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The dispersion of nano‐SiO2 (NS) in cement plays a critical role in enhancing the properties of cementitious materials. In this study, the combination of ultrasonic dispersion and polycarboxylic acid water reducing agent (PCE) was used to significantly improve the dispersion of NS. The effects of ultrasonic dispersion time, NS content, and PCE content on dispersion quality were investigated, alongside their impact on mechanical properties, electrical resistivity, and frost resistance. The results demonstrated that this synergistic method optimized the dispersion of NS, leading to superior mechanical properties and frost resistance. With an ultrasonic dispersion time of 40 min, NS content of 1.0 wt.%, and PCE content of 0.75 wt.%, the cement paste achieved its optimal performance. Compared to non‐dispersed samples, compressive strength increased by 33.7%. After 75 freeze–thaw cycles, the mass loss was 2%, the relative dynamic elastic modulus was 99.15%, and the strength loss was 13.74%. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable construction practices, the utilization of recycled concrete has emerged as a pivotal strategy, distinguished by its commitment to resource conservation and environmental stewardship. Nevertheless, the inherent micro-porosity and micro-cracking within the old mortar of recycled concrete may lead to weak bonding performance at the interfacial transition zone, culminating in diminished strength, reduced density, and elevated water absorption rates compared to conventional concrete, which critically impairs its performance in cold climates subjected to freeze-thaw cycles. Consequently, this paper provides a structured examination of the frost resistance properties of recycled concrete subjected to freeze-thaw cycling. Initially, the study delineates the mechanisms of frost-induced damage in recycled concrete by synthesizing the degradation pathways observed in both conventional and recycled concrete during freeze-thaw exposure. Subsequently, a detailed analysis is conducted to identify the pivotal factors affecting frost resistance, encompassing the proportion and moisture affinity of recycled aggregates, the addition of silica fume and fly ash, the water-to-cement ratio, and the degree of water saturation. In the final segment, the study compiles and reviews the strategies for bolstering the frost resistance of recycled concrete, including the incorporation of air-entraining admixtures, fiber reinforcement, and aggregate modification approaches. The objective of this research is to offer a thorough comprehension of recycled concrete, with a concentration on the mechanisms of frost damage, the critical determinants of frost resistance, and interventions to augment its resilience against freezing conditions. On this basis, the present paper, in conjunction with the characteristics and current research status of recycled concrete, proposes recommendations for the application of recycled concrete in cold regions. This review is anticipated to facilitate researchers in gaining a comprehensive understanding of the freeze-thaw characteristics of recycled concrete and the measures to enhance its frost resistance. Furthermore, it aims to assist engineering and technical personnel in selecting appropriate treatment methods to improve the frost resistance of recycled concrete in cold regions, thereby promoting the practical engineering application of recycled concrete in such areas. [ABSTRACT FROM AUTHOR]

In order to increase the suitability of coarse recycled concrete aggregates and improve the frost resistance of recycled coarse aggregate concrete, this study aims to investigate the effects of an antifreeze-type water-reducing admixture, air-entraining admixture, and antifreeze admixture on the frost resistance of recycled coarse aggregate concrete. The effectiveness of these admixtures is gauged by the mass loss rate and the relative dynamic modulus of elasticity (RDM). Mercury-impressed porosimetry (MIP), super depth of field microscopy, and scanning electron microscopy (SEM) were employed to characterize the hydration products, microstructure, and pore structure of recycled coarse aggregate concrete, with a view to establishing a connection between the microstructural characteristics and the macro properties and analyzing the micro-mechanism of the improvement effect of frost resistance. The test results demonstrate that the admixtures have a significant impact on the frost resistance of recycled coarse aggregate concrete. In particular, the recycled coarse aggregate concrete with an antifreeze admixture (dosage of 1%) and a water–cement ratio of 0.41 exhibited a mass loss of only 1.23% after 200 freezing and thawing cycles, a relative dynamic modulus of elasticity of up to 93.97%; however, the control group had reached the stopping condition at 150 freeze–thaw cycles with more than 10% mass loss. The recycled coarse aggregate concrete with added antifreeze admixture had a tight connection between the aggregate and the paste and a more pronounced improvement in the pore structure, indicating excellent resistance to frost damage. [ABSTRACT FROM AUTHOR]

The contents of waste glass powder (WGP) (0%, 10%, 15%, 20%, 25%) and water-binder ratio (W/C) (0.24, 0.26, 0.28) were used as influencing factors, and the quality loss rate (Δm) and compressive strength loss rate (Δfc) were used as characterization parameters. The Ca/Si ratio and main element contents of C-S-H gels with different WGP content were investigated by energy dispersive spectrometry (EDS). The pore structure evolution characteristics of WGP composite cementing materials were investigated by low field nuclear magnetic resonance (NMR). Using Δfc as the index of frost resistance degradation and Weibull function, the frost resistance degradation of glass doped pervious concrete (WGP-PC) was modeled. The results show that, with WGP, for the same number of cycles, Δm and Δfc decrease and increase with the increase of WGP. Under the same WGP content, Δm and Δfc decrease first and then increase with the increase of W/C. After 100 freeze-thaw cycles, the samples with WGP content of 20% and W/C of 0.26 have the best freeze-resistance. Microscopic tests show that with the increase of WGP content, the Ca/Si ratio of C-S-H gel decreases at first and then increases with the increase of WGP content. The extreme value of Ca/Si is 2.36 when WGP is added by 20%. The pore volume of hardened paste with 20% WGP content decreased by 18.6% compared with that of cement system without WGP. The overall compactness of the specimen was improved. On the basis of the test data, a life prediction model was established according to Weibull function. The experiment showed that Δfc could be used as a durability degradation index, and the slope of the reliability curve became gentle after WGP was added, which reduced the damage degradation rate of PC. W/C was 0.26. It's about 5 000 hours. [ABSTRACT FROM AUTHOR]

In order to rationalize the consumption of graphite tailing sand and reduce its pollution of the environment—with sodium silicate being a commonly used activator for improving the strength of concrete composites—in this study, the joint effects of sodium silicate (SS) and graphite tail sand (GT) on the strength and frost resistance of graphite tail sand high-performance mortar (GT-HPM) were investigated. Experiments were conducted to evaluate the bulk density, water absorption, compressive strength, speed of sound, and working performance status of GT-HPM before and after freezing and thawing at different SS dosages and different GT substitution rates. The microstructural properties of GT-HPM were also analyzed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM/EDS). The results showed that 4% SS doping improved the performance of GT-HPM more obviously. Moreover, with an increase in the GT substitution rate, the mechanical properties and frost resistance of GT-HPM increased firstly and then decreased, and the best performance of GT-HPM was obtained when the GT substitution rate was 20%. At 6% SS doping, the performance of GT-HPM gradually decreased with the increase in the graphite tailing sand substitution rate. FT-IR testing showed that there was no significant change with the type of hydration products used, and the Si–O–T absorption peak and average bond length of GT-4 were the largest. SS and GT promoted the generation of hydration products. Microstructural analysis showed that 4% SS promoted the hydration reaction; in addition, an appropriate amount of GT improved the pore structure of HPM, increased the strength and frost resistance, and provided fundamental insights for the subsequent comprehensive utilization of graphite tailing sand. [ABSTRACT FROM AUTHOR]

