residue fluidized catalytic cracking in lightweight polystyrene concrete: A sustainable construction solution

This study explores the potential of Polystyrene concrete, a globally recognized lightweight concrete, in the context of Vietnam's construction industry. The research incorporates non-hazardous industrial waste, specifically Residue Fluidized Catalytic Cracking (RFCC), as a novel additive in the production of lightweight concrete. The systematic approach involves evaluating different cement types and gradually replacing cement with RFCC to identify an optimal formula for lightweight Polystyrene concrete. The study aligns with global sustainability goals and addresses local gaps by contributing practical insights and solutions to challenges in traditional brick production. The experimental setup utilizes Expanded Polystyrene (EPS) granules, standard cement types (PCB50, PCB40, and PCB30), and super foaming additives. Results indicate the feasibility of replacing up to 10% of cement with RFCC, offering a promising avenue for effective industrial waste management. This research aligns with the Sustainable Development Goals (SDGs) and contributes to a more environmentally conscious scientific community.

МОДЕЛЮВАННЯ ПОКАЗНИКІВ ЕФЕКТИВНОСТІ ЗВЕДЕННЯ ЖИТЛОВОГО КОМПЛЕКСУ «АВІНЬЙОН»

This article is dedicated to modeling performance indicators of the comprehensive process of constructing a multi-story building while varying influencing factors, taking into account existing constraints, and utilizing modern software complexes. During the modeling process, the following solution for wall construction was employed as a component of the comprehensive building process: the installation of lightweight steel thin-walled structures (LSTW) with non-removable formwork cladding and filling with polystyrene concrete. Previous research has established that this construction and technological solution is the most effective among the compared alternatives. Building upon prior investigations, experimental-statistical modeling of the «construction duration», «construction cost», «average intensity of funding», and «maximum intensity of funding» indicators was performed, varying factors such as the «overlap coefficient of processes» and «number of working hours per week». Modeling was conducted using the COMPEX software complex. The values of efficiency indicators were obtained according to selected experimental plans by constructing economic (budgetary calculations) and organizational-technological (work performance schedules) models using the AVK 5 and Microsoft Project software complexes, respectively. During the experimental-statistical modeling, extremes of efficiency indicators and corresponding values of factor combinations influencing them were determined. The nature and degree of the factors' impact on the investigated efficiency indicators were identified. The «construction cost» indicator was subjected to an existing constraint in the form of using credit funds. The calculation of the impact of imposing this existing constraint was performed in the Microsoft Excel software complex. While varying the factorial space, diagrams of changes in the budgetary cost of building construction and the amount of funds needed to secure the loan were constructed. Combining these diagrams resulted in values for the «construction cost with consideration of credit funds». It was determined that the use of credit funds at a level of 90% significantly increases the cost of building construction. On average, this increase amounted to 183,8 million UAH. Graphical dependencies were constructed using the CorelDraw X6 software complex.

Investigation of the mechanical properties of lightweight concrete using expanded polystyrene reinforced with glass fibers

The use of lightweight concrete has gained popularity in the industrial construction sector owing to its ability to reduce dead weight and enable smaller cross-sections of beams. Adding expanded polystyrene to replace a portion of fine aggregate is a widely accepted solution to decrease the weight of concrete. However, lightweight expanded polystyrene concrete (EPSC) has poor mechanical properties and brittleness, limiting its application to non-bearing structures and thermal isolation. Glass fiber reinforcement is a promising solution to improve the mechanical properties of lightweight expanded polystyrene concrete. This study investigates the effect of glass fiber content on the mechanical properties of lightweight expanded polystyrene concrete. To investigate the impact of glass fiber on the mechanical properties of concrete, various volume percentages of glass fiber were incorporated into the mixture. The compressive and tensile strengths of the concrete were measured and compared for each percentage of glass fiber added. The results showed that the addition of glass fiber significantly reduced workability without causing a significant impact on volume density and compressive strength The study concludes that glass fiber reinforcement is a promising solution to improve the flexural strength of lightweight expanded polystyrene concrete and make it suitable for load-bearing applications in construction.

