Ordinary Concrete Research Articles

Mechanical Properties and Chloride Salt Corrosion Resistance of All-Lightweight Shale Ceramsite Concrete

In investigating the mechanical properties and chloride corrosion resistance of all-light shale ceramsite concrete (ALSCC), samples of ALSCC20–ALSCC45 with a compressive strength of C20–C45 were individually prepared. The compressive strength, split tensile strength, and elastic modulus of ALSCC were analyzed. Additionally, the chloride salt corrosion resistance of ALSCC was assessed by examining chloride ion penetration depth, steel corrosion rate, and compressive strength after ALSCC30 corrosion. Furthermore, the microstructure of ALSCC hydration products was observed using scanning electron microscopy (SEM). Results indicate that as the strength grade increases, the water–cement ratio decreases, and the internal structure becomes denser, thereby improving the mechanical and corrosion resistance properties of ALSCC. Notably, the chloride corrosion resistance of ALSCC surpasses that of ordinary concrete. SEM images reveal that the hydration of ceramsite with Ca(OH)2 in concrete generates Ca[Al(OH)4]2 precipitation and C–S–H gel, which enhances internal filling and improves chloride corrosion resistance. Furthermore, based on the results of the ALSCC30 corrosion test, a calculation model for predicting compressive strength in a chloride environment was proposed. This model effectively predicts the compressive strength of ALSCC under chloride exposure conditions.

Economic and Environmental Benefit Analysis between Crumb Rubber Concrete and Ordinary Portland Cement Concrete

Although manifold empirical studies have identified the mechanical properties of crumb rubber concrete (CRC), a comparative analysis of economic and environmental benefits between CRC and ordinary Portland cement concrete (OPCC) is not explored. In this paper, a quantitative meta-analysis between CRC and OPCC is conducted to explore optimized design strength, and a comparative analysis of the economic and environmental benefits of the two materials is undertaken. Considering cost price as the economic index and CO2 emissions per cubic meter of concrete as the environmental index in the materialization stage, CRC and OPCC were compared with different mix designs to achieve grades of similar strengths. Upon replacing less than 20% of natural fine aggregates in concrete with crumb rubber, while retaining the cement content, an increase of 6% in the cost price was achieved for CRC with 30–40 MPa strength grade. Apart from the aspect of mining and transportation of natural aggregates, the reduction of CO2 emissions by means of CRC adoption was verified in the treatment process of waste tire incineration. The results show that CO2 emissions from CRC decreased by 15–17% when compared with OPCC for 30~40 MPa grade concrete. The research conclusion can serve as a theoretical basis for the engineering application of CRC with the same strength, and make certain contributions to the industrial application of crumb rubber aggregates and the sustainable treatment of waste tires.

Research on Layered Steel Fiber Reinforced Concrete Mix Ratio Design Based on Orthogonal Test

The aim of this study was to investigate the effect of different mix ratios on the mechanical properties of steel fiber-reinforced concrete (LSFRC) and to determine an optimum mix ratio. The effects of four factors, namely, fly ash content, volume fraction of steel fibers, water–cement ratio, and sand rate, on the mechanical properties of LSFRC were investigated through orthogonal experiments. The microstructure of LSFRC at different mix ratios was analyzed using scanning electron microscopy (SEM), and an optimal mix ratio was derived. The results showed that the water–cement ratio and the volume fraction of steel fibers were the main factors affecting the mechanical properties of LSFRC. When the water–cement ratio was 0.38 and 0.42, the combined mechanical properties of concrete were superior. Steel fiber content between 0.6% and 1% had a significant effect on the splitting tensile strength of concrete. The effect of sand rate on compressive and splitting tensile strengths was consistent, with a significant effect on both at a sand rate of 40%. In terms of microstructure, 20% fly ash content promotes the hydration of concrete. The optimum LSFRC mix ratio determined was 0.42 water–cement ratio, 0.6% steel fiber content, 40% sand rate, and 20% fly ash content. Experimental verification using this mix ratio showed that the compressive, flexural, and split tensile strengths were increased by 3%, 19%, and 33%, respectively, when compared to ordinary concrete.

