Abstract:

The funding characteristics and research evolution of the National Natural Science Foundation of China （NSFC） in the field of concrete structure durability over the past 40 years were systematically analyzed. An analysis of more than 1 300 approved projects was conducted.The results show that the funding scale in this field has experienced a leap through four stages： basic cultivation， demand enhancement， scale expansion， and innovation leadership. The research in this field has the characteristics of environmental responsiveness and regional relevance： the Yangtze River Delta， Pearl River Delta， and northern coastal areas have formed innovation hubs in the fields of chloride ion erosion and steel bar corrosion， while the central and western regions and Northeast China have achieved breakthroughs in aspects such as freeze-thaw/salt corrosion coupling. The funded projects are divided into two categories： material science and structural engineering. The material science category focuses on the performance evolution and deterioration mechanism of cement-based materials， and the structural engineering category focuses on the degradation mechanism of the service performance of concrete structures throughout their whole life cycle—both provide theoretical support for the construction of major projects. In the future， low-carbon， durable， and high-performance materials and structural systems will be developed， the application of artificial intelligence will be promoted， zoned planning and collaborative innovation will be deepened， and the exploration of extreme service conditions will be expanded.

Abstract:

It is easy to induce calcium corrosion for cement paste in a carbonated water-rich environment， which becomes a severe threat to its service performance. In order to properly reflect the dissolution-diffusion process of CO₂ in water and its interaction with cement minerals， a reactive transport model（RTM） was therefore developed， which was then utilized to study the spatial and temporal distribution of cement minerals， solutes and pore structure during groundwater erosion. In this way， the deterioration behavior of hardened cement paste can be thus assessed. The results show that generated calcite precipitation will fill in available pore space when the content of dissolved CO₂ in water is low， which prevents further loss of calcium ions. Once its concentration is larger than 14.00 mmol/L， the calcite begins to decompose due to an increased acidity of pore solution， resulting in an accelerated deterioration progress of cement paste.

Abstract:

Macroscopic and microscopic creep tests were conducted， combined with low-field nuclear magnetic resonance ¹H-NMR and nitrogen adsorption tests， to systematically investigate the creep characteristics and humidity response mechanisms of hardened cement paste under different internal relative humidity conditions （10%-98%）. The results indicate that as the internal relative humidity decreases， the creep deformation of hardened cement paste gradually decreases， the creep modulus significantly increases， and the characteristic time shortens accordingly. Within the relative humidity range of 10%-98%， the relationship between creep modulus and relative humidity conforms to a parabolic function. Based on this， a creep modulus-relative humidity dependency model was established， demonstrating good predictive capability. With decreasing internal relative humidity， both the pore volume and water saturation of gel pores and transition pores show a declining trend. The creep modulus exhibits a strong negative linear correlation with the water saturation of gel pores， while its relationship with the water saturation of transition pores follows a parabolic pattern.

Abstract:

This study employed the pore network modeling （PNM） method to describe the pore structure of cementitious materials， while also considering the moisture distribution within the pore network. Further， a 2D numerical model for chloride diffusion based on the pore network was developed. The feasibility of the model was verified by comparing it with the third-party tests. By considering pore structure characteristics including porosity， pore size distribution， connectivity， and tortuosity， this model studied the influence of the microstructure on the chloride diffusion process. Results show that the diffusion performance of chloride highly depends on the saturation degree and the characteristics of pore structure. The decrease in porosity and the reduction in average pore size can lead to a decrease in the chloride diffusion coefficient of cementitious materials. Moreover， there is an inverse relationship between tortuosity and connectivity. When connectivity is below 0.7 and tortuosity exceeds 1.5， the relative diffusion coefficient of chloride is less than 0.2， indicating a significant improvement in the chloride erosion resistance of the material.

Abstract:

To address the demand for building exterior wall self-cleaning coatings to simultaneously possess dual functions of photocatalytic degradation of pollutants and hydrophobicity， a core-shell structured ZnCdS@SiO₂-CF composite was developed. Zn_0.5Cd_0.5S semiconductor was synthesized at room temperature via a stepwise ion exchange-co-precipitation method. Subsequently， a SiO₂ shell was constructed through an in-situ hydrolysis coating technology， and long carbon-fluorine chains were grafted onto the shell， forming a micro-nano rough core-shell composite with low surface energy modification. The results show that Zn_0.5Cd_0.5S exhibits a large specific surface area； after 6 h of hydrolysis coating with tetraethyl orthosilicate ， the composite exhibits the highest roughness and can effectively suppress the recombination of photogenerated carriers. Spray test results show that a coating amount of 16.33 mg/cm² endows the cement-based self-cleaning coating with superhydrophobicity， acid-base corrosion resistance， and mechanical stability. Under visible light irradiation， the coating still maintains a degradation rate of 79.52% for methylene blue， which is 2.52 times that of titanium dioxide.

Abstract:

The effects of thermal cycling on the compressive strength， splitting tensile strength， water absorption and pore structure of C45， C60 and C90 concrete under 40-90 ℃ and 40-200 ℃ were investigated. The mechanisms by which thermal cycling affects the mechanical properties and microstructure of concrete were elucidated. The results demonstrate that under 40-90 ℃ thermal cycling， the hydration process of concrete is accelerated， leading to a significant enhancement in mechanical properties. After 90 cycles， the compressive strength of C45 concrete increases by up to 41.5%. Under 40-200 ℃ thermal cycling， the quantity of certain hydration products decreases， and the strength initially improves but then declines with increasing cycles. Due to lower hydration degrees and a more porous internal structure， the mechanical property of low-strength-grade concrete is more significantly affected by thermal cycling. As the number of thermal cycles increases， the concrete structure becomes looser， the number of internal pores rises， and the proportion of harmful and multi-harmful pores within the pore structure increases.

Abstract:

A discrete element numerical model was established based on the volume expansion theory， and the damage and failure process of the rock-concrete interface under the coupled action of freeze-thaw cycles and dynamic three-point bending load was systematically simulated. The results show that the crack propagation of the rock-concrete interface undergoes three stages： slow growth， rapid growth， and unstable failure； the fracture toughness has a significant dependence on the loading rate. At low loading rates （v=0.5-1.0 m/s）， the fracture toughness exhibits the characteristic of “slight increase-sharp decrease”. When the loading rate increases to 1.3-1.7 m/s， the fracture toughness exhibits a “sharp increase-sharp decrease”trend. The growth rate of the stress intensity factor shows a general downward trend with increasing number of freeze-thaw cycles.

