Frost Resistance Research Articles

Complex additive for improving the strength properties of heavy concrete based on industrial waste

The article presents the results of using a complex modified additive to improve concrete's physical and mechanical properties. The complex additive includes industrial production wastes: metallurgical slag and alcohol production wastes (post-alcohol bard). To stabilize the hydrogen index the alkali KON is included in the composition of the additive. A set of laboratory studies was carried out to measure the strength, absorption, and frost resistance of test specimens to assess the effect of the additive on the properties of concrete. A comparison of physical and mechanical properties was made for samples of different concentrations of slag. The ratio of slag components to cement was from 5 to 25% by the total mass of the binder, a multiple of 5%. The optimal composition of the mixture, with maximum strength values, corresponds to the percentage of slag 15%, post-alcohol bard 22.5 liters, and alkali 150 grams. In general, the results obtained from data points of the compared parameters showed consistent results with minimal variation in the data. The results obtained are of practical value related to the reduction of the cost of production of structural concrete with an increase in its strength indicators.

Frost resistance and improvement techniques of recycled concrete: a comprehensive review

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.

Application of recycled concrete aggregates in continuous-graded cement stabilized macadam

This study investigates the potential of using recycled concrete aggregate (RCA) derived from construction and demolition waste as a replacement for natural aggregate in cement-stabilized macadam (CSM). Various substitution rates of RCA, ranging from 0 % to 100 %, were examined with a focus on mechanical properties and durability, including unconfined compressive strength (UCS), indirect tensile strength (ITS), compressive elastic modulus, drying shrinkage, frost resistance, scour resistance, and water damage resistance. Nanoindentation was used to analyze the interfacial transition zones (ITZs) within the CSM. The results show that with a fixed cement content, the UCS, ITS, and compressive elastic modulus decrease as the RCA content increases. Higher RCA content also leads to reduced drying shrinkage, frost resistance, scour resistance, and water damage resistance. Nanoindentation revealed that ITZ1 and ITZ2 have similar thicknesses (∼50 μm), while ITZ3 is about 80 μm thick, highlighting the intricate physical composition of ITZs, including pores, low-density C-S-H, high-density C-S-H, and Ca(OH)2. These findings provide critical insights for optimizing sustainable CSM design using RCA, thereby promoting environmental sustainability in road construction.

The screening effect of coarse aggregate on the air void structure and durability of air-entrained concrete

The control of air void structures introduced by air-entraining agents (AEAs) has long been a crucial problem. However, the mechanism through which the air void structure is refined by the extrusion of the slurry and the cutting of the aggregate remains insufficiently studied. This study aims to investigate the screening effect of coarse aggregate on the air void structure. The gradations of coarse aggregates were controlled by the fractal dimension (D). For casting air-entrained concrete, multiple continuously graded aggregates with D of 2.1, 2.3, 2.5 and 2.7 as well as two single graded aggregates with D=1.8 and 3.0 were used. Various parameters such as air content, air void structure, freeze-thaw durability, chloride ion permeability and water absorption were measured. Various air void structure parameters were compared to macroscopic properties. To evaluate the screening effect of coarse aggregate, the bubble rising and splitting behavior when passing through a single simulated aggregate (SA) and SA layer were observed. The findings indicate that finer and continuously graded coarse aggregates lead to higher air content and promoted air bubble trapped rate, which suggests a stronger screening effect. This results in a smaller bubble spacing coefficient and stronger frost resistance.

The Basic Properties of Lightweight Artificial Aggregates Made with Recycled Concrete Fines

The production of lightweight aggregate based on waste is an important step towards sustainable and ecological construction. It contributes to reducing the negative impact of the construction sector on the environment by reducing the consumption of natural raw materials and reducing waste of various origins, including rubble concrete. The physical and mechanical properties, including grain shape index, water absorption, bulk density, resistance to crushing, frost resistance, leachability of heavy metals, and porosity of lightweight artificial aggregate made from rubble concrete waste (KRC) were presented in the paper. The obtained test results prove that the proposed artificial aggregate has similar water absorption and bulk density and even better frost and crushing resistance than artificial aggregates available on the market. Due to its properties, it can be used for lightweight concrete, gardening, or as a separating layer in home sewage treatment plants.