In this paper, the effect of basalt fiber (BF) on the frost resistance of concrete under different curing conditions was investigated, and its frost resistance mechanism was analyzed. Three different curing conditions (normal curing, short-term curing, and seawater curing) were adopted, and concrete with different BF volume contents was designed. Freeze-thaw (FT) tests were carried out using the rapid freezing method to test the frost resistance of basalt fiber reinforced concrete (BFRC). Additionally, the mass loss rate (MLR), relative dynamic modulus of elasticity (RDME) change, and compressive strength reduction of specimens during the freeze-thaw cycles (FTCs) were evaluated. The results show that when the BF content is 0.15%, under normal curing, short-term curing, and seawater curing conditions, the residual compressive strength of BFRC after FTCs was increased by 5.4%, 28.1%, and 30.9%, respectively, compared to plain concrete. By incorporating BF into concrete, the development of microcracks can be effectively retarded, and damage generation during FTCs can be reduced. In addition, the microscopic morphological characteristics and pore structure characteristics of concrete further elucidate the frost resistance mechanism of BFRC from a microscopic perspective. [ABSTRACT FROM AUTHOR]

Polyvinylpyrrolidone (PVP) was used as a dispersant and combined with ultrasonic technology to disperse multi walled carbon nanotubes(MWCNTs). A water-based dispersion of MWCNTs was prepared, and it was used as a doping phase to prepare fly ash concrete. The influence of multi walled carbon nanotube content on the mechanical and durability properties of fly ash concrete was studied through TEM, XRD, SEM, FT-1R, mechanical performance testing and rapid freeze-thaw experiments. The results indicated that PVP combined with ultrasonic technology could effectively disperse MWCNTs, and the addition of MWCNTs to fly ash concrete could accelerate the cement hydration reaction and increase the generation of hydration products such as C-S-H and Ca(OH)2. Moderate doping of MWCNTs could refine the internal pore structure of cement, reduce the number of cracks and large-sized pores, and transform the failure mode of fly ash concrete from brittle fracture to ductile fracture. The peak load and deformation of the MWCNTs-0.3 % specimen reached their maximum values, which were 41.6 kN and 2.92 mm, respectively. The compressive strength and flexural strength reached their maximum values, which were 60.5 and 11.2 MPa, respectively. After 100 rapid freeze-thaw cycles, the mass loss rate of the MWCNTs-0.3 % sample was the lowest value of 0.271 %, and the maximum relative dynamic elastic modulus was 84.34%, indicating a significant improvement in frost resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Conductive hydrogels prepared by electrohydrodynamic printing exhibit enhanced conductivity. • Ion-electron conductive hydrogel with MXene co-ILs composite conductive network. • Hydrogel exhibited good mechanical properties, excellent sensing performance, and high frost resistance. • Hydrogel-based flexible strain sensor for human motion detection and information transmission. Conductive hydrogels with high performance and frost resistance are essential for flexible electronics, electronic skin, and soft robots. Nonetheless, the preparation of hydrogel-based flexible strain sensors with rapid response, wide strain detection range, and high sensitivity remains a considerable challenge. Furthermore, the inevitable freezing and evaporation of water in sub-zero temperatures and dry environments lead to the loss of flexibility and conductivity in hydrogels, which seriously limits their practical application. In this work, ionic liquids (ILs) and MXene are introduced into gelatin/polyacrylamide (PAM) precursor solution, and a PAM/gelatin/ILs/MXene/glycerol (PGIMG) hydrogel-based flexible strain sensor with MXene co-ILs ion–electron composite conductive network is prepared by combining the electrohydrodynamic (EHD) printing method and in-situ photopolymerization. The introduction of ILs provides an ionic conductive channel for the hydrogel. The introduction of MXene nanosheets forms an interpenetrating network with gelatin and PAM, which not only provides a conductive channel, but also improves the mechanical and sensing properties of the hydrogel-based flexible strain sensor. The prepared PGIMG hydrogel with the MXene co-ILs ion–electron composite conductive network demonstrates a tensile strength of 0.21 MPa at 602.82 % strain, the conductivity of 1.636 × 10−3 S/cm, high sensitivity (Gauge Factor, GF = 4.17), a wide strain detection range (1–600 %), and the response/recovery times (73 ms and 74 ms). In addition, glycerol endows the hydrogel with excellent freezing (−60 °C) and water retention properties. The application of the hydrogel-based flexible strain sensor in the field of human motion detection and information transmission shows the great potential of wearable devices, electronic skin, and information encryption transmission. [ABSTRACT FROM AUTHOR]

In this paper,the influence of fly ash and silica fume on the compressive strength,flexural strength and frost resis tance of cement mortar after ultra-low temperature freeze-thaw cycle(-190-20 )was studied under different dosage of fly ash and silica fume. The results show that the deterioration degree of cement mortar after ultra-low temperature freeze-thaw cycle is much greater than that of low temperature freeze-thaw cycle(-20-20 ). Among them,when the double-doped fly ash is mixed with 15% and the silica fume is mixed with 10%,the mechanical performance of cement mortar is the best. After 10 super-low temperature freeze-thaw cycle,the flexural strength and compressive strength reach 10.06 MPa and 38.29 MPa respectively. At this time,the loss rate of cement mortar strength is the lowest and the frost resistance is the best the pore size reaches a minimum of 33.15 nm,and the porosity is also a minimum of 13.58%. [ABSTRACT FROM AUTHOR]

Permeable concrete has the characteristics of breathability, permeability, and high heat dissipation. To improve its mechanical and frost resistance properties, this study optimized the preparation and performance of permeable concrete by adding materials to improve its performance. The performance analysis validate that epoxy resin owns a filling effect on the pores of permeable concrete. The internal curing agent, high water absorbent resin, has a good water absorption effect. The synergistic effect of these two increases the density and compressive strength of permeable concrete. When the two contents are 0.5%, the maximum compressive strength of modified permeable concrete at 7 and 28 days was 15.62 and 17.97 MPa, respectively. Under the action of freeze-thaw cycles, its mass loss rate show an upward trend By comparison, epoxy resin and high water absorbent resin are beneficial for improving the frost resistance of permeable concrete. The minimum value of relative dynamic modulus of elasticity remains stable at over 80%, and the loss rate of dynamic modulus of elasticity is all below 0.4. However, the influence of epoxy resin and SAP on the mass loss rate is relatively small, and the mass loss of all experimental groups is controlled below 2.5%. The binomial Fourier function model is the best predictive model for permeable concrete under freeze-thaw cycles. This study has positive significance for improving the performance of permeable concrete and maintaining the sustainable development of ecological cities.