Wind loads tests of external walls blocks masonry of noncombustible polystyrene concrete

Introduction. Blocks of non-combustible polystyrene concrete of D300 density grade, B1 compressive strength class with normalized thermal conductivity λ0 = 0,078 W/(m·°C) and frost resistance grade not lower than F75, developed by LLC “Institute VNIIZhelezobeton”, were used in masonry with a thickness of 375 mm without special fireproof lining. Such masonry successfully passed standard fire tests for fire hazard and fire resistance, which showed the possibility of its use in external non-bearing energysaving walls of multi-storey buildings (up to 25 floors inclusive, about 75 m high).Aim. Evaluation of the strength and deformation characteristics of non-combustible wall masonry made of noncombustible polystyrene concrete blocks with a density of D300 at design wind loads at a height of about 75 m. Materials and methods. Fragments of uncoated wall masonry 375 mm thick, 2,7 m high and 1,2 m wide of noncombustible polystyrene concrete blocks mounted on a mortar with over-all dimensions of 295 × 375 × 595 mm were tested.The test procedure is in accordance with State Standard 8829-2018.Results. The destructive bending load exceeded the calculated one by an average of 4,1 times, while the deflection in the middle of the fragment was 1,9 times less than the permissible one.A methodology has been developed for calculating the strength and deformability of masonry of polystyrene concrete blocks under wind loads, taking into account the influence of horizontal and vertical masonry joints, which is scheduled to be reflected in Amendment No. 1 SP 434.1325800.2018.Conclusions. The results of wind load tests showed that for unlined masonry made of non-combustible polystyrene concrete blocks with a density of D300 and a thickness of 375 mm, the requirements for strength and deformability are met with a significant margin. The results of tests for wind and fire effects of the specified block masonry make it possible to use it in nonbearing external walls of multi-storey residential energyefficient buildings up to 75 m high in virtually all regions of Russia.

Long-term thermal productivity of polystyrene concrete in a new composite wall in a fixed formwork

Purpose. Determination of the term of long-term thermal productivity of expanded polystyrene concrete in a new composite frame wall in a fixed formwork. Methodology. Methods of analysis and synthesis were used to conduct a patent search and develop a research methodology. The search was conducted using the patent database of Ukrainian Institute of Scientific and Technical Expertise and Information. Experimental studies were carried out in accordance with State Standard of Ukraine B V.2.7-38-95. The essence of the experiment consisted in reproducing the natural conditions of the “freeze-thaw-heat” cycle and measuring the thermal insulation characteristics of the main insulating material – polystyrene concrete – before and after the tests. Based on this, a conclusion was made about the long-term thermal productivity of the expanded polystyrene concrete in a new composite wall in the fixed formwork. The calculation of the dependence of thermal productivity on the number of cycles was carried out by arithmetic means using standard methods and programs such as Microsoft Excel. Findings. New technical solution of a composite wall made of expanded polystyrene concrete in a fixed formwork using light steel thin-walled structures has been created. A methodology for researching the long-term thermal productivity of this composite wall has been developed. An experimental study was conducted to research the influence of cyclic temperature changes (“freeze-thaw-heat”) on the long-term thermal productivity of the main heat-insulating element of the composite wall – expanded polystyrene concrete. An appropriate analytical model of the dependence of long-term thermal productivity of expanded polystyrene concrete samples on the number of “freeze-thaw-heat” cycles was calculated. The possibility of effective operation of the structure was confirmed by checking the normative values of the resource index and the factor of climatic destruction influence of materials during operation on their long-term thermal productivity. Implementation of a new composite wall solution in construction was conducted. Originality. For the first time, the dependence of cyclic temperature effects on the long-term thermal productivity of expanded polystyrene concrete in a new composite wall made in a fixed formwork using light steel thin-walled structures was determined, which made it possible to establish its effective operation life. This scientific result makes it possible to reduce material consumption, ensure economy, increase operational reliability and energy-efficient properties, and increase the service life of the composite wall. Practical value. New solution for installing a composite wall made of expanded polystyrene concrete in a fixed formwork using light steel thin-walled structures was developed and its effective thermal operation within the legally established term was substantiated. The period of effective exploitation of expanded polystyrene concrete as the least durable component of a composite wall is substantiated. Approbation of this design was carried out by installing it on a real construction site, which showed an increase in the manufacturability of construction processes compared to traditional enclosing structures.