Monitoring weekly δ 13С variations along the cambium-xylem continuum in the Canadian eastern boreal forest.

Intra-annual variations of carbon stable isotope ratios (δ13C) in different tree compartments could represent valuable indicators of plant carbon source-sink dynamics, at weekly time scale. Despite this significance, the absence of a methodological framework for tracking δ13C values in tree rings persists due to the complexity of tree ring development. To fulfill this knowledge gap, we developed a method to monitor weekly variability of δ13C in the cambium-xylem continuum of black spruce species [Picea mariana (Mill.) BSP.] during the growing season. We collected and isolated the weekly incremental growth of the cambial region and the developing tree ring from five mature spruce trees over three consecutive growing seasons (2019-2021) in Simoncouche and two growing seasons (2020-2021) in Bernatchez, both located in the boreal forest of Quebec, Canada. Our method allowed for the creation of intra-annual δ13C series for both the growing cambium (δ13Ccam) and developing xylem cellulose (δ13Cxc) in these two sites. Strong positive correlations were observed between δ13Ccam and δ13Cxc series in almost all study years. These findings suggest that a constant supply of fresh assimilates to the cambium-xylem continuum may be the dominant process feeding secondary growth in the two study sites. On the other hand, rates of carbon isotopic fractionation appeared to be poorly affected by climate variability, at an inter- weekly time scale. Hence, increasing δ13Ccam and δ13Cxc trends highlighted here possibly indicate shifts in carbon allocation strategies, likely fostering frost resistance and reducing water uptake in the late growth season. Additionally, these trends may be related to the black spruce trees' responses to the seasonal decrease in photosynthetically active radiation. Our findings provide new insights into the seasonal carbon dynamics and growth constraints of black spruce in boreal forest ecosystems, offering a novel methodological approach for studying carbon allocation at fine temporal scales.

Ultra-Stretchable, Adhesive, Conductive, and Antifreezing Multinetwork Borate Ester-Based Hydrogel for Wearable Strain Sensor and VOC Absorption.

Hydrogels based on borate ester bonds exhibit remarkable tensile strength and self-healing ability, which make them a promising material for various biological research and strain sensor applications. However, in order to meet the practical application of hydrogel strain sensors, they must also show high conductivity, frost resistance, and proper adhesion, which is still a continuous challenge. Herein, a triple network hydrogel was prepared using poly(vinyl alcohol) (PVA) as the first network, ethylene imine polymer (PEI) as the second network, and poly(acrylamide-co-acrylic acid) copolymer (denoted as P(AM-Co-AA)) as the third network. 3-Carboxy-4-fluorophenylboronic acid (CFBS) was used as the cross-linking agent, glycerol (GL) was added to improve low-temperature resistance, and sodium chloride (NaCl) was incorporated to enhance electrical conductivity. The resulting PVA-CFBS@PEI@P(AM-Co-AA) triple network hydrogel exhibited impressive mechanical properties, including ultra tensile strength (4100%, 266.8 kPa), high toughness (6.5 MJ/m3), and low-temperature resistance (-60 °C). Additionally, it demonstrated high conductivity (σ = 1.83 mS/cm). The incorporation of CFBS endowed the hydrogel with excellent self-healing ability, while GL improved low-temperature resistance and strain sensing sensitivity (gauge factor (GF) = 2.8 (0-300%), GF = 5.6 (300-600%), GF = 8.7 (600-1000%)). The prepared hydrogel sensor can repetitively detect and differentiate between a wide range of human activities such as joint movements, frowning, and smiling. Additionally, the hydrogel demonstrated favorable mechanical properties at -20 °C (good adhesion, tensile strength: 1169.8%, 1.2 MPa; conductivity: 0.71 mS/cm, and strain sensing coefficient: GF = 1.3), making it suitable for applications in low-temperature environments. Furthermore, it also functions as an exceptional adsorbent, capable of selectively absorbing volatile organic compounds at high capacity (e.g., methanol: 1.80 g/g; acetone: 1.50 g/g).

Study on the Performance of High-Performance Mortar (HPM) Prepared Using Sodium-Silicate-Modified Graphite Tailing Sand

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.