BEARING CAPACITY OF BEAMS UNDER SHORT-TERM LOADS USING THE DIAGRAM OF CONCRETE DEFORMATION IN THE APPEARANCE OF THE FIFTH DEGREE POLYNOM

The theoretical determination of the load-bearing capacity of reinforced concrete beams under short-term loads using the concrete deformation diagram in the form of a fifth degree polynomial and its comparison with the results of experimental studies is considered. In the calculations of reinforced concrete structures using the deformation model of sections, the bending moments are calculated relative to the neutral line, which is located at a distance from the extreme fiber of the compressed concrete and limits its height. In the DBN of Ukraine, it is proposed to describe the concrete deformation diagram by a polynomial of the fifth degree or by a fractional-rational dependence, which was proposed and substantiated by the State Research Institute of Building Structures. Under these conditions, the theoretical bearing capacity of the reinforced concrete beam was obtained, which was also found experimentally. The authors conducted experimental studies of the load-bearing capacity of three series of beams of different types (three identical samples in each series): Series I - beams made of ordinary concrete; II series - steel-reinforced concrete beams; III series - beams of combined section, in which the lower (stretched) height zone is made of steel fiber concrete, and the upper (compressed) zone is made of ordinary concrete. Fiber, the total volume of which was 1%, was uniformly added to the composition of the concrete mass for the II and III series of samples during mixing. A comparison of the theoretical bearing capacity of a reinforced concrete beam with its value obtained experimentally shows that the theoretical value is quite significantly (1.36 times) higher than the experimental value.

Evolution of LWAC–OC interfacial properties during sulfate dry–wet cycles: Bonding strength and micro–properties

The interface properties between lightweight aggregate concrete (LWAC) and ordinary concrete (OC) have drawn significant research interest. However, its evolution during sulfate dry–wet cycles has yet to be elucidated. Therefore, the LWAC–OC composite specimens were subjected to 15 cycles of dry and wet cycles test, using 5 wt% sodium sulfate solution. The dry–wet cycling method consisted of complete immersion for 7 days, followed by natural drying for 8 days. Moreover, tests for splitting tensile, direct shear, scanning electron microscopy and microhardness were conducted on the LWAC–OC interfaces at varying numbers of dry and wet cycles. The results showed that the failure mode of specimens changed from mixed cohesive failure to interfacial bonding failure during sulfate dry–wet cycles. Direct shear and splitting tensile strength slightly increased and then markedly decreased as the number of dry–wet cycles increased. The ratio of direct shear strength to splitting tensile strength showed a distinct negative linear relationship with the number of sulfate dry–wet cycles. Moreover, when the number of dry–wet cycles increased, the porosity of interfacial transition zone first decreased and then increased. The mean value of the interfacial micro–hardness first increased and then decreased. Interfacial micro–properties correlated well with bonding strength throughout the process.

Study of the shear bond behavior of a hybrid fiber-reinforced concrete (HyFRC) composite slab

In this study, a new composite slab consisting of a prefabricated hybrid fiber-reinforced concrete (HyFRC) formwork and a cast-in-place ordinary concrete (OC) topping was proposed. The HyFRC was comprised of steel and PVA fibers. The compressive strength and bending strength of the HyFRC were 111.4 MPa and 15.6 MPa, respectively, and the toughness coefficient was 12.1 MPa. Seven full-scale composite slabs including six simply-supported slabs and one two-span continuous slab were tested under four-point bending to study the shear bond behavior. Three different contact surface conditions were considered for the simply supported slabs. Despite the different interface conditions, results showed that the interfacial bond strength between the HyFRC formwork and the OC topping was sufficient to achieve flexural failure. Numerical simulation was used to analyze the interfacial force transfer mechanism and was validated by the experimental data. The validated numerical model was used to study the influence of concrete topping depth and amount of reinforcement on the load-carrying capacity and longitudinal shear stress at the joint surface. The numerical results identified a critical condition of positive effect between reinforcement ratio and OC topping thickness. The peak load of a properly designed composite slab was almost two times that of the corresponding slab with ordinary concrete only, and the deformation capability was also larger. A procedure for calculating the flexural capacity of the composite slab was proposed.