Introduction. The study was carried out to determine the possible causes of damage to the finishing plaster coverings on the facades of historical stone buildings, built in St. Petersburg before 1917, as a result of their humidification and subsequent frost destruction.Materials and methods. The mechanism of humidification of a homogeneous wall structure plastered on both sides due to the moisture transfer from the room to the environment through the wall thickness due to the difference in partial pressures of water vapour from inside and outside the room during the cold season is studied. The paper provides the graphs of the distribution of the actual and maximum partial pressures of water vapour over the thickness of the wall structure, depending on the type of plaster covering, for two calculated cases — for the conditions of the coldest month and the coldest five-day period in St. Petersburg.Results. It is revealed that for the conditions of the coldest month in St. Petersburg, the actual partial pressure of water vapour in the thickness of the wall structure under consideration does not exceed the maximum, which indicates the absence of conditions for moisture condensation in the thickness of the wall envelope. However, as the vapour permeability of the external plaster decreases, the curves of the distribution of the actual and maximum partial pressures converge at the interface of the stone base and the plaster covering. For the conditions of the coldest five-day period, the actual partial pressure of water vapour already at a distance of 135 mm from the inner surface exceeds the maximum partial pressure, which indicates a high risk of moisture condensation, and this risk is the higher the less vapour permeable the plaster covering is.Conclusions. It is proven that when the coldest outdoor temperatures are established, there is a high probability of condensation of water vapour in the thickness of the wall structure under consideration. The highest risk of freezing of the condensable moisture will be observed at the interface of stone base with the external plaster. Freezing of moisture in cracks and voids in the contact zone of the stone base and the plaster covering can lead to water trapping, the occurrence of significant internal stresses in the finishing layer and, as a result, to its gradual damage, up to the loss of individual fragments of plaster.

Frost damage on the concrete surface might be aggravated when freezing occurs in the presence of a salt solution, like sea water or de-icing salt. A possible mechanism behind this combination of frost and salt is discussed. When freezing takes place in pure water, ice formed at the surface will block inflow of water to the concrete, but it will cause drying of the concrete. When freezing occurs in salt solution, unfrozen water (brine) can enter the concrete surface and make the concrete completely saturated. When pore water freezes, it exerts pressure. The effect of air-entrainment is favourable since it reduces the stresses. A calculation is made of the air requirement for concrete with w/c-ratio 0.45.

Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate, and it is an important basic material for sponge city construction. The presence of a large number of connected pores inside pervious concrete leads to a marked difference in durability failure mechanism compared with that of ordinary concrete.In this study, the frost resistance and anti-clogging of pervious concrete were introduced in detail, and the methods to improve their performance were summarized systematically. The cracking pattern of pervious concrete is influenced by geometric characteristics and three-dimensional morphological features of pores, resulting in its crack generation, development, and geometry being significantly different from those of ordinary concrete, thus leading to different freeze-thaw cycle mechanisms. In addition, due to its different pore structure compared to ordinary concrete, three types of clogging mechanisms, affecting the long-term permeability of pervious concrete were elaborated systematically (i.e., physical clogging, biological clogging, and chemical clogging). And the ways to improve the anti-clogging of pervious concrete are systematically presented from multiple perspectives. Finally, in order to broaden the engineering applications of pervious concrete, some research proposals are presented in this study.

The examinations of concrete involved partial substitution of cement with Cement Kiln Dust (CKD - 0, 5, 10, 20 and 30%). The water/cement (w/c) ratio amounted to 0.36. The obtained findings pertaining to open porosity, density, and volumetric density were found to correlate with the capillary action and absorptivity of the analyzed types of concrete. With the maximum addition of CKD, i.e. 30%, open porosity decreased by 35%. In turn, CKD added in the amount of 5% resulted in a slightly reduced addition compressive strength, amounting to 1.3% and 2.1% following 28 days and 56 days of concrete curing, respectively. After 28 days, the differences in strength were greater when the additive was supplied in higher amounts, i.e. 10%, 20%, and 30%, resulting in 6.5%, 13.4%, and 22.9% decrease, respectively, in spite of strength improvement. In terms of flexural and splitting tensile strengths, comparable relations were noted. As far as the frost resistance test results are concerned, the mass losses in all examined concretes were not significant, reaching up to 0.5%. The strength reduction in the case of the first three series of concretes was below 3%. When the CKD addition was increased to 20% and 30%, the value of the dynamic modulus of elasticity Ec,s decreased to a greater degree, by 8.0% and 14.7%, respectively. The hydrophobization effect is best seen in CKD-free concrete. After the impregnation, the loss of mass following the frost test of the samples is reduced by half. With a higher CKD content, the hydrophobization effectiveness is insignificant. The most favourable results were observed for hydrophobization with the oligomer-based preparation A1.

In modern construction, one of the most important factors in the execution of contracts is time. Standard procedures for assessing the frost resistance or concrete are usually very time‐consuming and can take up to 40 days. The current paper is experimentally and practically oriented. It presents an alternative testing method, based on air void network, that allows to assess the frost resistance of concrete within just a few days of taking the samples. X‐ray micro‐CT scans were introduced to obtain the quantitative and qualitative 3D information about the air void microstructure taking into account total air content: A (%), pores of the size below 300 μm in diameter content: A300 (%), specific surface of air voids: α (mm−1) and spacing factor: L (mm) to predict the freeze/thaw durability. To verify the assumptions of the frost resistance method, based on the analysis of pore microstructure, tests of freeze/thaw resistance in accordance with Polish supplement to European Standard were carried out. Presented research revealed that the appropriate microstructure of air pores, in particular, content of micropores with the diameter less than 0.3 mm: A300 combined with a spacing factor: L (mm) can constitute a reliable basis for determining concrete freeze/thaw durability. Thus, the method proposed in the current paper can be effectively used for fast and trustworthy determination of the air‐entrained concrete durability in a short time and without any special preparation of the tested sample that allows immediate preventive or repair actions to be taken if required. [ABSTRACT FROM AUTHOR]