Abstract:

Coated treatment was conducted on sludge gasification slag using a blended mixture of cement and fly ash， and the treated slag was utilized as coarse aggregate for lightweight aggregate concrete. The influences of coarse aggregate type and volume fraction on the performance of concrete were systematically investigated. A two-dimensional finite element model of concrete was established to simulate the damage distribution and stress-strain curve during concrete failure under uniaxial compressive conditions. The results show that the sludge gasification slag retains its lightweight characteristics after being coated with the cement and fly ash， while its cylinder compressive strength significantly increases from 2.5 MPa to 6.1 MPa. When the volume fraction of coarse aggregate is 40%， the concrete with coated sludge gasification slag aggregate exhibits the smallest damage area and the optimal compressive performance.

Abstract:

To address the rapid stiffness degradation and significant residual deformation of concrete-filled steel tube columns under seismic loading， a novel composite column， the ultra-high performance concrete-filled steel tube （UHPCFST） reinforced with steel-FRP composite bars （SFCB）， was proposed. A series of cyclic loading tests was conducted to evaluate its seismic performance. The results indicate that， compared to UHPCFST columns reinforced with either steel bars or basalt fiber-reinforced composite bar， those columns reinforced with SFCB exhibit intermediate levels of load-bearing capacity， ductility， energy dissipation， and residual deformation. Both methods of increasing the SFCB reinforcement ratio and replacing conventional concrete with ultra-high porformance contrece（UHPC） in the steel tube can enhance the seismic performance of the composite column. Moreover， a high axial compression ratio benifits the load-bearing capacity， initial stiffness， and energy dissipations， but accelerates stiffness degradation and reduces ductility. When the SFCB reinforcement ratio increases from 3% to 4%， the comprehensive seismic performance of the composite column improves by 21%， while material costs rise by only 5%. Therefore， increasing the SFCB reinforcement ratio is the most cost-effective approach to enhancing the seismic performance of composite columns.

Abstract:

Based on 687 sets of concrete compressive strength data， the standard uncertainty and expanded uncertainty were evaluated using the measurement uncertainty assessment method. By integrating the conversion results of the expanded uncertainty interval， the characteristics of strength distribution， the determination of single value eligibility， and the comprehensive assessment method were systematically analyzed. The results indicate that the compressive strength interval can effectively quantify the impact of uncertain factors， and there is a significant correlation between the average strength interval and the probability interval of the normal distribution. The method for determining single value eligibility can provide a quantitative basis for the uncertainty in critical value determination. The comprehensive assessment method can account for the differences between the specimens submitted for inspection and the actual testing conditions， providing an important basis for enhancing the rigor and applicability of engineering quality assessment.

Abstract:

A chemical thermodynamic model to predict the mineral composition of stabilized soil under varying water contents， stabilizer dosages， and incorporation methods （internal and external mixing） was established. Based on the simulation results， key mix proportion parameters were identified and used to prepare representative samples. The macroscopic compressive strength， XRD patterns， and ²⁹Si NMR spectra were analyzed to investigate the response mechanisms of the mix proportion parameters. The results demonstrate that the thermodynamic model reliably predicts the evolution of mineral phases in stabilized soil. The stabilizer dosage significantly influences the formation of reaction products， while water content has a relatively minor effect. The strength development is primarily governed by the total amount of reaction products， the n（Al）/n（Si） ratio， the proportion of hydrated aluminosilicate gel in the cementitious system， and the mean chain length of all gel phases. These factors should be incorporated into thermodynamic simulations to improve the accuracy of mix proportion design.

Abstract:

Rice fermentation residue and liquid were used in desulfurization gypsum blocks as admixtures. The results indicate that these admixtures effectively increase the standard consistency water requirement， retard setting time and enhance water resistance of desulfurization gypsum. Specifically， after adding 0.9% rice fermentation residue and liquid， the softening coefficients increase by 41.9% and 35.4%， respectively， while the water absorption rates decrease by 57.9% and 57.0% compared to the blank control group. Although rice fermentation residue and liquid negatively affect the mechanical properties of desulfurization gypsum， the degree of mechanical property reduction is comparable to that of common salt based admixtures. Additionally， rice fermentation products influence the growth of the （002） plane of calcium sulfate dihydrate without forming covalent bonds with the crystals， and the morphology of dihydrate gypsum crystals remains largely unchanged.

Abstract:

The effects of the content of square and flat rubber particles on the shear characteristics of rubber-sand mixtures were investigated through indoor direct shear tests. A discrete element method（DEM） model was established to reveal the macro-meso mechanical responses of rubber-sand mixtures， in which real river sand scanning data files and a particle clustering method were used to simulate sand particles and rubber particles， respectively. The results indicate that the internal friction angles of both types of rubber-sand mixtures decrease with the increase of rubber particle content， reaching a maximum value when the rubber particle content is 5%. Under the same rubber particle content， square rubber-sand mixture has higher shear strength， while flat rubber-sand mixture has a more significant dilatancy inhibition effect. The force chain network of rubber-sand mixture is dominated by “sand-sand” contacts， which bear the main stress. Compared to flat rubber-sand mixture， the square rubber-sand mixture has a higher proportion of “sand-sand” contacts， which is macroscopically manifested as higher shear strength.

Abstract:

To realize the multi-objective performance of concrete proportion design， the optimal ranges for slag content， fly ash content， and water/binder ratio in C40 ready-mixed concrete were studied though single-factor experiments. The response surface methodology was employed to construct quadratic polynomial regression models， with which the effects of different slag content， fly ash content， and water-binder ratio on the slump and compressive strength of concrete were systematically investigated. Furthermore， the non-dominated sorting genetic algorithm（NSGA-Ⅱ） combined with the technique for order preference by similar to ideal solution（TOPSIS） comprehensive evaluation method was applied to achieve the multi-objective optimization design of concrete mix proportion. The results demonstrate that the regression models of concrete slump and 28 d compressive strength established by response surface methodology have correlation coefficients of 0.944 7 and 0.960 4 respectively， indicating good prediction accuracy. The fly ash content has a significant influence on the slump， while the compressive strength is mainly affected by the water-binder ratio. After optimization， the optimal mix proportion scheme is obtained as follows： slag content of 8.66%， fly ash content of 25.00%， and water-binder ratio of 0.34. The relative error between the predicted values and the experimental values is less than 5%.

Abstract:

Based on an actual project in Qingdao， basalt fiber reinforced polymer（BFRP） anti-floating anchors were applied to the anti-floating project of coastal underground structures， and on-site creep performance tests on the BFRP anti-floating anchors were carried out. Through real-time testing of anchor bar and anchor soil displacement， the evolution characteristics of load-displacement of BFRP anti-floating anchor bar were clarified， and the spatial and temporal distribution law of the internal force of anchor bar of BFRP anti-floating anchor bar was revealed. The results show that the displacement of anchor bar in BFRP anti-floating anchor bar is affected by the load level and loading time， and the displacement of anchor bar and anchor soil grows with the increase of loading time showing two stages of initial creep and steady state creep. At the maximum load level， the axial force of the anchor bar shows a non-linear distribution along the depth， which decays gradually with the increase of depth， and tends to zero at the deepest point. At the same depth， the axial force decreases gradually with loading time. The interfacial shear stress between the anchor bar and anchor soil first increases and then decreases with the increase of depth， and the peak stress appears at approximately 0.75 m from the orifice. The peak stress decreases with the increase of loading time， and the shear stress attenuation is concentrated in the range of 0.7-1.7 m.