The Influence of Addition of Fly Ash from Astana Heat and Power Plants on the Properties of the Polystyrene Concrete

Due to the constant increase in prices for energy resources, as well as the reduction in non-renewable resources in most developed countries of the world, the energy consumption standards of buildings are constantly decreasing, and the requirements for the level of thermal insulation of building envelopes are increasing. The increasing requirements in the level of thermal insulation of enclosing structures make the issues of improving and developing new materials and products become more urgent. Polystyrene concrete has good high-thermal and sound-absorbing properties. This serves as a means of reducing costs, improving thermal insulation, reducing the dead load (weight) on the building and outside, among many other advantages. However, concrete made with polystyrene foam as a substitute for large aggregates has insufficient strength, due to the fact that the cement has low adhesion to the polystyrene foam. Based on the research of scientists and authors on the possibility of using industrial waste, it was assumed that the addition of fly ash to the composition would strengthen the matrix and the degree of compression of the polymers by the cement matrix as a result of the presence of nanoparticles in the fly ash and their positive effect on the structure and properties of the composition. The aim of the study was to develop a heat-insulating polystyrene concrete based on a binder using fly ash and to investigate its physical and technical properties. The properties of fly ash have been studied for the purpose of safe use in mixtures to increase strength properties and improve adhesion to polymers. The involvement of industrial waste from the ashes of coal from Kazakhstani deposits will contribute to the ecological improvement of the environment of the megacities of Kazakhstan. The effect obtained from the optimal combination of the characteristics for a building material is the improved physical and mechanical properties of heat-insulating materials.

A New Type of Mineral Admixture and Its Impact on the Carbonation Resistance of EPS Concrete

In this study, the effect of microbead dosages (0%, 5%, 10%, 15%, and 20%) on the carbonation resistance of expanded polystyrene (EPS) concrete was investigated. Five groups of EPS concrete specimens were produced and underwent rapid carbonation testing. The carbonation depth and strength after carbonation of the specimens were measured at different carbonation ages (7 days, 14 days, and 28 days) and analyzed to determine the effect of microbead dosages and compressive strength on carbonation resistance. Results indicated that the carbonation depth increased with the progression of carbonation time. The introduction of microbeads was found to significantly improve the carbonation resistance of EPS concrete, leading to a reduction in carbonation depth of over 50% after 28 days and an increase in strength after carbonation by 18–56%. A relative compressive strength model for EPS concrete after carbonation was developed, which could accurately characterize the growth of compressive strength. Based on the analysis of EPS concrete carbonation depth data, a prediction model for the carbonation depth of EPS concrete with microbead dosage was established through fitting, providing improved accuracy in predicting carbonation resistance. The microstructure of EPS concrete was also examined using scanning electron microscopy to uncover the underlying mechanisms of microbead enhancement on carbonation resistance. These findings have potential implications for future research and engineering applications in the carbonation resistance of EPS concrete.

Early-age mechanical properties and constitutive model of polystyrene concrete under impact load

The dynamic mechanical tests of polystyrene concrete with ages of 12 h, 24 h and 36 h and 28 d were carried out by Φ 100 mm SHPB equipment. The effects of strain rate and age on dynamic mechanical properties of polystyrene concrete were analyzed in terms of the relationship between strain rate and impact velocity, strength characteristics, deformation characteristics and energy absorption characteristics. And based on Saenz model, the early-age dynamic constitutive model of polystyrene concrete was constructed. The results show that the strain rate of polystyrene concrete is positively correlated with the impact velocity. At the same impact velocity, the strain rate of polystyrene concrete decreases with age. The strength characteristic indicators, deformation characteristic indicators and energy absorption characteristic indicator of polystyrene concrete all have strain rate strengthening effect, and all these indicators and the strain rate sensitivity of these indicators increase with age. Polystyrene concrete has good deformation and energy absorption characteristics at early age. At the age of 36 h, the peak strain, ultimate strain and specific energy absorption of polystyrene concrete can reach 77∼80%, 95∼106% and 86∼92% of that at the age of 28 d, respectively. The constructed dynamic constitutive model is reasonable and reliable, and it can be used to describe the mechanical behavior of polystyrene concrete at early age under impact load.