In recent years, applying slag micro-powder as a substitute for cement in preparing alkali-activated slag cement stabilized sand (AASCSS) mixtures has become increasingly widespread. In the severe cold regions of Xinjiang, multi-objective optimization of the mechanical and frost resistance properties of AASCSS is particularly crucial. This paper adopts slag micro-powder to replace Portland cement, together with lime and desulfurization gypsum as activators, to explore the effects of activator type and dosage on the mechanical and frost-resistance properties of AASCSS. A prediction model for the mechanical and frost-resistance properties of AASCSS based on projection-pursuit regression (PPR) was proposed and established. Using the developed PPR model, contour plots of the comprehensive performance were calculated, simplifying the multi-objective problem into two single-objective problems focusing on mechanical and frost resistance properties for analysis. This method avoids subjective weighting and hypothesis-based modeling. By analyzing the contour plots of comprehensive performance, the optimal performance indices for mechanical and frost–thaw properties and the corresponding types and dosages of activators can be directly determined. When the required 7-day unconfined compressive strength in road engineering is 5.6 MPa, the optimal value of the freeze–thaw performance index (BDR) is 94.08%. At this point, the corresponding lime content is 2.1%, and the desulfurization gypsum content is 3.3%. The research results provide a reference for applying slag to road-based materials. [ABSTRACT FROM AUTHOR]

This paper describes the research on micro-silica, popular in Kazakhstan ferrosilicon production technogenic waste, its impact on self-compacting concrete rheological and physical-engineering properties, and performance and durability improvement of building structures made of this concrete type utilizing volumetric fiber reinforcement. The paper includes the results of laboratory and industrial tests of self-compacting concrete mixtures (SCC) strength and operational properties. The most effective ratio of micro-silica as a filler in the binder and the optimal amount of low-modulus polypropylene fiber was selected to manufacture high-quality selfcompacting concrete of C25/30, C30/35, C35/40, C40/45 classes produced using local raw materials. Examples of compositions using micro-silica confirm the possibility of up to 20% cement consumption reduction and increase the concrete frost resistance to F340, reduction of self-compacting concrete volumetric water absorption by up to 30%, increase bending strength by up to 35% with the combined use of silica and polypropylene fiber in a right proportion are described here. The research results provide practical value for self-compacting and cast concrete Kazakhstani manufacturers. [ABSTRACT FROM AUTHOR]

Selective demolition of building components and recycling construction demolition waste is a growing tendency as we move towards a circular construction. This study investigates the feasibility of using demolition waste from calcium silicate brick masonry as an aggregate in concrete and mortar. The purpose is to assess its impact on concrete and mortar properties, including compressive strength, durability, and workability. Silicate bricks from two demolished buildings were processed into aggregate, and laboratory experiments were conducted to evaluate concrete and mortar made with varying proportions of recycled aggregate. Results indicate that replacing natural aggregate (limestone rubble and sand) with recycled silicate brick aggregate up to 50% does not significantly compromise concrete performance, with no significant decrease in compressive strength observed. Frost resistance of the concrete made with recycled aggregate even surpasses that of reference concrete, possibly due to the lower density and higher (closed) porosity of the recycled aggregate. However, challenges such as increased water demand and loss of workability over time are noted with higher proportions of recycled aggregate. Further research is recommended to explore strategies for mitigating these challenges and to assess the effects of chemical admixtures on concrete properties. Overall, the findings suggest that recycled calcium silicate brick holds promise as a sustainable alternative for aggregate in concrete production. [ABSTRACT FROM AUTHOR]

Improvement of hydrophysical properties and corrosion resistance of self-compacting concrete to the effects of alternate freezing–thawing and aggressive soils of Southern and Central Kazakhstan is of interest to a wide range of researchers from the side of practical application of the obtained results in construction practice. It is proposed to form a spatially reinforced fine crystalline structure of a cement matrix with the maximum dense packing by using a complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) in the composition of self-compacting concretes (SCCs). The introduction of the calculated amount of the above additives increases the operational reliability of the current SCC compositions, increasing the water resistance to W16, frost resistance to F = 500, increasing the compressive strength by 20%, and reducing the mass loss of samples during corrosion leaching to 50%. It has been experimentally established that the proposed addition of the complex modifier (hyperplasticizer + polymer + microsilica + fibro fibers) to the SCC composition allows obtaining self-compacting concrete of high quality with improved performance characteristics (compressive strength, water resistance, frost resistance, and corrosion resistance). Studies have shown that the complex modifier-modified SCC compositions have a high degree of resistance in aggressive environments and leaching corrosion. Based on the results of the conducted tests, it is possible to recommend the obtained SCC compositions for the production of building products working in the zone of alternating freezing–thawing and aggressive soils. [ABSTRACT FROM AUTHOR]

Polypropylene fiber was used as the reinforcing phase to prepare polypropylene fiber modified porous ecological concrete. The effect of fiber doping on the microstructure, mechanical properties, and frost resistance of the concrete was studied. The results showed that the appropriate amount of polypropylene fibers were tightly wrapped in the concrete matrix after being doped into the porous ecological concrete, forming a stable fiber network structure inside the concrete, which improved the bond strength between the coarse aggregates of the concrete, enhanced the resistance to deformation, and reduced the phenomenon of cracks and aggregate detachment. When the doping amount of polypropylene fiber was 0.9 vol%, the compressive strength, flexural strength, peak stress and deflection of concrete all reached their maximum values, which were 29.95, 5.04, 28.00 MPa, and 6.8 mm, respectively. The residual bearing capacity of concrete decreased in the order of PP-0.9% > PP-0.6% > PP-0.3% > PP-1.2%. After 150 rapid freeze-thaw tests, with the increase in the amount of polypropylene fiber doping, the concrete quality loss first decreased and then increased, and the relative dynamic elastic modulus first increased and then decreased. When the amount of polypropylene fiber doping was 0.9 vol%, the minimum concrete quality loss rate was 1.38%, and the maximum relative dynamic elastic modulus was 90.45%. From the comprehensive analysis, it can be concluded that the mechanical properties and frost resistance of concrete with a polypropylene fiber doping content of 0.9 vol% are the best. [ABSTRACT FROM AUTHOR]