Abstract:

The traditional Le Chatelier test for soundness detection is inaccurate and cannot characterize local strain features of the paste, which limits the investigation of soundness-failure mechanisms. In this study, full-field displacement and local strain of cement paste with varying magnesium oxide contents after boiling were analyzed using digital image correlation (DIC), and the correlation between DIC and Le Chatelier test results was investigated. The results show that as magnesium oxide content increases, the perimeter and area geometric parameters of specimens after boiling characterized by DIC increase linearly. The local strain non-uniformity of specimens increases significantly, elevating cracking and failure risks. The geometric parameters measured by DIC are highly correlated with the expansion measured by Le Chatelier test, with a Spearman correlation coefficient of 0.988-0.999 (p < 0.01). These results demonstrate that DIC provides reliable and accurate soundness detection while capturing local strain characteristics.

Abstract:

Self-healing of cracks in cement-based materials is critical to structural durability, but practical water conditions significantly influence microbial mineralization efficacy.This study evaluated the crack-repair capabilities of three microbial systems (urease-producing mixed microorganisms, aerobic mixed microorganisms, and polygenic mixed microorganisms) in mortar specimens under static (varying water head levels) and dynamic (different flow velocities) water environments. Key parameters including crack-sealing width, mechanical property recovery, and mineralization characteristics were comprehensively analyzed. Results demonstrated that both static water head and dynamic flow velocity markedly affected repair performance, with the polygenic mixed microorganisms system exhibiting superior anti-interference capacity. Under static/dynamic conditions, its maximum sealed crack widths reached 0.747 mm and 0.526 mm, respectively, while 28 d compressive and splitting tensile strength recovery rates improved to 70.23% and 82.82%. The study confirms that synergistic remediation by polygenic mixed microorganisms enhances self-healing efficiency in complex water environments, offering an optimized solution for engineering applications.

Abstract:

In this study, geopolymer anticorrosion coatings consisted of fly ash and slag were prepared by regulating the modulus and Na2O content of alkali activator; their basic properties, chloride penetration resistance, and corrosion protection performance were systematically investigated. The results showed that the geopolymer coatings prepared with fly ash/slag mass ratio of 7:3, water-binder ratio of 0.35, water glass modulus of 1.5 and Na2O content of 6 wt.% (AAFS1), as well as modulus of 2.0 and Na2O content of 5 wt.% (AAFS2), exhibited high hardness, rapid curing, and high alkalinity, with complete drying time ≤2.5 h and pH>13.2. Although the chloride penetration resistance of the prepared geopolymer coatings was lower than epoxy resin coatings, they demonstrated superior corrosion protection performance for the reinforcement: the corrosion initiation time of the reinforcement was extended from 12 h to 130 h, the critical chloride concentration was increased by 16 times, and the corrosion inhibition efficiency reached 87% at 28 days. The excellent corrosion protection of the prepared geopolymer coatings was attributed to their dual mechanisms of physical barrier and chemical passivation.

Abstract:

To address the issue of thermal shrinkage cracking in mass concrete caused by cement hydration heat accumulation, and the limited availability of fly ash in remote areas, this study employed tuff powder (TP) as a substitute supplementary cementitious material in low-heat cement (LHC). A combined macro-performance and micro-mechanism approach was adopted to systematically investigate the effect of TP dosage on the early hydration and crack resistance of LHC. Low-field nuclear magnetic resonance was used for real-time monitoring of the hydration process, complemented by microstructural characterization techniques such as XRD, SEM, and TGA to reveal the mechanisms of hydration retardation and product optimization. Temperature-stress tests were conducted to comprehensively evaluate the anti-cracking performance. The results show that TP significantly delays the early hydration process of LHC, reducing the heat release and adiabatic temperature rise (approximately 21% reduction with 20% TP), thereby effectively mitigating temperature shrinkage stresses. Although early compressive strength slightly decreases, the 3d flexural-to-compressive strength ratio increases notably, indicating enhanced material toughness. Microscopically, TP reduces Ca(OH)? content and promotes later pozzolanic reactions, thereby optimizing the microstructure. This study innovatively elucidates the synergistic mechanism of TP in improving the early crack resistance of LHC concrete from a multi-scale perspective linking hydration, microstructure, and stress development, providing a theoretical basis for its application in dam projects in remote regions.

Abstract:

To address the resource wastage and environmental issues associated with the stockpiling of volcanic rock processing tailings in the Tengchong region, this study utilized volcanic sand (V-sand) with an apparent density of 2651 kg/m-3 as an internal curing agent. Saturated surface-dry (SSD) V-sand was used to substitute natural sand at volumetric replacement ratios of 40%, 60%, and 100% to prepare cement mortars, and the efficacy and mechanism of internal curing were investigated. The results indicate that the pore structure of the V-sand is characterized predominantly by macropores with an average pore diameter of 194.20 nm, exhibiting a water desorption ratio of 89.2% at a relative humidity (RH) greater than 93%. Macroscopically, the compressive and flexural strengths of the cement mortars under both standard and drying curing conditions consistently increased with the SSD-V-sand replacement ratio at various ages. Specifically, at 100% replacement, the 28-day compressive strength under standard curing increased by 13.5% compared to the control group. Furthermore, the incorporation of SSD-V-sand significantly mitigated the autogenous shrinkage of the cement-based materials; at 100% replacement, early-age autogenous shrinkage was reduced by 89.1% relative to the reference group. Microscopically, the SSD-V-sand promoted the formation of hydration products with a low Ca/Si ratio and high Al/Ca ratio in the vicinity of the aggregate interface. Consequently, the average micro-hardness of the interfacial transition zone (ITZ) between the V-sand and the cement paste increased by 23.6% compared to the reference group. These findings demonstrate that volcanic tailings sand can serve as an excellent functional material for mitigating autogenous shrinkage and enhancing the strength of high-strength and high-performance cement-based materials.