Analysis-oriented stress-strain model for concrete in steel tubed geopolymer concrete (STGC) columns

To alleviate the brittleness of geopolymer concrete and further promote its engineering application for environmental benefits, a novel type of column, i.e., steel tubed geopolymer concrete (STGC) column, has been proposed recently. Note that an accurate axial stress-strain model is necessary for a comprehensive understanding of the compressive behavior of STGC columns. However, the existing analysis-oriented models are all developed for the conventional concrete-filled steel tube (CFST) columns, and the confinement mechanism of steel tubed concrete columns is significantly different from that of concrete-filled steel tube columns since the axial deformation of steel tube and core concrete is not synchronized for steel tubed concrete columns during the loading process due to the discontinuous steel tube. Furthermore, the dilation properties of STGC columns at the initial loading are significantly overestimated by the existing lateral-axial strain models. Besides, steel-confined geopolymer concrete (GPC) experiences a more remarkable softening behavior resulting from the more significant brittleness of GPC than that of ordinary concrete. Thus, the deformation models are proposed in this study and the active-confinement base model is also developed for GPC based on the mechanical characteristics of STGC columns under axial compression. Then a new analysis-oriented model is proposed for steel tubed geopolymer concrete. Comparisons between the theoretical calculations and the test results indicate that the proposed model can provide reasonable predictions for both steel stress evolution and the stress-strain relationship of STGC.

Fabrication of cement-based superhydrophobic coatings with enhanced self-cleaning property, chemical stability, and UV-radiation resistance

Superhydrophobic coatings (SCs) can potentially reduce dust accumulation on the structure surfaces and mitigate environmental corrosion.In this study, a superhydrophobic coating composed of nano-SiO2, N-octyltriethoxysilane, and silane coupling agent was prepared for cement-based structures by green sol–gel method. By means of SEM, FTIR, XRD, EDS, and XPS, it was proved that cement-based superhydrophobic coatings were successfully formed on the surface of cement-based substrate. Two different techniques (brushing and replication) were used for fabricating cement-based superhydrophobic coatings (CBSCs), and their optimum preparation conditions were determined via orthogonal experiments. The obtained results revealed that the contact angle (CA) and sliding angle (SA) of the fabricated SCs reached 153° and 4°, respectively. Furthermore, the CBSCs exhibited outstanding self-cleaning properties and mechanical stability. Moreover, the chemical stability and UV-radiation resistance of the fabricated CBSCs were significantly improved compared with ordinary concrete.

Why sustainable concrete cannot penetrate concrete markets

Several studies have shown that sustainable concrete mixtures could be a solution to reduce the CO2 emissions of concrete while utilizing supplementary cementitious materials (SCMs) that are waste byproducts, including fly ash, metakaolin, and ground granulated blast furnace slag. However, for these sustainable concrete mixtures to be adopted as a replacement for conventional ordinary Portland cement concrete (OPCC), site engineers, decision-makers, and authorities need to be aware of the mechanical and durability properties of these sustainable concrete mixtures. A brief review of the mechanical and durability properties of both geopolymer concrete and alkali-activated cement demonstrates the objective performance relative to OPCC. Then, the results of a survey targeting researchers, site civil engineers, decision-makers, and employees in governmental agencies are presented. The results indicate that even though the mechanical and durability properties of geopolymer/sustainable concrete are recognized, limited awareness and availability present significant challenges to the adoption of sustainability concrete in infrastructure projects. The survey highlights the need for focused marketing efforts to educate decision-makers on the availability as well as mechanical and durability properties of geopolymer concrete. Additionally, it serves as a call for future research to overcome obstacles such as high initial cost, safety concerns, and limited practical applications.