In this paper, fiber Bragg grating (FBG) sensors were applied to investigate the frost resistance of C60 concrete. First, the growth of both the static and dynamic elastic modulus of C60 concrete with curing age was investigated using an FBG, the standard method, and the resonance method, respectively. Second, to simulate the freezing and thawing conditions in cold regions, the concrete specimens were subjected to air freezing and water thawing using the slow freezing method. The authors explored the effect of freeze–thaw cycles on the mechanical properties of concrete and established a mathematical model relating its mechanical properties to freeze–thaw cycles based on an FBG sensor. Meanwhile, its compressive strength, dynamic elastic modulus, and mass loss rate were tested. Finally, the interface morphology and hydration products of concrete were observed using a scanning electron microscope (SEM) after freeze–thaw cycles. The results indicate that both the static and dynamic elastic modulus of C60 concrete increase with curing age. Its elastic modulus measured by FBG is approximately the same as that measured by the standard method, confirming the viability of using an FBG sensor to measure its elastic modulus. Furthermore, the authors highlighted the dependence of its compressive strength on the freeze–thaw cycles. The relationship of the static elastic modulus to freeze–thaw cycles is similar to that of the dynamic elastic modulus and mass loss rate. A static elastic modulus achieved from an FBG is proposed here to characterize the frost resistance of C60 concrete. [ABSTRACT FROM AUTHOR]

In the pursuit of sustainable construction practices, the utilization of recycled concrete has emerged as a pivotal strategy, distinguished by its commitment to resource conservation and environmental stewardship. Nevertheless, the inherent micro-porosity and micro-cracking within the old mortar of recycled concrete may lead to weak bonding performance at the interfacial transition zone, culminating in diminished strength, reduced density, and elevated water absorption rates compared to conventional concrete, which critically impairs its performance in cold climates subjected to freeze-thaw cycles. Consequently, this paper provides a structured examination of the frost resistance properties of recycled concrete subjected to freeze-thaw cycling. Initially, the study delineates the mechanisms of frost-induced damage in recycled concrete by synthesizing the degradation pathways observed in both conventional and recycled concrete during freeze-thaw exposure. Subsequently, a detailed analysis is conducted to identify the pivotal factors affecting frost resistance, encompassing the proportion and moisture affinity of recycled aggregates, the addition of silica fume and fly ash, the water-to-cement ratio, and the degree of water saturation. In the final segment, the study compiles and reviews the strategies for bolstering the frost resistance of recycled concrete, including the incorporation of air-entraining admixtures, fiber reinforcement, and aggregate modification approaches. The objective of this research is to offer a thorough comprehension of recycled concrete, with a concentration on the mechanisms of frost damage, the critical determinants of frost resistance, and interventions to augment its resilience against freezing conditions. On this basis, the present paper, in conjunction with the characteristics and current research status of recycled concrete, proposes recommendations for the application of recycled concrete in cold regions. This review is anticipated to facilitate researchers in gaining a comprehensive understanding of the freeze-thaw characteristics of recycled concrete and the measures to enhance its frost resistance. Furthermore, it aims to assist engineering and technical personnel in selecting appropriate treatment methods to improve the frost resistance of recycled concrete in cold regions, thereby promoting the practical engineering application of recycled concrete in such areas.

This paper analyses the impact of rubber additive content on the properties of cement composite. It describes the materials and the test methods used to determine various parameters of the composite mix and the cured composite. The properties of the cured composite were tested and compared. The effect of the amount of rubber additive on the following properties of cement composite was tested and analysed: slump flow, density, ultrasonic pulse velocity, compressive and flexural strengths, thermal conductivity, water absorption, and resistance to freeze-thaw cycles. The cement composite was produced by using crushed waste tyre granules as fine aggregate, i.e. sand was replaced with crushed tyre granules from 0 % to 10 %. The tests showed that the rubber additive used as sand replacement had little impact on the properties of the cement composite: density, ultrasonic pulse velocity, flexural and compressive strengths of the modified composite decreased, but resistance to freeze-thaw cycles increased. According to the test results and their analysis, 10 % is the optimal rubber additive content to be used as sand replacement in cement composite, which would have higher frost resistance and a lower coefficient of thermal conductivity.

Fruit crops are an irreplaceable source of essential nutrients, macro- and microelements, vitamins, organic acids, and antioxidants. Today, the overwhelming part of fruit supply in the market is provided by foreign producers. Import substitution and meeting the demand of the Russian Federation population for fruit consumption by the domestic agro-industrial complex is impossible without expanding the geography of cultivation areas, including those in zones of risky agriculture, which requires breeding of frost-resistant (cold-resistant) cultivars (fruit crops). Application of modern biotechnological and molecular genetic methods in breeding work will increase the profitability of fruit growing by reducing the time required for obtaining plants with the desired traits and by complex evaluation of the prospects of genotypes of parental forms. The present review considers modern data on cold tolerance genes of various fruit and berry crops, summarizes the known mechanisms of their action, activation, and regulation.The review considers modern data on genes of fruit and berry crops resistance to low temperatures, including characterization of genes encoding key receptors, signaling, effector proteins, and transcription factors in apple, pear, peach, pineapple, and strawberry. The known mechanisms of their operation, activation, regulation are given, and signaling cascades are described.

Abstract This study aims to research on the mechanical and frost resistance properties of pressed concrete blocks mixed with the polymeric aluminum chloride (PAC) waste residue. Experimental studies on the activity index of volcanic ash, mechanical property, frost resistance and microstructure of pressed concrete blocks mixed with PAC waste residue were carried out. The results show that the activity index of volcanic ash of PAC waste residue reaches 74.96% at a particle size of 0.075 mm or less and a curing age of 28 days. Based on results of mechanical property tests, the optimum dosage of PAC waste residue is 15%, at which time the compressive and bending strength only decreases by 14.57% and 15.84%. Based on results of frost resistance tests, the optimum dosage of PAC waste residue for pressed concrete blocks is 10%. After 50 freeze–thaw cycles, when the dosage of PAC waste residue is 10%, the strength loss rate is only 3.04%. XRD and SEM tests show that PAC waste residue participates in chemical reactions. With a small amount of PAC waste residue, the structure of the specimen remains dense and therefore the strength decreases less.

Low temperatures are one of the major abiotic stresses that affect alfalfa's development and yield. Enhancing frost resistance through resistance-related genes is one of the most effective ways to address this issue in alfalfa. Therefore, exploring cold-resistant gene resources and the cultivation of cold-resistant alfalfa cultivars is inevitable in order to achieve high yield and quality. In this study, we conducted transcriptome profiling of roots obtained from two alfalfa genotypes, i.e., Qingda No.1 for freeze tolerance and Gannong No.9 for freeze sensitivity. We observed that Qingda No.1 had more lateral roots and a more developed root system after overwintering, while Gannong No.9 had fewer lateral roots and an underdeveloped root system. After overwintering, Qingda No.1 exhibited higher superoxide dismutase (SOD) activity compared to Gannong No.9, while Gannong No.9 showed higher perosuperoxide dismutasexidase (POD) activity than Qingda No.1. We identified 25,935 differentially expressed genes, with 12 979 and 12 956 differential genes found in the freeze-tolerant variety Qingda No.1 group and the freeze-sensitive Gannong No.9 group, respectively. The enrichment of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways also differed between the two groups. We also discovered several gene family members, and the most frequent transcription factors were bHLH, B3, NAC, WRKY, and MYB_related. These findings provide comprehensive information to further understand the molecular mechanisms of adaptation to freezing stress in alfalfa and offer potential functional candidate genes for adaptation to abiotic stress.