Abstract:

Tibetan villages in Western Sichuan, serving as typical representatives of traditional raw earth construction, rely heavily on the performance of their core masonry material—raw soil slurry—which directly impacts the structural stability and durability of the buildings. This study focuses on the raw soil slurry from the Tibetan villages in Danba, Sichuan. Through physical property tests, mix ratio optimization, and mechanical performance experiments, it systematically analyzes the shrinkage characteristics, bulk density, compressive strength, splitting tensile strength, and uniaxial compressive stress-strain relationship of the raw soil slurry. The results indicate that: the volumetric shrinkage rate of the raw soil slurry increases with an increasing water-to-soil ratio, while its uniaxial compressive strength decrease with an increasing water-to-soil ratio. When the water-to-soil ratio is 0.38, the 28-day compressive strength of cube specimens is 1.16 MPa with a coefficient of variation of 1.38%, and the splitting tensile strength is 0.18 MPa. All specimens exhibited a "conical" failure pattern, and their stress-strain curves followed a "parabolic" shape. Based on the characteristics of the stress-strain curves under uniaxial compression, a constitutive model for raw soil slurry under uniaxial compression is proposed. This model provides theoretical support for researching the seismic performance of Tibetan village structures constructed using raw soil slurry masonry.

Abstract:

This study conducted a 180-day seawater erosion test, combined with the determination of chloride ion concentration and pH measurement, to systematically analyze the chloride ion erosion behavior of concrete under three flow velocities of 0 m/s (static), 0.2 m/s, and 0.4 m/s. Based on the experimental data, an exponential decay model was used for high-precision nonlinear fitting (R2 > 0.99) to determine the boundary chloride ion concentration (C?), and a diffusion-convection coupling model was established. The results show that seawater flow increases the chloride ion concentration at the concrete surface, and this effect weakens with the increase of erosion depth; the flow conditions cause the surface pH to decrease, promoting the dissolution of hydration products and enhancing the invasion of chloride ions; the convection effect caused by the flowing water environment is essentially different from the diffusion transmission under static water pressure in the dominant mechanism. The research results provide theoretical support and quantitative basis for the durability design of concrete structures in different service environments (splash zone, deep underwater zone) of marine engineering.

Abstract:

In this study, fly-ash phase change cenospheres (FPCC) were combined with textile-reinforced concrete (TRC) to develop a thermal-storage TRC material (FPCC-TRC) with integrated structure and function, while chopped polyvinyl alcohol (PVA) fibers were used to enhance its mechanical properties. The effects of FPCC content (0%, 10%, 15%, 20%) and chopped fibers on the mechanical properties of FPCC-TRC were investigated, including analysis of cracking behavior, failure processes, failure modes, and stress-strain responses under uniaxial tensile loading. The results indicate that matrix achieves excellent heat storage capacity after incorporating FPCC. 20%FPCC matrix’s melting enthalpy and crystallization enthalpy are 20.6 J/g and 19.9 J/g, respectively. However, the mechanical properties degrade with the increase in FPCC content: 20%FPCC matrix’s flexural strength and compressive strength of the matrix are 5.6 MPa and 29.6 MPa, with respective decreases of 34.9% and 40.4%. Incorporation of chopped fibers can effectively enhance the mechanical properties of the matrix, with a more pronounced improvement in flexural strength. XRD test results indicate that no new substances are generated after FPCC incorporation, and SEM images demonstrate excellent compatibility between FPCC and matrix. FPCC does not alter the failure process and failure mode of TRC, with the damage dominated by the fracture of the fiber mesh. Chopped fibers reduce crack spacing and control crack width. FPCC-TRC’s initial cracking stress and peak stress decrease with increasing FPCC content, while peak strain increases. Chopped fibers enhanced matrix-textile stress transfer synergy, increasing initial cracking and peak stresses and reducing peak strain.

Abstract:

This study proposes the use of intrinsically magnetic fly ash cenosphere (FAC) as lightweight aggregate. The particle?size dependence of their magnetic properties was systematically analyzed, and their magneto?responsive rheological behavior in fresh lightweight concrete was investigated. Experimental results show that the magneto?rheological response exhibits distinct modes, corresponding to comprehensive enhancement, decoupling between static and dynamic responses, and selective improvement in dynamic performance, respectively. Mechanistic analysis indicates that these differences originate from the interparticle magnetic forces, which are governed by particle size, and from the coupled effects among magnetic force, paste film thickness, and particle gradation. This work elucidates the intrinsic linkage between particle size, magnetic performance, and rheological properties of FAC, providing a theoretical foundation for developing performance-controllable, lightweight aggregate concrete.

Abstract:

Although alkali-activated materials exhibit advantages such as corrosion resistance and rapid setting, their inherent brittleness and susceptibility to cracking limit their application in coastal concrete structure repair projects. This study developed a novel semi-aqueous semi-oleophilic epoxy resin and incorporated it into alkali-activated materials with a polymeric cement ratio (P/C) of 5%-30% (mass percentage of the new epoxy resin to cementitious materials) to prepare composite repair materials. The physical and mechanical properties as well as microstructural mechanisms were systematically investigated. Results demonstrated that the composite epoxy resin achieved a tensile strength of 24MPa and a fracture elongation of 5.8%, representing 2.67 times and 1.32 times those of conventional E51 epoxy resin, respectively. At a P/C ratio of 15%, a continuous and uniform interpenetrating network (IPN) structure formed within the alkali-activated material. The workability of the repair material increased to 86 cm, the 56-day drying shrinkage rate decreased to 0.06%, and the water absorption rate stabilized at 5.6% after 84 hours. The flexural strength, tensile strength, and normal tensile bond strength reached 9.8MPa, 7.15MPa, and 2.6MPa, respectively. No surface cracks were observed after natural light-heat aging. Microstructural analysis revealed that the IPN structure effectively prevented and inhibited crack formation and propagation by filling pores, bridging cracks, and reducing crystallinity, thereby synergistically enhancing the physical and mechanical properties and durability of the alkali-activated repair material.

Abstract:

The interfacial adhesion performance between asphalt and aggregates during high-temperature mixing processes is primarily determined by the surface free energy properties of molten asphalt. To enhance measurement accuracy, this study refined the surface free energy determination methodology using the sessile drop method, with particular focus on computational model optimization and substrate selection. Comparative evaluations demonstrated the equation-of-state model exhibited greater computational stability and reliability compared to traditional component method approaches. Polytetrafluoroethylene (PTFE) plates were confirmed as the optimal substrate for sessile drop measurements, owing to their minimal surface free energy and outstanding chemical resistance. The optimized protocol enabled establishment of temperature-dependent surface free energy prediction models for two representative asphalt types in molten state, along with blend prediction equations for asphalt mixtures containing varying proportions of aged and virgin materials. All models achieved excellent goodness-of-fit (R2>0.95), providing important references for evaluating the adhesion between asphalt and aggregates during high-temperature mixing processes.