Flexural performance and damage of reinforced fly ash and slag-based geopolymer concrete after coupling effect of freeze-thaw cycles and sustained loading

To better represent field conditions, the bending performance of reinforced geopolymer concrete (GPC) beams after the coupling effect of freeze-thaw cycling and sustained flexural load was investigated. Two types of GPC (G10 and G50) with different content of fly ash and slag were included and compared with ordinary Portland cement concrete (OPC). The mechanical strength of concrete and bond strength of rebars in concrete before and after freeze-thaw cycles were measured. It was found that the frost resistance of G10 was the weakest followed by OPC and G50. Three scenarios of bending tests on reinforced concrete beams were included: (1) control (without freeze-thaw damage); (2) individual freeze-thaw cycling; (3) coupling effect before bending. Rebound tests were conducted to evaluate frost damages at different areas of the beams as the base to analyze bending behaviors of the beams. The failure mode, load-displacement(strain) relationship, ultimate flexural strength, and bending stiffness of beams from bending tests are analyzed. All beams in scenario (1) were dominant in flexural failure. For scenario (2), G10 and G50 failed in debonding failure due to significant reduction in bond strength, while OPC failed in diagonal tension failure as OPC could sustain bond stiffness, thus preventing debonding failure. For scenario (3), damages in GPC were exacerbated, while damages in OPC were limited.

Performance of multi-ribbed composite wall incorporating reactive powder concrete-filled steel tubular columns under axial compression

In this study, axial compression researches of an innovative composite shear wall, named multi-ribbed composite wall incorporating reactive powder concrete-filled steel tubular columns, were conducted using theoretical analyses as well as experimental and numerical investigations. This precast hybrid system embedded reactive powder concrete-filled steel tubular columns as boundary elements of multi-ribbed composite wall. A novel approach, namely the unified strength theory, was adopted in consideration of various materials diversity. The outcomes of unified strength theory were utilized to predict the ultimate compressive capacity of multi-ribbed composite wall equipped with reactive powder concrete-filled steel tubular columns. The proposed theoretical formulas were validated against the experimental results reported in this paper. Despite the fact that the calculated formula with b= 0 was obtained to predict the closest capacity value of the test specimen infilling ordinary concrete. The calculations with different values of b clearly indicated that the intermediate principal stress effect should be rationally considered. Experimental observations suggested that the frame column significantly contributed to improving the compressive performance throughout the entire process and maintained the wall integrity. Meanwhile, finite element models were developed using the ABAQUS program, followed by the elaboration of its numerical implementation. The numerical predictions of ten shear wall specimens infilling reactive powder concrete were found to be reasonably in agreement with the calculated results corresponding to b= 0.5. These findings revealed the characteristics of multiple defensive lines of "block-ribbed column-frame column" under axial compression. Following the successful validation of finite element models, parametric studies were carried out to evaluate the influences of the filled block compressive strength, steel tube wall thickness and height-width ratio. The results show that the axial compression capacity of multi-ribbed composite wall incorporating reactive powder concrete-filled steel tubular columns can be noticeably improved with an increase in block strength and tube thickness. The proposed composite wall demonstrates favorable cooperative working performance and desirable displacement ductility. Subsequently, the primary objective of this pilot study aimed at developing a reliable theoretical calculation formula and conducting numerical simulation verification of the innovative composite wall. The aforementioned conclusions are intended to provide insights for the guidance and optimization of engineering structures.