Introduction. Large-scale field studies of the destruction of brickwork carried out by the author in many regions of the world showed that the approach to the research of the durability of building ceramics based on the strength parameter and the frost resistance parameter are not indicative. These parameters do not make it possible to obtain a temporary value of the durability of the material, but are just the basis for an expert assessment.Materials and methods. This paper proves the scientific hypothesis put forward by the author that the destruction of brick material in the brickwork of enclosing structures occurs under the influence of chemical corrosion processes. The process of chemical corrosion is described, the results of thermodynamic calculations of chemical processes are briefly presented. A brief description of the methods of studying the durability of the building ceramics material, which have now received the status of standards, is given.Results. The results of laboratory studies of the process of chemical destruction of the building ceramics material, as well as calculations of the durability of the building ceramics material performed on the basis of the developed method of calculating the durability of the material are presented.Conclusions. Based on the developed theoretical justification and laboratory studies of the process of chemical destruction of the wall ceramics material, it is concluded that the created research methodology and calculation method allow to determine the durability of the material at any stage of its operation.

This study aims to research on the mechanical and frost resistance properties of pressed concrete blocks mixed with the polymeric aluminum chloride (PAC) waste residue. Experimental studies on the activity index of volcanic ash, mechanical property, frost resistance and microstructure of pressed concrete blocks mixed with PAC waste residue were carried out. The results show that the activity index of volcanic ash of PAC waste residue reaches 74.96% at a particle size of 0.075 mm or less and a curing age of 28 days. Based on results of mechanical property tests, the optimum dosage of PAC waste residue is 15%, at which time the compressive and bending strength only decreases by 14.57% and 15.84%. Based on results of frost resistance tests, the optimum dosage of PAC waste residue for pressed concrete blocks is 10%. After 50 freeze–thaw cycles, when the dosage of PAC waste residue is 10%, the strength loss rate is only 3.04%. XRD and SEM tests show that PAC waste residue participates in chemical reactions. With a small amount of PAC waste residue, the structure of the specimen remains dense and therefore the strength decreases less. [ABSTRACT FROM AUTHOR]

To improve the in situ soil stabilization, different chemical additives are used (ion exchange compounds, additives based on H2SO4 or vinyl polymers, and organic additives using lignosulfonates). One interesting alternative is the production of additives from various waste materials. The extensive testing of waste-based blends with soil was performed; the mechanical (unconfined compressive strength (UCS)) and hydraulic (capillary rise, water absorption, and frost resistance (FR)) soil properties were measured. The optimization process led to obtaining additive compositions ensuring high strength and sealing properties: by-pass ash from the ceramics industry, waste H2SO4, pyrolytic waxes/oils from waste mixed plastics, waste tires and HDPE, and emulsion from chewing gum waste. For sandy soil, the following additives were the most promising: emulsion from pyrolytic wax (EPW) from waste PE foil (WPEF) with the addition of waste H2SO4, pyrolytic-oil emulsion from waste tires, EPW from waste mixed plastics with the addition of "by-pass" waste ash and NaOH, EPW from WPEF with the addition of NaOH, and EPW from WPEF reaching up to 93% FR, a 79.6% 7-day UCS increase, and a 27.6% of 28-day UCS increase. For clay: EPW from WPEF with the addition of NaOH, EPW from WPEF with the addition of waste H2SO4, and solely EPW from WPEF reaching up to 7.5% FR, an 80.7% 7-day UCS increase, and a 119.1% 28-day UCS increase. [ABSTRACT FROM AUTHOR]

The examinations of concrete involved partial substitution of cement with cement kiln dust (CKD) 0, 5, 10, 20 and 30%. The water/cement (w/c) ratio amounted to 0.36. The obtained findings pertaining to open porosity, density, and volumetric density were found to correlate with the capillary action and absorptivity of the analyzed types of concrete. With the maximum addition of CKD, i.e. 30%, open porosity decreased by 35%. In turn, CKD added in the amount of 5% resulted in a slightly reduced addition compressive strength, amounting to 1.3% and 2.1% following 28 days and 56 days of concrete curing, respectively. After 28 days, the differences in strength were greater when the additive was supplied in higher amounts, i.e. 10%, 20%, and 30%, resulting in 6.5%, 13.4%, and 22.9% decrease, respectively, in spite of strength improvement. In terms of flexural and splitting tensile strengths, comparable relations were noted. As far as the frost resistance test results are concerned, the mass losses in all examined concretes were not significant, reaching up to 0.5%. The strength reduction in the case of the first three series of concretes was below 3%. When the CKD addition was increased to 20% and 30%, the value of the dynamic modulus of elasticity Ec,s decreased to a greater degree, by 8.0% and 14.7%, respectively. The hydrophobization effect is best seen in CKD-free concrete. After the impregnation, the loss of mass following the frost test of the samples is reduced by half. With a higher CKD content, the hydrophobization effectiveness is insignificant. The most favourable results were observed for hydrophobization with the oligomer-based preparation A1. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In seasonally frozen regions, concrete pavement is exposed to cycles of freeze-thaw and erosion from de-icing salt, which can lead to unfavorable service conditions and vulnerability to damage. This paper examines the compressive strength, flexural-tensile strength, abrasion resistance, permeability, and spacing factor of concrete, taking into account the impact of various curing conditions, de-icing salt solutions, and mass fractions on the concrete's freeze-thaw resistance. Two test methods, the single-face method and the fast-freezing method, were used to comparatively analyze the freeze-thaw resistance of concrete. The analysis was based on the surface scaling, water absorption rate, mass loss rate, relative dynamic elastic modulus, and relative durability index. The results indicate that the presence of salt solution significantly worsened the degree of concrete damage caused by freeze-thaw cycles. The use of freeze-thaw media, specifically sodium chloride ( N a C l ), calcium chloride ( C a C l 2 ), and potassium acetate ( K A c ) at mass fractions of 5%, 4.74%, and 5%, respectively, had the greatest impact on the surface scaling of concrete. However, their effect on the water absorption rate was inconsistent. When the freeze-thaw medium was water, the concrete's relative dynamic elastic modulus and relative durability index were 9.6% and 75.3% higher, respectively, for concrete cured in 20 °C—95% RH conditions compared to those cured in 0 °C—50% RH conditions. We propose a comprehensive relative durability index ( D F w ) by combining the results of two methods of freeze-thaw tests. The D F w of concrete cured in 0 °C—50% RH conditions was 83.8% lower than that of concrete cured in 20 °C—95% RH conditions when exposed to a freeze-thaw medium of 5% mass fraction N a C l solution. To evaluate the salt freeze-thaw resistance of concrete pavement, it is recommended to use surface scaling and D F w together. [ABSTRACT FROM AUTHOR]