Abstract:

To address the challenge of rapid performance degradation of asphalt pavement crack sealants under long-term low temperatures and freeze-thaw cycles in cold regions, this study systematically conducted durability tests under thermo-oxidative aging, freeze-thaw cycles, and their coupled effects, based on the SBS/basalt fiber composite formulation (SBS 10%, extracted oil 13.09%, fiber 4%) previously optimized by the team using response surface methodology [1]. The results show that after severe thermo-oxidative aging (190°C, 5 h), the compressive elastic recovery rate of the optimized material decreased by only 3.05%, and the tensile strength retention rate reached 87.42%, which is significantly superior to commercial products. After three freeze-thaw cycles, its adhesion strength retention rate still reached 63.7%, and under tensile testing at -30°C, it exhibited typical toughness failure characteristics, avoiding sudden brittle fracture. Micro-mechanism analysis revealed that the three-dimensional interpenetrating network formed by basalt fiber with SBS and rubber powder can effectively maintain interfacial integrity under aging and freeze-thaw coupled stresses, and suppress microcrack propagation through stress redistribution, which is the fundamental reason for its excellent low-temperature durability. This study deepens the understanding of the full-lifecycle service behavior of fiber-reinforced modified crack sealants in cold regions, providing direct performance evidence and mechanistic support for their engineering applications.

Abstract:

To address the deterioration of concrete structures in cold regions under the coupled action of freeze-thaw(FT) cycles and impact loads, this study systematically investigated the enhancement mechanism of the dynamic mechanical properties of Polyvinyl alcohol-basalt hybrid fiber reinforced concrete (PVA/BF-RC). The performance evolution of PVA/BF-RC was compared with that of plain concrete (PC) after exposure to 0 to 100 FT cycles. An electro-hydraulic servo testing machine and a Split hopkinson pressure bar (SHPB) apparatus are employed to analyze their static and dynamic compressive properties, mass loss patterns, strength degradation, Dynamic increase factor (DIF), and failure modes.The results show that PVA/BF-RC exhibits superior resistance to combined freeze-thaw and impact actions. After 100 FT cycles, the mass loss rate of PVA/BF-RC is merely 0.22%, compared to 4.54% for PC; its static compressive strength loss is also significantly reduced to 40.64% from PC"s 71.03%. Under an impact velocity of 13 m/s, the peak stress of PVA/BF-RC reaches 42.66 MPa, which is 41.4% higher than that of PC, and the fluctuation of its DIF with increasing freeze-thaw damage is only about 0.1. By effectively suppressing crack propagation and spalling, PVA/BF-RC significantly enhances the concrete"s freeze-thaw durability and dynamic impact resistance. Based on the experimental data, a freeze-thaw deterioration function, C(n), and a dynamic strength computational model were established, providing a basis for predicting the mechanical behavior of PVA/BF-RC after freeze-thaw damage.

Abstract:

To investigate the properties and optimal dosage of polyurethane-modified asphalt, this study employs Materials Studio molecular dynamics simulation software to construct molecular models of base asphalt and modified asphalt with polyurethane contents of 3.67%、7.13%、10.33%, respectively. Through simulation analysis of microscopic performance parameters such as diffusion coefficient、physical modulus and so on, analyzes the influence of polyurethane dosage on the microscopic properties of asphalt. Subsequently, combined with the three major index test、bending beam rheometer (BBR) test and dynamic shear rheometer (DSR) test, the optimal dosage of polyurethane was determined. The Molecular dynamics simulation results indicate that: Under ambient conditions, with the increase in polyurethane dosage, the cohesive energy density exhibits a continuous upward trend, the physical modulus increases first and then decrease; when the dosage reaches 7.13%, the absolute value of binding energy is maximized and the system achieves optimal stability; simultaneously, the diffusion coefficient is minimized, indicating favorable bonding between the modifier and asphalt, the comprehensive performance of asphalt reaches the optimum. Based on the comprehensive macroscopic test results of asphalt, the optimal dosage of polyurethane was determined to be 8%. The research method of this paper provides a new idea for the performance study of other modified asphalt materials.

Abstract:

Flocculants are commonly used additives in wet-process manufactured sand production, and their residues can adversely affect the performance of cement-based materials. In this study, cationic polyacrylamide (CPAM), anionic polyacrylamide (APAM), nonionic polyacrylamide (NPAM), and polyaluminum chloride (PAC) were introduced into manufactured sand at mass fractions of 0.03‰ ~ 1.2‰ relative to the sand mass. The effects of different flocculant residues on the fluidity, setting time, and mechanical properties including compressive and flexural strength of manufactured sand mortar were systematically investigated, and the underlying mechanisms were analyzed using zeta potential and mercury intrusion porosimetry (MIP). The results show that all four flocculants reduce mortar fluidity. All four flocculants resulted in a decrease in mortar flowability. PAM-based flocculants delayed setting and suppressed early hydration reactions through adsorption–encapsulation and steric hindrance effects. In contrast, PAC promoted the formation of AFt owing to the release of Al3+ during hydrolysis, thereby exhibiting a mild accelerating effect on setting. The reduction in 7-day strength is attributed to residual flocculants, which led to a significantly higher proportion of pores with diameters ≥ 50 nm compared with the reference mixture.

Abstract:

To address the limitations of existing concrete durability prediction models, such as low accuracy and insufficient engineering applicability, this study established five machine learning models—Light Gradient Boosting Machine (LightGBM), Categorical Boosting (CatBoost), Extreme Gradient Boosting (XGBoost), Random Forest (RF), and Artificial Neural Network (ANN)—based on the 10-year marine exposure test in Zhanjiang, to predict the chloride diffusion property of high-performance concrete under marine environments. The results indicate that the CatBoost model achieved the best prediction performance, with an R2 of 0.9143, and its Mean Absolute Error (MAE), Root Mean Square Error (RMSE), and Mean Absolute Percentage Error (MAPE) were all lower than those of the other models, demonstrating superior accuracy and robustness. SHAP-based interpretability analysis revealed that the water-to-binder ratio had the greatest influence on the chloride diffusion performance of high-performance concrete in marine environments, followed by cement content, exposure time, and silica fume content, while fly ash content had the least impact. Furthermore, compared to the traditional decay model based on Fick’s second law, the CatBoost model significantly improved prediction accuracy.

Abstract:

To study the bond-slip performance of steel reinforced concrete strengthened by nano-SiO?, the specimens were tested under cyclic reversed loading. The failure modes, characteristic bond strengths and degradation of interfacial bond performance of the specimens were analyzed. The formulas for calculating bond strength and the bond-slip constitutive model were established. The results indicate that the peak bond strength of the specimen sprayed with 10% nano-SiO? on the steel surface is 28.38% higher than that of the control specimen, and the failure mode transforms from bond failure to bond-slip failure. The dense C-S-H gel layer formed at the bond interface by spraying nano-SiO? enhances interfacial integrity, thereby reducing cumulative damage. Formulas for calculating the characteristic bond strength of the specimens are derived through multiple regression analysis, and the prediction accuracy reaches 91%. A bond-slip constitutive model of the steel-concrete interface modified by nano-SiO? is established, which shows agreement with the experimental curves.