Production technology and properties of polystyrene concrete on recycled polystyrene

The article deals with the production of polystyrene concrete from recycled polystyrene crushed in a rotary crusher waste from the production of foam packaging. The resulting polystyrene concrete can be attributed to thermal insulation, used for insulation of load-bearing structures of buildings, as well as to structural and thermal insulation, used as a bearing layer of the outer walls of low-rise buildings. The dependence of the thermal conductivity of the sample on the density and strength of polystyrene concrete has been established, and the resistance to shock loads depends not only on the composition but also on the polystyrene concrete hardening accelerator used.

Homogenization approach for estimating the effective thermal conductivity of Lightweight Expanded Polystyrol Concrete

This paper aims to determine the macroscopic thermal conductivity coefficient of Lightweight Expanded Polystyrene Concrete (LEPS-C) using the homogenization approach through analytical calculations. The influence of expanded polystyrene on the overall thermal conductivity coefficient of LEPS-C was determined using classical homogenization models based on the solution of the Eshelby problem, with the matrix phase being concrete and the inclusion phase being expanded polystyrene particles randomly distributed in the matrix phase. The content of substituted expanded polystyrene particles was varied from 0% to 40% by volume of concrete. The analytical calculation results obtained from the homogenization models were compared with the experimental results, showing good agreement and demonstrating the efficacy of the homogenization method in predicting the macroscopic thermal conductivity of LEPS-C.

Technology for erecting monolithic enclosing structures of buildings made of expanded polystyrene concrete

This work aims to develop effective technology for erecting monolithic enclosing structures of buildings made of expanded polystyrene concrete. As a result of the research carried out, a model of large-panel formwork made of ABS plastic for concreting monolithic walls with an expanded polystyrene concrete mixture was developed, representing rectangular panels of a size of 3000 x 1200 x 40 mm. To ensure the necessary strength and rigidity, the outer side of the formwork is made cellular with a large number of longitudinal and transverse stiffeners placed in increments of 300 mm. We have developed a technology for erecting monolithic enclosing structures of buildings made of expanded polystyrene concrete using a mobile concrete-mixing unit. The following are technical and economic indicators for manufacturing monolithic walls out of expanded polystyrene concrete of a volume of 46 m3 : the cost is 354.784 thousand rubles, and the labor intensity and unit capacity are 163.76 people.*h and 27.36 units.*h, respectively. The results significantly offer the construction industry a solution to reduce the labor intensity of construction and installation while manufacturing cost-effective monolithic enclosing structures for buildings.

EVALUATION OF THE NEW CONSTRUCTIVE-TECHNOLOGICAL SOLUTION OF THE FENCE STRUCTURE IN THE NON-REMOVABLE FORMWORK

The known constructive and technological solutions of enclosing constructions of buildings in fixed formwork with the use of qualitative, quantitative and general analysis are analyzed. Selected quantitative indicators, such as wall thickness, weight of 1 m2 of wall, heat transfer resistance, area of premises, cost, durability, tendency to shrinkage. Qualitative indicators were used: resistance to the sun, mold, fertilization and destruction, features of delivery of building materials. The method of multicriteria analysis is used to evaluate new structural and technological solutions of fencing structures and determine the most effective technologies. Categories of various constructive-technological decisions in a fixed timbering on the basis of economic consideration of modeling are considered. Such modern constructive-technological decisions of enclosing constructions in a fixed timbering are selected for comparison, as: expanded polystyrene blocks; blocks with wall alignment system; polystyrene concrete blocks; concrete blocks; blocks of cement-chip material; large panels made of expanded polystyrene; three-layer reinforced expanded polystyrene panels; cement particle boards; concrete slabs; frame-monolithic formwork with cement-chipboard cladding; frame-monolithic formwork with cladding of glass-magnesium plates and technology according to the patent UA 149402. The new design and technological solution, which has been developed and patented, is a combination of modern materials that are of great interest and demand to consumers, such as light steel thin-walled structures and expanded polystyrene concrete. The evaluation of technological solutions by quantitative criteria on a ten-point scale, where the minimum and maximum values are assigned points 1 and 10, respectively. Graphical modeling of the summary variants, which are equalized, is performed, and the corresponding diagrams are constructed.