The global construction industry is increasingly utilizing concrete prepared from recycled aggregate as a substitute for natural aggregate. However, the subpar performance of recycled fine aggregate (RFA) has resulted in its underutilization, particularly in the structural concrete exposed to challenging environments, including those involving chlorine salts and freeze–thaw climates. This study aimed to enhance the performance of RFA as a substitute for river sand in concrete as well as fulfill the present demand for fine aggregates in the construction sector by utilizing accelerated carbonation treatment to create fully recycled aggregate concrete (FRAC) composed of 100% recycled coarse and fine aggregates. The impacts of incorporating carbonated recycled fine aggregate (C-RFA) at various replacement rates (0%, 25%, 50%, 75%, and 100%) on the mechanical and durability properties of FRAC were investigated. The results showed that the physical properties of C-RFA, including apparent density, water absorption, and crushing value, were enhanced compared to that of RFA. The compressive strength of C-RFC100 was 19.8% higher than that of C-RFC0, while the water absorption decreased by 14.6%. In a comparison of C-RFC0 and C-RFC100, the chloride permeability coefficients showed a 50% decrease, and the frost resistance increased by 27.6%. According to the findings, the mechanical and durability properties, the interfacial transition zones (ITZs), and micro-cracks of the C-RFC were considerably enhanced with an increased C-RFA content. [ABSTRACT FROM AUTHOR]

With the increasing severity of global climate change and environmental degradation, countries have put forward strategies to reduce carbon emissions and promote sustainable development. The construction industry is a major source of carbon emissions, and as such, the development of green concrete is now critically important to the industry's growth. Traditional concrete production methods use a lot of resources and produce a lot of carbon emissions. The study examines the use of recycled pumice and sodium dodecyl benzene sulfonate to modify waste rubber powder, which is then externally mixed into recycled coarse aggregate concrete. The study analyzes the impact of these modifiers on the rubber powder particles, as well as the effects of particle size and mixing amount on the resulting concrete. The investigation proved that the rubber recycled coarse aggregate concrete's performance was enhanced by the modifier. This improvement addressed the issue of low compressive strength in rubber concrete to some extent and also had a positive impact on its resistance to freeze-thaw cycles. The experiment concluded that the best results were achieved by selecting rubber powder particles of Sipan 40 with a mesh size of 80 mesh and an external admixture of 6%. This type of green concrete can solve the problem of construction waste disposal while also enhancing the performance and durability of the concrete. It has a promising future application prospect. [ABSTRACT FROM AUTHOR]

With the continuous advancement of urbanization construction, the number of discarded red bricks caused by construction demolition is impressive because of the characteristics of construction materials in the early stage of our country. This study used the recycled brick powder produced in crushing red waste bricks to partially or wholly replace quartz sand, combined with different doses of PVA fiber to prepare green recycled brick powder engineering cementitious composites (ECC). First, the strain hardening and multiple cracking behaviors of recycled brick powder ECC with different fitting ratios were verified using four-point bending tests. Then, a rapid freeze-thaw experiment was conducted to study the effects of different fitting ratios on the quality failure rate, phase dynamic elastic modulus, and compressive flexural resistance of recycled brick powder ECC. Based on the evaluation parameters of compressive strength loss rate and frost resistance, the ECC freeze-thaw prediction model of recycled brick powder was established by the Monte Carlo method to expand the number of samples. The research results show the best frost resistance of recycled brick powder ECC with a 25% recycled brick powder ratio and 1% PVA fiber. Scanning electron microscopy was used to observe raw materials and cement-based materials, and the reasons of macroscopic phenomena were explained from a microscopic perspective. [ABSTRACT FROM AUTHOR]

The effects of gold tailings and polyvinyl alcohol (PVA) fibre on the frost resistance of engineered cementitious composites (ECC) were investigated. The ECC were made with three gold tailings dosages and four PVA fibre contents. A water/binder (w/b) ratio of 0.28 was used for all mixtures. Surface damage, mass loss, relative dynamic elastic modulus, compressive strength and damaged layer thickness (DLT) were investigated to assess the frost resistance of the ECC. The results showed that the effect of gold tailings on the frost resistance of the ECC was marginal, but the frost resistance increased with an increase in PVA fibre content. The ECC with the addition of gold tailings had the same excellent frost resistance as those without gold tailings, indicating that it is feasible to replace silica sand with gold tailings at up to 100% replacement. A model to predict the DLT in ECC as a function of gold tailings dosage and freeze–thaw cycles was developed. [ABSTRACT FROM AUTHOR]

Concrete pumping technology is widely used in reservoirs, dams, harbours and other hydraulic structures. To investigate the effects of pumping on the flowability, mechanical strength and frost resistance of hydraulic concrete, long-distance pumping tests were carried out on self-compacting concrete (SCC). This paper investigated the influence of high-pressure pumping on the workability, mechanical strength and frost resistance of SCC by analysing the changes in various properties of SCC before and after long distance pumping. The flowability of the fresh concrete decreased after long-distance pumping. Compared to before pumping, the slump of the four groups of SCC decreased by an average of 3.93% and the slump-flow decreased by an average of 23.09%. The homogeneity and stability of the fresh SCC improved significantly after pumping. After pumping, the V-funnel time of SCC was reduced by an average of 82.32% and the segregation rate was reduced by an average of 125.76%. Additionally, there was a slight increase in mechanical strength indicated by an average increase of 5.87% in cubic compressive strength, 8.99% in axial compressive strength, 7.78% in tensile splitting strength, and 5.22% in modulus of elasticity. Notably, the frost resistance of the SCC showed significant improvement after pumping. Under non freeze–thaw conditions, the compressive strength of SCC after pumping increased by an average of 5.87%. After 200 freeze–thaw cycles, the compressive strength (after pumping) increased by an average of 12.46%. An air void analyser was then used to test the air-void parameters to analyse the effect of long-distance pumping action on the air voids parameters. The study further established the correlation between air-void structure characteristics and freeze–thaw resistance. Under freeze–thaw conditions, the compressive strength showed a linear correlation with air content and spacing factor. The process of pumping can enhance the air-void structure of SCC, leading to improved frost resistance. Therefore, in the design of concrete frost resistance, pumping can be considered as an influencing factor to improve the frost resistance of concrete. [ABSTRACT FROM AUTHOR]