Abstract:

As the most widely used construction material in human history, concrete provides the fundamental technological foundation for advancing modern structural engineering toward super-tall, long-span, and lightweight systems. The development of high-strength and super-high-strength concrete represents a key frontier in both material science and structural performance enhancement. This review systematically elucidates the intrinsic origins and governing mechanisms of concrete strength from four perspectives: the C–S–H gel phase, reinforcing phase, interfacial phase, and pore structure. It further summarizes recent progress in design theories and technical strategies for achieving super-high-strength concrete, emphasizing approaches such as phase densification, microstructural optimization, and multiscale strengthening. Finally, the review highlights current research focuses and emerging directions in multi-phase synergy, interfacial regulation, and data-driven intelligent design, aiming to provide theoretical insight and technological guidance for future breakthroughs in the strength limits of concrete.

Abstract:

Steel fiber reinforced concrete (SFRC) specimens were firstly pre-damaged through freeze-thaw cycles, then the performance evolution of the pre-damaged SFRC exposed to chloride solution drying–wetting (D-W) cycles was investigated, including chloride ion transport, pH distribution, and mechanical properties such as compressive strength, and flexural properties. The results indicated that the pre-damaged SFRC exhibits potential corrosion risks under chloride D-W cycles, due to an increase in internal chloride content and a decrease in near-surface pH value. However, after 180 dry-wet cycles, the compressive strength increased by 9.5%–24.1%, flexural strength increased by 10.2%–29.7%, and its flexural toughness and stiffness were also significantly enhanced. Under the action of chloride D-W cycles, the continuous hydration of cementitious materials repaired the damage of SFRC induced by freeze-thaw cycles, and the positive reinforcement effect of steel fiber corrosion (interface strengthening and crack filling) further improved the mechanical properties of concrete.

Abstract:

To investigate the mechanical response characteristics of aluminum alloy expansion tubes under low-velocity impact, specimens with a length of 200 mm, cross-sectional dimensions of 63×6.5 mm, and an expansion ratio of 1.16 were designed and fabricated based on the testing of aluminum alloy material properties. Drop-weight impact tests were conducted at three velocity conditions of 8 m/s, 10 m/s and 12 m/s. Combined with 3D-DIC measurement technology and motion analysis techniques, the strain field of the expansion tube and the evolution characteristics of the cone die speed were obtained, respectively, to investigate the correlation between strain and expansion velocity. The results show that the elongation of 6063-T6 aluminum alloy ranges between 22% and 25%, demonstrating excellent plastic deformation capability. The strain development of the aluminum tube during expansion is stable, exhibiting a steady-state plastic deformation process. The peak strain rates of the expansion tube are all below 100 s-1 and decay rapidly with the progression of expansion. Both circumferential and longitudinal strain rates show a highly significant linear correlation with the cone die motion velocity.

Abstract:

The preparation of powder polycarboxylate superplasticizer by centrifugal spray drying process was discussed. The powder solid content(by mass) of the product can reach 99%. Through infrared spectroscopy the carbonyl group has been shown to be partly decomposed during the drying process which has only limited influence on the performance of the powder with the result that its performance is at the same level compared to the liquid superplasticizer. Based on single factor experiments, the major parameters affecting the drying process were discussed and the appropriate process conditions were obtained, e.g. the import air temperature of drying chamber must be controlled at 180220℃；the spray drying feed temperature controlled at 2040℃, and solid content of polycarboxylate superplasticizer fed is in the range of 20% to 60%.

Abstract:

The purpose of this paper is to use dynamic characterization model to evaluate the dynamic process of asphalt aging and compare the pros and cons of different asphalt. First, the RTFOT aging tests at different aging time for four kinds of asphalt are carried out and the aging test data are fitted with dynamic characterization model. As a result, the aging parameters and aging equation of penetration, ductility, softening point and viscosity of different asphalt are determined. Then, grey relational evaluation method is used to evaluate the anti-aging performance of different asphalt, which setting the aging parameters L and r of penetration, ductility, softening point and viscosity as the evaluation indexes. The results show that: the aging rate of penetration, softening point, ductility of asphalt reaches the peak at the beginning and becomes smaller as the variation of aging time and balances at last; The aging process of asphalt can be described accurately by dynamic characterization mode and parameters L and r can be a good characterization of aging degree and aging rate; The sort of anti-aging properties of the four asphalt is determined as following: the indoor modified asphalt is better than matrix 90 asphalt and better than SBS modified asphalt and better than matrix 70 asphalt.

Abstract:

The development of free deformation and internal moisture in cement paste, mortar and concrete were experimentally investigated. The results show that the deformations of cement paste, mortar and concrete at early age all exhibit plastic swelling at initial several hours after casting and then shrinking with a gradually reduced rate. The end point of swelling may be corresponding to the transformation point of plastic state to solid state and this point can be defined as setting time of the cement based materials. The development of shrinkage starting from setting point of the three kinds of cementitious materials exhibits at first a fast developing stage(stage Ⅰ) and is followed by a relatively slow developing stage(stage Ⅱ). The restraint effect of aggregates on shrinkage is significant only in the stage Ⅱ. In stage Ⅰ a similar shrinkage values are observed on the three kinds of materials. The development of moisture inside cement paste, mortar and concrete can be described as a vapor saturated stage with saturated moisture followed by a stage in that internal moisture is gradually reduced. The shrinkage developed within stage Ⅱ can well correlate to the reduction of internal moisture.

Abstract:

The mix design of manufactured aggregate was proposed based on the Dinger-Funk grading model. The mass relationship between binder and water for concrete with manufactured aggregate was determined by modifying the Bolomey’s formula. The paste thickness was introduced to establish the volume relationship between aggregate and paste. In addition， the stone powder in manufactured sand was considered as a component of the paste. Finally， the mix design method of concrete with manufactured sand was proposed and verified with concrete of different strength grades. The results show that the workability of concrete can be regulated by the paste thickness. The compressive strength of concrete and the diffusion coefficient of chloride have no obvious correlation with the paste thickness， with the water to binder ratio being the main factor regulating the hardened performance of concrete. The proposed mix design method can be used to quantitatively design concrete with manufactured aggregate for various performance requirements.