Mechanical Properties of Recycled Concrete Incorporated with Super-Absorbent Polymer and Machine-Made Stone Powder under the Freeze-Thaw Cycle Environment.

Recycled concrete incorporating additional super-absorbent polymer (SAP) and machine-made stone powder (MSP) was prepared using a two-factor, four-level orthogonal test. To enhance the frost resistance of recycled concrete and improve its mechanical properties, such as compressive and flexural strength, the prepared concrete underwent 200 freeze-thaw cycles. Before freeze-thaw cycles, the amount of SAP has a predominant influence on the mechanical properties of recycled concrete in comparison with MSP. After 200 cycles of freeze-thaw, the influence of MSP became more significant than that of SAP. Typically, the compressive strength and flexural strength exhibited a trend of initially increasing and then decreasing as the contents of SAP and MSP increased. The optimized recycled concrete was identified as S16M6, containing 0.16% SAP and 6% MSP, as demonstrated by the minimal strength loss after freeze-thaw cycles. This study also proposed a linear regression model for predicting the mechanical properties which offered valuable guidance for the engineering application of recycled concrete mixed with SAP under the freeze-thaw cycle environment.

Experimental Study on the Strength and Durability of Manufactured Sand HPC in the Dalian Bay Undersea Immersed Tube Tunnel and Its Engineering Application

The usage of manufactured sand concrete is widespread in modern engineering, and it is important to study its performance to improve the overall engineering quality. This paper presents an experimental study on the working performance and durability of 12 groups of manufactured sand high-performance concrete (MSHPC) with varying mix ratios, in the context of the construction of the Dalian Bay undersea immersed tube tunnel. The study reveals that the stone powder content significantly affects the physical and mechanical properties, as well as the durability, of manufactured sand concrete. At an approximately 9% stone powder content, the concrete achieves the highest slump and best workability. However, excessive stone powder reduces early crack resistance. Furthermore, an optimal stone powder content (ranging from 5% to 13%) enhances the compressive strength, with the 28-day compressive strength reaching 60 MPa at a 13% stone powder content, while the effect on the splitting tensile strength is negligible. The stone powder content does not significantly impact impermeability and frost resistance, but at 7–9%, the RCM method shows the lowest chloride ion diffusion coefficient. Additionally, a lower water–binder ratio enhances resistance to chloride ion diffusion. High-performance RCM concrete with a 9% stone powder content was used in the construction of the Dalian Bay Cross-Harbor Tunnel, achieving 28-day and 56-day compressive strengths of C45 and C50, respectively, an impermeability grade of P14, a chloride ion diffusion coefficient of 1.9 × 10−12 m2/s, and a frost durability index of 92%, meeting the project’s 100-year lifespan design requirements.

Economic and biological assessment of a new medium-ripened variety of soft winter wheat Priazovye

Relevance. In the Russian Federation, winter common wheat is the main food and strategic crop. Permanent improvement of productivity and quality of wheat grain, reducing its production costs is the main task of agricultural production. To solve this problem, the leading place is given to the continuous and constant creation and introduction into production of new competitive wheat varieties, highly adapted to stress factors, with guaranteed high yields and high grain quality.Methods. The research was carried out in the southern zone of the Rostov region at the experimental sites of the Federal State Budgetary Scientific Institution ANTS “Donskoy” in 2021–2023 in order to create a new variety of soft winter wheat capable of forming not only high yields, but also having high frost resistance, drought resistance, resistance to leaf diseases, possessing high rheological and technological properties of grain and flour.Results. The winter common wheat variety Priazovie was developed by stepwise hybridization using the varieties Voyazh and Tanya. This is a highly productive variety. On average, over three years (2021–2023) of study in the competitive variety testing, the productivity of the variety laid in green manure fallow was 9.88 t/ha, exceeding that of the standard variety by 1.56 t/ha. The variety is capable of producing high yields after various forecrops. The maximum productivity of the variety (12.23 t/ha) was obtained in green manure fallow in 2022. The variety forms a high stem capacity (up to 800 pcs/m²), and is characterized by high resistance to the main leaf diseases, such as powdery mildew, brown and yellow mildew, loose smut, leaf blotch, etc. According to the main indicators of grain and flour quality, it belongs to valuable wheat, in terms of frost resistance (73.3%) it surpasses the standard Ermak variety (69.2%).