Due to climate change and the recent increase in the number of floods in urbanized areas, there is a growing need for the introduction of new technologies into the road material market. One such technology is waterpermeable mineral-resin surfaces, which are becoming increasingly popular. However, due to a lack of clear requirements and solution approval procedures, they are not commonly used in public investments. This paper first describes the materials used for preparing surface samples, including bulk density and granulometric aggregate tests, consistency, colour, and density at 20 °C testing of the hardener and resin. It then outlines the process of sample preparation and provides a brief description of the materials used. The tests conducted on the prepared material samples included flexural and compressive strength tests, frost resistance tests under normal conditions and in the presence of salts, and skid resistance tests. Based on the results obtained, it can be generally concluded that, in the case of permeable surfaces, the type of aggregate is an important factor, as evidenced by the results of the strength tests. The same can be stated about the influence of atmospheric factors. Tests conducted with granite aggregate proved to be more resistant to cyclically changing temperatures, even in the presence of salt. [ABSTRACT FROM AUTHOR]

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Copyright of Fly Ash Comprehensive Utilization is the property of Hebei Fly Ash Comprehensive Utilization Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report the synthesis of poly(acrylamide-co-acrylic acid)/sodium carboxy methyl cellulose (PAMAA/CMC-Na) hydrogels, and subsequent fabrication of dual-network polymer hydrogels (PAMAA/CMC-Na/Fe) using as-prepared via the salt solution (FeCl3) immersion method. The created dual-network polymer hydrogels exhibit anti-swelling properties, frost resistance, high conductivity, and good mechanical performance. The hydrogel swells sightly when immersed in solution (pH = 2~11). With the increase in nAA:nAM, the modulus of elasticity experiences a rise from 1.1 to 1.6 MPa, while the toughness undergoes an increase from 0.18 to 0.24 MJ/m3. Furthermore, the presence of a high concentration of CMC-Na also contributes to the enhancement of mechanical strength in the resulting hydrogels, ascribing to enhanced physical network of the hydrogels. The minimum freezing point reaches −21.8 °C when the CMC-Na concentration is 2.5%, owing to the dissipated hydrogen bonds by the coordination of Fe3+ with carboxyl (-COO−) in CMC-Na and PAMAA. It is found that the conductivity of the PAMAA/CMC-Na/Fe hydrogels gradually decreased from 2.62 to 0.6 S/m as the concentration of CMC-Na rises. The obtained results indicates that the dual-network hydrogels with high mechanical properties, anti-swelling properties, frost resistance, and electrical conductivity can be a competitive substance used in the production of bendable sensors and biosensors. [ABSTRACT FROM AUTHOR]

Featured Application: The study of the freeze–thaw cycling and impact resistance properties of rubberized concrete materials can provide a better understanding and mastery of the durability performance of rubberized concrete materials. It holds significant theoretical and practical value for actual engineering projects in cold regions. To improve the long-term performance of concrete engineering in high-altitude areas, waste tire rubber was added to a concrete mix, and freeze–thaw and impact tests were conducted. The effects of waste tire rubber with different particle sizes (10, 20, 30 mesh) and freeze–thaw cycles (0, 25, 50, 75, 100, 125) on the dynamic mechanical properties of concrete materials were studied. The stress–strain curves, peak stress, and fracture morphology of the specimens were analyzed. The microstructure changes of the specimens were also analyzed using scanning electron microscopy (SEM). The results showed the following: (1) Both macroscopic and microscopic analysis results showed that the internal damage of rubber concrete specimens was smaller after freeze–thawing, and the integrity was better after impact, maintaining a loose but not scattered state. The addition of waste tire rubber significantly improved the material's impact resistance to a certain extent. (2) As the impact pressure increased, the strain rate of the specimens increased linearly, and the dynamic peak stress was linearly positively correlated with the strain rate. (3) After 125 freeze–thaw cycles, the peak stress of the specimens with 30-mesh added rubber decreased significantly less than that of ordinary concrete under 0.3, 0.45, and 0.6 MPa impact pressure. The dynamic peak stress was higher than that of specimens with 10-mesh and 20-mesh added rubber, and the addition of 30-mesh rubber significantly improved the frost resistance and impact resistance of concrete materials. This study can provide new ideas for the engineering application of rubber concrete. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to protect the natural resources, it is beneficial for the environment when materials that are not valuable, such as waste or recycled materials, are used in engineering. This article presents laboratory studies on the use of mixtures of incineration bottom ash (IBA) from municipal waste incinerators with natural, fine grain and uniform aggregate in cement-bound layers. The mechanical and engineering properties of aggregates were studied, their usefulness was assessed and possible applications are indicated. The chemical composition of the material was found to be consistent with typical IBA from other incineration plants, and leachability studies were carried out, confirming lack of any environmental impact. The authors' own mixtures were prepared based on optimal water content and maximal dry densities of solid particles, and the compressive strength was calculated after 7 and 28 days of hardening. The results indicate that replacing natural aggregates with IBA permits an increase in the compressive values for the specimens using the same amount of CEM I 42.5R while improving the frost resistance of cement–aggregate mixtures. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles, the freeze-thaw damage degree of the hybrid fiber reinforced concrete with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.

This study aims to investigate the influence of different fiber types, lengths, and contents on their performance in freeze-thaw environments. Indoor freeze-thaw tests were conducted to evaluate the flexural strength, compressive strength, and mass loss of fiber-reinforced geopolymer materials. Additionally, SEM and XRD analyses were performed to examine the internal structure of the geopolymer composites. The results demonstrated that the incorporation of different fibers significantly improved various properties, particularly the flexural strength of the specimens. With an increasing number of freeze-thaw cycles, surface cracks became more prominent in the geopolymer specimens, leading to a gradual decrease in frost resistance. However, the addition of an appropriate amount of fiber effectively enhanced frost resistance. Following freeze-thaw exposure, an increase in fiber content initially resulted in a decrease and subsequently an increase in relative flexural strength, compressive strength, and mass loss. Notably, studies revealed that polypropylene fibers with a length of 9 mm and a content of 0.9 % exhibited minimal mass and strength loss. SEM analysis indicated uniform distribution of fibers within the geopolymer matrix, contributing to improved flexural strength and enhanced frost resistance in fiber-reinforced structures. XRD results indicate that red mud-slag based geopolymers produce high-strength hydrated calcium (aluminosilicate) silicate and hematite phases, which enhances the mechanical properties and durability of the specimens. In conclusion, this study highlights that incorporating suitable fibers can enhance the durability and performance of red mud-slag based geopolymers under freeze-thaw conditions. The findings provide valuable insights for optimizing fiber type, length, and content to achieve superior mechanical properties and frost resistance in geopolymer composites.