Bond properties of steel bar with engineered geopolymer composites under monotonic load

AbstractEngineered geopolymer composites (EGC) featuring extraordinary tensile ductility are a potential alternative to engineered cementitious composite. In this study, the local bonding properties of steel bars in EGC were investigated. Monotonic loading tests of the 120 specimens were performed using the pullout test method. The study examined the ultimate tensile strain of EGC, diameter and anchorage length of the steel bar on bond performance. The results showed that the EGC, with an ultimate tensile strain of 4.57%, had the highest peak bond strength. By comparing the test results of rebar to ordinary concrete bond performance provided in several previous literature, it was demonstrated that EGC has superior bond performance with rebar compared to ordinary concrete. Based on this, suggestions were provided for the design of rebar anchorage length in EGC. Finally, a mathematical model suitable for determining the bond–slip curve between EGC and steel bars is proposed.

Study on the Effect of Post-Freezing Mechanical Properties of Polypropylene Fibre Concrete Based on BAS-BPNN

An indoor accelerated freezing and thawing test of polypropylene fibre-reinforced concrete in chloride and sulphate environments was conducted using the “fast-freezing method” with the objective of investigating the damage law of the post-freezing mechanical properties of hydraulic concrete structures and studying the effects of different mixing amounts of polypropylene fibres on the mechanical properties of concrete. Furthermore, in order to reduce the cost of concrete tests and shorten the time required for conducting concrete tests, a backpropagation neural network based on a Beetle Antenna Search algorithm (BAS-BPNN) was established to simulate and predict the mechanical properties of polypropylene fibre-reinforced concrete. The accuracy of the model was verified. The results indicate that the order of improvement in the macro-physical properties of concrete due to fibre doping is as follows: PPF1.2 exhibited the greatest improvement in macro-physical properties of concrete, followed by PPF0.9, PPF1.5, PPF0.6, and PC. When the freezing and thawing medium and the number of cycles are identical, all four assessment indexes (R2, RMSE, SI, MAPE) demonstrate that the four groups of polypropylene fibre concrete exhibit superior performance to the control group of ordinary concrete. This indicates that polypropylene fibre can enhance the mechanical properties and freezing resistance of the concrete matrix, delay the process of freezing and thawing damage to the matrix, and extend the lifespan of the matrix, yet cannot prevent the ultimate failure of the matrix. The application of intelligent algorithms to optimise the parameters of an artificial neural network model can enhance its capacity to generalise and predict the mechanical properties of concrete. In terms of the coefficient of determination (R2), the Beetle Antenna Search algorithm (0.9782) outperforms the Particle Swarm Optimization (PSO; 0.9676), the Genetic Algorithm (GA; 0.9645), and the backpropagation neural network (BPNN; 0.9460). The improved backpropagation neural network based on the Beetle Antenna Search algorithm not only avoids the trap of local optimality but also improves the model accuracy while further accelerating the convergence speed. This approach can address the complexity, non-linearity, and modelling difficulties encountered during the freezing process of concrete. Moreover, it offers relatively accurate prediction outcomes at a reduced cost in comparison to traditional experimental methodologies.

Wear mechanisms of diamond segmenta in cutting of carbon fiber reinforced cement-based composite and optimizing in parameters

Carbon fiber reinforced cement-based composite material (CFRC) is a novel type of composite material that involves the incorporation of carbon fibers into ordinary concrete. This addition effectively enhances the tensile strength, deformation performance, and dynamic load resistance of reinforced concrete structures. Consequently, CFRC has found increasing applications in the construction industry. The objective of this research is to investigate the wear mechanisms of diamond tools during the sawing process of CFRC and offer guidance on cost reduction through the optimization of processing parameters. The wear analysis of diamond segments can be divided into two categories: matrix wear and diamond particle wear. The diamond particles can exist in different states, and the formation of voids resulting from the detachment of diamond particles is considered as a reference point. The analysis reveals that abrasive wear is the main mechanisms of matrix wear in CFRC sawing. The wear resistance is strongly influenced by the proportion of diamond particles in favorable states, which is determined by the applied loads and operating parameters. The proportion of diamond particles exhibits a clear variation with adjustments made to the feeding speed. Notably, an increase in feeding rate results in a significant decrease in the percentage of blunt particles, reducing it from 28% to 6%. To achieve a lower wear rate, a predictive model was established using Design Expert software based on the experimental results. The model demonstrated that a wear rate as low as 268.5 mm/m2 can be achieved with a flywheel speed of 78 r/min and a feeding speed of 90 mm/h. The optimization process, aimed at minimizing wear rate, was successfully carried out without compromising productivity.