The Influence and Mechanism of Polyvinyl Alcohol Fiber on the Mechanical Properties and Durability of High-Performance Shotcrete

This study investigates the impact of polyvinyl alcohol (PVA) fibers on the mechanical properties and durability of high-performance shotcrete (HPS). Results demonstrate that PVA fibers have a dual impact on the performance of HPS. Positively, PVA fibers enhance the tensile strength and toughness of shotcrete due to their intrinsic high tensile strength and fiber-bridging effect, which significantly improves the material’s splitting tensile strength, deformation resistance, and toughness, and the splitting tensile strength and peak strain have been found to be increased by up to 30.77% and 31.51%, respectively. On the other hand, the random distribution and potential agglomeration of PVA fibers within the HPS matrix can lead to increased air-void formations. This phenomenon raises the volume content of large bubbles and increases the average bubble area and diameter, thereby elevating the pore volume fraction within the 500–1200 μm and >1200 μm ranges. Therefore, these microstructural changes reduce the compactness of the HPS matrix, resulting in a decrease in compressive strength and elastic modulus. The compressive strength exhibited a reduction ranging from 10.44% to 15.11%, while the elastic modulus showed a decrease of between 8.09% and 12.67%. Overall, the PVA-HPS mixtures with different mix proportions demonstrated excellent frost resistance, chloride ion penetration resistance, and carbonation resistance. The electrical charge passed ranged from 133 to 370 C, and the carbonation depth varied between 2.04 and 6.12 mm. Although the incorporation of PVA fibers reduced the permeability and carbonation resistance of shotcrete, it significantly mitigated the loss of tensile strength during freeze–thaw cycles. The findings offer insights into optimizing the use of PVA fibers in HPS applications, balancing enhancements in tensile properties with potential impacts on compressive performance.

Evaluation on Preparation and Performance of a Low-Carbon Alkali-Activated Recycled Concrete under Different Cementitious Material Systems.

A green, low-carbon concrete is a top way to recycle waste in construction. This study uses industrial solid waste slag powder (S95) and fly ash (FA) as binders to completely replace cement. This study used recycled coarse aggregate (RCA) instead of natural coarse aggregate (NCA). This is to prepare alkali-activated recycled concrete (AARC) with different cementitious material systems. Alkali-activated concrete (AAC) mixtures are modified for strength and performance based on the mechanical qualities and durability of AARC. Also, the time-varying effects of the environment on AARC properties are explored. The results show that with the performance enhancement of RCA, the mechanical performance of AARC is significantly improved. As RCA's quality improves, so does AARC's compressive strength. At a cementitious material content of 550 kg/m3, AARC's 28d compressive strengths using I-, II-, and III-class RCA were reduced by 2.2%, 12.7%, and 21.8%, respectively. I-class AARC has characteristics similar to natural aggregate concrete (NAC) in terms of shrinkage, resistance to chloride penetration, carbonization, and frost resistance. AARC is a new type of green building material that uses industrial solid waste to prepare alkali-activated cementitious materials. It can effectively reduce the amount of cement and alleviate energy consumption. This is conducive to the reuse of resources, environmental protection, and sustainable development.

Fire Safety and Impact and Frost Resistance of Basalt Fiber-Reinforced Polysiloxane Matrix Composite Processed under Partial Pyrolysis Conditions

Fire Safety and Impact and Frost Resistance of Basalt Fiber-Reinforced Polysiloxane Matrix Composite Processed under Partial Pyrolysis Conditions

Experimental investigation on the frost resistance of RCC layers with various interface treatments