ИССЛЕДОВАНИЕ ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ УСТРОЙСТВА И РЕМОНТА ОСНОВАНИЙ ПЛОСКИХ КРОВЕЛЬНЫХ ПОКРЫТИЙ

In the practice of modern construction, light concretes of low thermal conductivity are used as a heat-insulating layer of enclosing structures. In particular, they are used for warming flat roofs of buildings for various purposes. One of the effective methods of thermal insulation is the use of polystyrene concrete of low average density and thermal conductivity directly in construction conditions. Research has established a rational selection of the composition of this type of concrete for the installation of a monolithic heat-insulating layer, resource support for the technological process, including mechanization of work and qualification requirements for performers. Improvement of organizational and technological solutions for flat roofs based on the choice of rational parameters of technological processes and operations provides a reduction in labor intensity, duration and cost of work at the construction site. Comparison of technologies for the installation of roofing bases from deposited materials according to technical and economic parameters.

The synergistic strengthening effect of silane coupling agent on the interface between PVA/EPS and cement: experiment and molecular simulation

ABSTRACT Expanded polystyrene (EPS) concrete is a new type of green building material. To make it more widely used, in this work, polyvinyl alcohol (PVA) fiber and silane coupling agent (SCA) were used to toughen it. The synergistic enhancement mechanism of SCA on PVA/cement and EPS/cement interfaces was systematically investigated from macro mechanical properties, microstructure characteristics, and nano interface interaction. Firstly, based on the mechanical property test, it was found that the introduction of SCA and PVA fibers can significantly improve the flexural strength of EPS composite concrete at 7 and 28 days, followed by the compressive strength. Secondly, the cut pieces of corresponding composite concrete were observed by electron microscope. It was found that SCA made the two interfaces more closely, and its bonding effect at the micro interface was described. Finally, molecular dynamics (MD) was used to model PVA/C-S-H and EPS/C-S-H with or without SCA. Then, the local structure, dynamic performance, and binding energy of the interface were calculated and analyzed. The analysis results showed that SCA reduced the interface effect and enhanced the interface hydrogen bonding, van der Waals interaction, Ca-H coordination bond and stability. Thus, the interfacial adhesion energy was improved, and the weak interfacial bonding between organic polymers (PVA, EPS) and inorganic silicates (C-S-H) was enhanced.

Study on frost resistance of EPS concrete based on EPS beads wrapping modification

Expanded polystyrene (EPS) concrete is an ideal low carbon green building material, but the frost resistance is weak in natural environment, which hinders the popularization of EPS concrete. In this study, magnesium phosphate cement (MPC), ultra-high performance concrete (UHPC), and waterborne polyurethane (WPU) were used to wrap the surface of EPS beads and enhance its concrete performance. The frost resistance durability of four groups of EPS concrete was studied, the uniaxial compression tests of concrete after freezing and thawing were conducted, the results show that: the freeze thaw damage law of EPS concrete is different from ordinary concrete, the standard of freeze-thaw failure of EPS concrete is the sudden increase of dynamic elastic modulus but not continues decreasing, the mass of EPS concrete increases but not decreases; concrete with EPS beads wrapped by UHPC and WPU has good frost resistance, the frost resistance level has been increased by 100 levels and the service life increased by 60% than that of EPS beads unwrapped, the strength-degradation is much slower than that of concrete without wrapped; after freeze-thaw failure, the cracks and the interface transition zone (ITZ) gap of concrete with EPS beads wrapped is smaller than unwrapped, the macro phenomenon of freeze-thaw failure is explained from the micro level, based on macro and micro test results, the degradation mechanism of concrete with EPS wrapped and unwrapped under the action of freezing-thawing cycles are discussed. Beside, the stress-strain curves of EPS concrete after freeze-thaw attenuation were studied, the attenuation of concrete with EPS beads wrapped with WPU and UHPC is not serious as the concrete with EPS unwrapped, the proposed stress-strain model is in good agreement with the experimental results, which can provide a reference for evaluating the mechanical properties of EPS concrete after freeze-thaw. Finally, it is suggested to use linear segment and curve segment to describe the attenuation trend of relative dynamic elastic modulus, the fitted model is in good agreement with the experimental results, it can provides a reference for the study of freeze-thaw mechanical properties and the prediction of freeze-thaw cycle of this kind of concrete.