Abstract:

The effect of modulus, mass fraction and temperature of sodium silicate solution(SS) on the rheological characteristics of SS and geopolymer slurry(GS) were analyzed by means of viscometer and rheometer. Meanwhile, the effect of SS modified by ultrasonic on the workability of GS was studied. The re sults show that the viscosity of SS for 2.2 modulus get the minimum value in ambient temperature(1825℃), but the effect of modulus on viscosity of SS is gradually weaker with the raise of temperature. When SS is in the true solution(high ionized) zone(modulus<1.8), the difference of GS viscosity of different SS modulus is little, while in the water glass(SiO2 polymerized) zone(modulus>2.2), the viscosity of GS increases sharply with the increase of modulus of SS. With increasing of the mass fraction of SS, both viscosity of GS and SS are all increased.The viscosity of GS gets the minimum value at 30℃ in different SS modulus. The SS modified by ultrasonic could improve the fluidity of GS and increase the compressive strength of geopolymer.

Abstract:

To improve the unfavorable engineering performance of sand and make it applicable for riverbank slopes， foundation， and road reinforcement， a method for modifying sand using polymers and fibers is proposed. Through unconfined compressive strength tests and numerical simulations， the strength characteristics and deformation failure modes of the modified sand are analyzed. The results indicate that the combined use of polymers and fibers can effectively enhance the compressive strength of sand， and the compressive strength of the modified sand increases with the dosage of polymers and fibers. The maximum compressive strength of the modified sand is 414.53 kPa， with the optimal recommended dosages of fibers and polymers being 0.6% and 4.0%， respectively. The addition of fibers forms a force chain network in the sand， thereby increasing the stress transmission paths and effectively delaying the development of micro-cracks within the sand. The incorporation of polymers creates a membranous substance that intertwines with the fibers， forming a new network structure， which significantly improves the deformation resistance of the sand.

Abstract:

The apparent morphology， mass loss rate， relative dynamic elastic modulus， compressive strength and pore structure of blue bricks after freeze-thaw cycle were studied. The relationship between fractal dimension and compressive strength， porosity and frost resistance was established based on fractal theory. The results show that with the increase of freeze-thaw cycles， the small pores on the surface of the blue brick deteriorate into large pores and gradually extend into cracks， resulting in an increase in the mass loss rate， and a decrease in the relative dynamic elastic modulus and compressive strength. After freeze-thaw cycle， the internal pores of the blue brick have obvious fractal characteristics， and the fractal dimension is distributed between 2.964 2 and 2.982 7. The fractal dimension of blue brick after freeze-thaw cycle is positively correlated to compressive strength and negatively correlated to porosity， and its fractal dimension is also highly correlated with frost resistance. The fractal dimension can be used to evaluate the microscopic pore structure change of the blue brick， and can also reflect the influence of the complexity of the pore structure on the macroscopic properties of the blue brick after freeze-thaw cycle. The research results provide a basis for the protection and durability damage of ancient architectural blue bricks in cold regions.

Abstract:

Taking the ancient building wall of Longshengzhuang in Inner Mongolia as the research object， the damage and failure law of ancient building blue bricks under freeze-thaw cycles were investigated by digital image correlation（DIC） technology. Two-factor—damage degree factor and damage localization factor were used to characterize the uniaxial compression damage process of ancient building blue bricks. Based on the two-factor damage evolution curve， a damage evolution model was established under different freeze-thaw cycles. The results show that the failure process of ancient building blue bricks under uniaxial compression can be divided into four stages—initial damage closure stage， linear elastic damage stage， elastic-plastic damage stage and plastic damage stage. With the increase of freeze-thaw cycles， the strain concentration on the surface of blue brick increases， resulting in a decrease in bearing capacity. Freeze-thaw cycles will shorten the linear elastic stage in the two-factor curve. At the same time， the damage evolution model established by the two-factor can effectively reflect the damage evolution process of the ancient building blue brick material under the action of freeze-thaw cycles.

Abstract:

The effect of the molar ratio（n（MgO）∶n（MgSO₄）∶n（H₂O）） in the raw materials on the mechanical properties and deformation characteristics of modified magnesium oxysulfide（MMOS） cement was studied， and the mechanism was analyzed by testing techniques， such as X-ray diffraction（XRD）， scanning electron microscope（SEM）， Fourier transform infrared spectroscopy（FTIR） and thermogravimetric analysis（TG）. The results show that the compressive strength and flexural strength of MMOS cement matrix shows an increasing trend with the increase of water-sulfur ratio and oxygen-sulfur ratio. The specimen with a molar ratio of 10∶1∶12 has the highest compressive and flexural strength. The deformation of MMOS cement specimens with different molar ratios during the period from completion of pouring to 56 days of curing is mainly expansion deformation. The total deformation of MMOS cement specimens shows a decreasing trend with the increase of water-sulfur ratio and oxygen-sulfur ratio， while the autogenous deformation shows a decreasing trend with the increase of water-sulfur ratio and a first increasing and then decreasing trend with the increase of oxygen-sulfur ratio. The MMOS cement specimens with different molar ratios exhibit differences in expansion deformation， mainly due to the different contents of hydration products Mg（OH）₂， 5·1·7 phase （5Mg（OH）₂·MgSO₄·7H₂O） and unreacted MgO phase in the hardened matrix. When the content of Mg（OH）₂ decreases and the content of 5·1·7 phase increases， the expansion deformation phenomenon of MMOS cement specimens weakens， while their flexural strength and compressive strength are improved.

Abstract:

By comparing the strength and durability differences between 3D printing concrete（3DPC） and casting concrete in different test directions， the anisotropic characteristics of the hardened properties of 3DPC and its dependence on the resting time were explored. The results show that the hardened properties of 3DPC have certain anisotropy， and the mechanical properties and impermeability in the vertical direction are higher. The anisotropy of hardened properties is related to the weak bonding interface between printing layers and the distribution of pores and defects in the concrete matrix. The bonding property of interlayer interface is obviously weakened when resting time is prolonged. The durability of different printing layers of 3DPC is different， the density of the upper layer of concrete is lower， and the diffusion rate of the aggressive medium is faster.

Abstract:

Based on the mathematical characteristic analysis of the dynamic modulus principal curve of asphalt mixture， the viscoelastic evaluation system of reclaimed asphalt mixture was established， and the physical parameters of viscoelastic behavior were also proposed. The viscoelastic difference between tensile and compressive directions was compared， the fatigue characteristics of reclaimed asphalt mixture in tensile and compressive direction were studied， and the relationship between fatigue properties and viscoelastic physical properties was established. The results show that， compared with the new asphalt mixture， the reclaimed asphalt mixture is elastic rather that viscoelastic， but it is effective viscoelastic enough under compression mode， and elastic rather that viscoelastic under tensile mode. Under the same loading mode （whether compressive or tensile）， only the viscoelastic physical property parameter R_eve has a high linear correlation with fatigue life N_f. When the loading mode is different， the linear relationship between R_eve and N_f can not be established.