This research investigates the influence of various interface treatment methods on the frost resistance performance of Roller Compacted Concrete (RCC) layers. Freeze-thaw cycle tests were conducted on RCC with interfaces treated using cement mortar, expansion agent mortar, and nano-SiO2 mortar. The study evaluated shear failure modes, shear strength, crack expansion, pore structure, and liquid uptake of the RCC interface after freeze-thaw cycles under different treatment methods. Results reveal that expansion agent mortar and nano-SiO2 mortar improve the shear strength of RCC after freeze-thaw cycles more effectively than cement mortar. The freeze-thaw cycles increase the width and expansion rate of cracks at the RCC interface during the shear process, while mortar treatments help delay crack development. Additionally, the pore volume at the RCC interface gradually increases, and the uniformity of pore distribution decreases under freeze-thaw cycles. During liquid uptake, mortar treatments slow down the upward migration of liquids by improving the pore structure at the interface. The liquid uptake of RCC exhibits a distinct linear relationship with its shear strength and pore structure. As liquid uptake time increases, water first fills larger pores before gradually entering smaller ones. Freeze-thaw cycles cause an increase in pore volume and enlargement, which leads to greater liquid uptake. Based on the damage mechanism of the RCC interface under freeze-thaw conditions, a model of shear strength degradation due to freeze-thaw cycles was established, aligning well with experimental results. Mechanism analysis indicates that nano-SiO2 and expansion agents enhance frost resistance by filling interface pores and cracks through reactions with certain compounds, thereby improving the microstructure.

TECHNOLOGY FOR THE PRODUCTION OF COMPOSITE MATERIAL-SULFUR CONCRETE PRODUCTS FROM MODIFIED SULFUR

Due to the increase in the processing of sulfur-containing hydrocarbon raw materials (oil and gas), sulfur is released as one of the large - tonnage waste. Long-term storage of large sulfur reserves has a negative impact on the environment. Composite material of sulfur modification-characterized by environmental efficiency, economic efficiency in construction. This review examines the sources of sulfur origin, properties, technology for making sulfur concrete from it and the use of sulfur-based concrete in the construction industry today. Experimental evaluation of modified sulfur concrete, other methods of preparation of mixtures were identified, and the importance of adaptation to foreign experience in the development of sulfur concrete production was shown. One of the most promising projects is the production of concrete containing sulfur binder in order to reduce the load on the environment. After all, sulfur concrete has such advantages as resistance to acid and radiation, frost resistance and the ability to recycle. The aim of the work was to study a new composition of sulfur concrete based on a bitumen composition. To conduct the study, samples of sulfur concrete with different percentage contents of the constituent components were prepared.

Sustainable stabilization/solidification of Cu-contaminated seasonal frozen soil by epoxy resin: environmental risk assessment and engineering applicability

There are significantly toxic Cu contaminants in seasonal frozen soil areas under industrial production and mineral exploitation. However, the hydration reactions of mainstream alkaline curing agents such as cement are disturbed by the solidification and thawing of moisture, and their solidification/stabilization is ineffective to heavy metals. Therefore, there is an urgent requirement to optimize the use of current curing agents to improve the solidification/stabilization (S/S) effect of Cu contaminants in seasonal frozen soil areas. In this study, the Epoxy resin (EP) with excellent waterproofing and frost resistance was incorporated into artificially prepared Cu-contaminated soil to maintain a steady engineering application strength and inhibit the outward diffusion of toxic Cu contaminants under freeze-thaw cycles. The freeze-thaw resistance of EP-cured Cu-contaminated soil and the feasibility of EP remediation technology have been investigated, including mechanical properties, environmental effects and microstructure. The decline in mechanical strength and the increment in Cu leaching during freeze-thaw cycles are effectively suppressed by the remediation of EP. Even after 8 freeze-thaw cycles, there is merely a mechanical strength decline of 5%, solely a secondary Cu leaching of 4.74mg/L, and astonishingly a leachable index of 11.70 in the specimens with 12% EP dosage. The expansion phenomenon of pores and clay fractures under freeze-thaw cycles were gradually alleviated after incorporation of EP. The above results demonstrate the Cu-contaminated seasonal frozen soil remedied by EP are high-strength, basically non-toxic, and environmentally friendly material which are suitable for in-situ stabilization/solidification in seasonal frozen soil areas.