Nanotechnology and high-performance concrete: Evaluating mechanical transformations

The High-performance concrete (HPC) is defined by the attained strength and durability that are superior to conservative techniques. The features of ordinary concrete that are achieved at certain times and locations, used to establish the standards for HPC. The use of nanotechnology in HPC is attracted significant attention globally because of its small particle sizes, filling capacities, enormous surface areas and strong macro quantum tunnel property. By adding nanotechnology to HPC, it increases the whole diameters of the cementations matrix, improves cement hydration and raises matrix density. This study provides a review of current developments in HPC and assesses the effects of different nanotechnology on HPC characteristics, to provide an in-depth understanding of the potential of nanotechnology reinforced in HPC. This review evaluates the mechanical characteristics of HPC containing compressive strength (CS) by applying nano calcium carbonate, nano silicon dioxide, nano titanium dioxide and carbon nano tubes. According to findings in this review, introducing different nanotechnology enhances HPC's mechanical properties while decreasing its flexibility. While integrating nanotechnology into HPC for the greatest possible outcomes in construction, review contributes to expand the collection of information in the area of building materials. To provide a low-impact construction material and an ecologically friendly solution, more consideration is required given to nanoparticles' antibacterial, self-cleaning, air depolluting and air-cooling properties. By increasing the reactivity of various fillers, including nanoparticles with other mineral admixtures reduces the quantity of cement needed in concrete.

Potential for Recycling Metakaolin/Slag-Based Geopolymer Concrete of Various Strength Levels in Freeze-Thaw Conditions.

Geopolymer concrete (GPC) represents an innovative green and low-carbon construction material, offering a viable alternative to ordinary Portland cement concrete (OPC) in building applications. However, existing studies tend to overlook the recyclability aspect of GPC for future use. Various structural applications necessitate the use of concrete with distinct strength characteristics. The recyclability of the parent concrete is influenced by these varying strengths. This study examined the recycling potential of GPC across a spectrum of strength grades (40, 60, 80, and 100 MPa, marked as C40, C60, C80, and C100) when subjected to freeze-thaw conditions. Recycling 5-16 mm recycled geopolymer coarse aggregate (RGAs) from GPC prepared from 5 to 16 mm natural coarse aggregates (NAs). The cementitious material comprised 60% metakaolin and 40% slag, with natural gravel serving as the NAs, and the alkali activator consisting of sodium hydroxide solution and sodium silicate solution. The strength of the GPC was modulated by altering the Na/Al ratio. After 350 freeze-thaw cycles, the GPC specimens underwent crushing, washing, and sieving to produce RGAs. Subsequently, their physical properties (apparent density, water absorption, crushing index, and attached mortar content and microstructure (microhardness, SEM, and XRD) were thoroughly examined. The findings indicated that GPC with strength grades of C100, C80, and C60 were capable of enduring 350 freeze-thaw cycles, in contrast to C40, which did not withstand these conditions. RGAs derived from GPC of strength grades C100 and C80 complied with the criteria for Class II recycled aggregates, whereas RGAs produced from GPC of strength grade C60 aligned with the Class III level. A higher-strength grade in the parent concrete correlated with enhanced performance characteristics in the resulting recycled aggregates.