Modification of the polymeric admixture based on polycarboxylate ether using silica-derived secondary materials obtained from fly ash and the efficiency of its application in concrete

The rising energy prices and the costs of CO2 emissions into the atmosphere are forcing the construction industry to search for ways to reduce cement consumption in concrete technology by optimizing concrete mixtures and making greater use of chemical admixtures. The scientific problem lies in understanding how polymers modified with silica-derived secondary materials, such as those obtained from fly ash (e.g., synthetic zeolites, mesoporous silica), interact with the concrete matrix and influence their durability and strength. The present study investigated the effect of a polymeric admixture based on polycarboxylic ether (PCE) modified with silica-derived secondary materials obtained from fly ash (synthetic zeolites, mesoporous silica) on the physical and mechanical properties of concrete. The study considered the effect of the modified polymer admixture dosed in 3 different amounts (0.4%, 0.8% and 1.2%) by weight of cement on the fresh properties of the concrete mixture, i.e. consistency and air content. The research scope also included determining the physico-mechanical properties of the concretes and investigating the effect of the modified admixture on the frost durability of the cement composite. In order to study the modification of the concrete microstructure, XRD phase analysis and air pore structure analysis by MIP were carried out. The study showed an increase in compressive strength after 28 days of curing in concretes containing the modified polymer of about 8-12% compared to the reference concrete. In addition, it was observed that strength increased with increasing admixture dosage. The resulting pore structure, contributed to improving the frost resistance of the concretes by reducing compressive strength loss from about 14% in reference concretes to about 2-9% in concretes with the modified polymer after 150 cycles of alternating freeze-thaw. At the same time, it was observed that the use of the modified polymer resulted in an increase in weight absorption from 2% do 4.5%, a more than twofold increase in depth of penetration of water under pressure and a more than 70% increased total porosity. In conclusion, the polymer-modified MCM-41 can positively affect the mechanical and durability properties of concrete, but it causes a change in the pore structure, which could have a negative effect on water absorption and total porosity.

PSO-BP model for assessing frost resistance in containment concrete with varying pipe diameters

The safety of containment concrete is of utmost importance for nuclear power plants. The presence of pipe openings in the containment concrete structure introduces weakened areas, which adversely impact the mechanical properties and durability of the concrete. However, little research has been done on the durability of containment concrete with embedded steel pipe (CCESP), and no studies are found on its frost resistance under single-side freezing and thawing conditions. In this paper, using single-side salt freeze-thaw experiment to simulate the practical situation of coastal containment concrete, the effect of different steel pipe diameters (d) on the frost resistance of containment concrete was investigated. Based on the experimental results and using backpropagation neural networks optimized by a particle swarm algorithm (PSO-BP), a model was established to predict the frost resistance of CCESP for varying values of d. The research results showed that wall effects and stress concentrations created an interface zone between the steel pipes and the concrete, leading to a decline of compressive strength. Freeze-thaw cycles had only a slight impact on the relative dynamic elastic modulus (E) of CCESP, while the exfoliation mass per unit area (M) of the concrete specimens increased linearly with d. It indicates that pipe opening adversely impacts the frost resistance of the concrete, and that M can be used to evaluate the frost resistance of CCESP. This study addresses the research gap in the frost resistance of containment concrete with steel pipe openings, and the proposed PSO-BP model can accurately predict the frost resistance of containment concrete with varying pipe diameters under different freeze-thaw cycles.

Salt-freeze resistance and life prediction of geopolymer recycled concrete mixed with rice husk ash and modified rubber particles

Rice husk ash (RHA) and Span-40 modified waste rubber particles (WRP) were mixed into geopolymer recycled concrete (GRC) to improve its frost resistance in normal and chlorine environment. The freeze-thaw and static loading test results show that GRC has the best freeze-resistance when 5 %RHA and 10 %WRP are added. The strength loss rate of GRC after 200 freeze-thaw cycles in normal environment and chlorine salt environment is 8.3 % and 8.8 % lower than that of GRC without RHA and modified WRP, respectively. Based on the test results, the material damage model and strength loss model of GRC doped with RHA and modified WRP were established. The failure probability and service life of GRC were predicted. The results showed that the failure probability of GRC mixed with 5 %RHA and 10 %WRP was reduced by more than 10 % compared with that of GRC mixed with no RHA and modified WRP at 200 freeze-thaw cycles under normal environment and chlorine salt environment, and the failure probability decreased with the increase of cycle times. The life prediction results showed that the service life of GRC mixed with 5 %RHA and 10 %WRP increased by 17.9 % and 21.6 %, respectively, compared with that of GRC mixed with no RHA and modified WRP under the freeze-thaw cycle of normal environment and chlorine salt environment.