Study on Comparison between Ordinary Concrete and Rubberized Concrete’

Study on Comparison between Ordinary Concrete and Rubberized Concrete’

Self-healing of macroscopic cracks in concrete by cellulose fiber carried microbes

This research introduces a new approach to healing millimeter scale cracks in concrete using Lysinibaccilus Sphaericus Bacteria (LSB) encapsulated in cellulose fibers. Cracking in concrete, particularly macroscopic cracking, can cause premature structural failure and reduce its lifespan, which is a critical industry challenge. While bacteria encapsulated in cellulose fibers have been used to heal cement mortar, the studies are limited to heal much narrower cracks. In this study, we integrate LSB, known for its strong biocalcification abilities, with the protective environment of cellulose fibers, which are renewable and sustainable, for healing millimeter scale cracks in ordinary cement concrete. To understand the healing process, we firstly used a 3D-printed polymeric scaffold for preliminary observations of calcite precipitation, demonstrating the potential of bacteria-induced calcification in a controlled environment before applying these insights to concrete. We then studied the self-healing of concrete. Through mechanical testing, we identified the optimal concentration of cellulose fiber as 0.45 % by volume of mortar. Approximately 2.38 × 108 bacteria were immobilized in each gram of cellulose fibers. With cellulose fiber encapsulated LSB, the test results show up to 25 % increase in compressive strength and split tensile strength. After crack healing, the self-healing concrete still has higher mechanical strength than the undamaged control concrete. Particularly, the self-healing concrete was able to heal cracks up to 2.5 mm wide in fully wet environments and 1.5 mm wide in wet-dry conditions. This research also highlights the resilience of bacteria carried by cellulose fibers against harsh environmental conditions, including high temperatures at 160 °C, ensuring the durability and applicability of the proposed self-healing concrete in diverse climates. Integrating cellulose fibers encapsulated LSB into concrete represents a significant breakthrough in addressing the perennial problem of concrete cracking, offering a promising avenue for constructing durable and maintenance-free structures.

Influences of aggregate gradation on alkali-silica reaction of seawater and sea sand concrete

The application of seawater and sea sand concrete (SWSSC) is beneficial for marine engineering, but the impact of aggregate gradation on its alkali-silica reaction (ASR) remains poorly understood. This study aims to bridge this gap by analyzing ASR products, pore characteristics and expansion rate of specimens. The test results reveal that ordinary concrete (OC) exhibits an inhibitory effect on ASR in comparison with to SWSSC. The 14-day expansion of ordinary concrete and SWSSC with the same aggregate gradation are 0.130 % and 0.212 %, showing potential and high risk of ASR, respectively. Moreover, particle size and gradation of aggregate are the key factors influencing the ASR degree of SWSSC. Compared with coarser aggregate, specimens with finer aggregate consume more K+ and Ca2+ ions, generate more ASR-P1, form less porosity, and produce a larger expansion. Additionally, specimens with gap-graded aggregates, as opposed to those with uniform or continuous gradation, show greater consumption of K+ and Ca2+ ions, increased ASR-P1 formation, more harmful pore formation, and a larger expansion. These results offer insights into optimizing aggregate gradation to reduce ASR in SWSSC and improve its durability.

Temperature damage assessment of mass concrete based on the coupling mechanism of hydration-temperature-humidity-constraint factors

Temperature cracking of mass concrete is an important issue affecting the safety of concrete foundations in civil engineering. This problem extends from the construction process of concrete foundations to the operation stage. This study uses low-temperature-rising (LTR) polymers to regulate the hydration process of cementitious materials, and prepares LTR mass concrete. Taking the hydration degree of concrete-cement system as the basic state variable, the multi-factor effects of actual hydration process, temperature, humidity changes, and constraints on mass concrete are comprehensively considered. A concrete temperature-damage model based on the coupling mechanism of “hydration-temperature-humidity-constraints” is established, and the temperature, stress, and temperature damage evolution laws of LTR mass concrete and ordinary mass concrete are calculated. The reliability of the model is verified through field tests. The results show that the finite element method can effectively simulate the development of concrete temperature, stress, and damage degree based on actual working conditions under multi-factor coupling.