Abstract:

The surface roughness parameters of Q690 high strength steel and weld joint specimens were assessed through microscopic scanning tests to investigate the dynamic changes in corrosion morphology characteristics of high strength steel（HSS） within the ocean splash zone corrosive environment. These investigations encompassed the analysis of parameters such as the maximum height of surface peaks S_p， the maximum depth of surface valleys S_v， the skewness of surface profiles S_sk， and the kurtosis of surface profiles S_ku over varying periods of corrosion. Power function regression analyses and comparative assessments were conducted for each of these parameters. The results indicate that considering the differences in the scanning area of base material and weld joint of Q690 high strength steel， the corrosion degrees and characteristics can be accurately determined by analyzing the variation process of roughness parameters with corrosion time， so as to provide a new approach for damage assessment of domestically produced high strength steel in marine environments.

Abstract:

To understand the deterioration mechanism of CFRP/steel interface properties under extreme hot and humid environment， 12 of CFRP/steel double lap specimens using Sika-30 adhesive were prepared. These specimens were immersed in simulated seawater at 70 ℃ for different time for tensile shear test. The results show that the failure mode of these specimens were less affected by the soaking time. The average shear strength of the CFRP/steel interfaces increased first and then decreased with the soaking time. After soaking for 90 days， the average shear strength of the CFRP/steel interfaces decreased by 35.6% compared with that of unsoaked specimen.

Abstract:

Vulcanized eucommia ulmoides gum modified asphalt（VEUGMA） was prepared by natural plant-based eucommia ulmoides gum（EUG）， and the microstructure and pyrolysis process of VEUGMA were studied. The results show that VEUGMA is of lower penetration， higher softening point， larger ductility and viscosity， better deformation resistance at high temperature and cracking resistance at low temperature than matrix asphalt. Compared to matrix asphalt， VEUGMA has larger number and smaller size of honeycomb structures， lower root mean square roughness， greater adhesion， higher pyrolysis temperature， and less CO₂ and CO release. The modification effect is the best when 6% EUG and 3.5% sulfur （calculated by EUG quality） are added to the matrix asphalt.

Abstract:

Leachate sludge was solidified by using sulphoaluminate cement（SAC） and municipal solid waste incineration fly ash as cementitious materials. The composite curing effect and curing mechanism of cement and fly ash were explored through an unconfined compressive strength test， leaching toxicity analysis and microscopic test. The results show that when the cement content is not less than 20%， 28 d unconfined compressive strength of the cement solidified sample meets the landfill strength requirements. Fly ash is an excellent auxiliary curing agent for cement solidified leachate sludge， and its enhancement effect on the unconfined compressive strength of cement solidified samples has an optimal dosage. 10% fly ash can replace 10% cement to achieve a better curing effect. The samples with 30% or 40% cement + 15% fly ash can meet the requirements of landfill strength and leaching toxicity at the same time.

Abstract:

Nitrite intercalation hydrotalcite（NO₂-LDH） was prepared by roasting and reduction method， and its effect on adsorption， dispersion and enhancement of superplasticizer were studied. The results show that the layer spacing and crystallinity of the NO₂-LDH are slightly lower than that of protocarbonate type Mg-Al hydrotalcite. There is anion exchange between NO₂-LDH and superplasticizer， which reduces the adsorption and dispersion effect of superplasticizer. The decreasing degree of dispersion effect of superplasticizer increases with the increase of NO₂-LDH content. NO₂-LDH has no obvious effect on the flexural strength of mortar mixed with superplasticizer， but the compressive strength is slightly increased. The effect of NO₂-LDH on the dispersion of naphthalene superplasticizer is greater than that of polycarboxylic acid superplasticizer.

Abstract:

Municipal solid waste incinerator(MSWI) fly ash was successfully used as a raw material in sintering sulphoaluminate cement clinker in the laboratory. The clinkerization process, morphology and compositions of the clinker were investigated. The hydration properties of sulphoaluminate cement and the toxicity leaching characteristics of heavy metals were also studied. The results show that the good quality clinkers in which C4A3S and C2S are presented as major phases can be sintered by using the MSWI fly ash as raw material, and the optimal amount of MSWI fly ash in the raw mix is about 30%. Microstructure of produced clinker was loose and lacunary and it appeared to be irregular tiny crystal. The sulphoaluminate cement with reasonable strength can be prepared by grinding the clinker with appropriate amount of gypsum. Porosity and mean pore diameter of harden cement paste decrease with the curing age. The results also indicate that the concentrations of all the investigated elements in the leachates are far below the regulatory limit up to 28 d, and the produced cements would not present a leaching hazard to environment.

Abstract:

Basalt fiber（BF） was modified by coupling agent（KH550） and nano-SiO₂， and the effect of BF surface modification on the mechanical properties of basalt fiber reinforced concrete（BFRC） was studied. The results show that after modification with KH550 and nano-SiO₂， the surface of BF forms C—H bonds， and the vibration peak corresponding to Si—O—Si bonds becomes stronger. When the amount of nano-SiO₂ is 3% of the mass of BF， the morphology of BF changes most significantly， and the mechanical strength and crack resistance of modified BFRC are significantly higher than those of ordinary BFRC. Under the bridging effect of KH550， nano-SiO₂ can effectively enhance the bonding strength between fibers and the concrete matrix， thereby improving the mechanical strength and crack resistance of BFRC

Abstract:

Based on an improved vertical expansion rate（ε_v） testing method， the development of ε_v of high-strength cementitious grouting material for wind power project within 0-24 hours and 1-7 days was obtained. The effects of the proportions of mineral admixtures as well as expansive agents on ε_v， fluidity and mechanical strength of grouting material were experimentally investigated. Results show that a typical developing characteristic with “four stages” is observed in the curves of ε_v-time of grouting material during 0-24 hours. With the increase of silica fume percentage in the range of 0%-20%， the fluidity of grouting material decreases gradually， and the peak value of ε_v firstly increases and then decreases from casting to 24 hours. Plastic expansive agent（PEA） dominants the development of ε_v within 24 hours. Furthermore， calcium sulphoaluminate-calcium oxide expansive agent（HP-CSA） is added， the peak value of ε_v decreases， the 24 h-value decreases， and the 3 h-value increases， which is beneficial to the control of the difference between the 24 h-value and 3 h-value. During the age of 1-7 days， the expansive efficiency of HP-CSA can well be promoted by PEA with addition of 0.03%. And the vertical autogenous shrinkage can generally be “compensated” by HP-CSA with the addition percentage not less than 6%， resulting in a grouting material with a net expansion during the period either 0-24 hours or 1-7 days. Relay effect in time and synergistic effect in outcome on expansion regulation for the grouting material are observed when PEA and HP-CSA composite are used， and if an appropriate dosage is found， a fine regulation on ε_v is well achieved in stages within 7 days. In addition， with the increase of the composite expansive agent， the initial and 30 mins values of fluidity of the grouting material shows little change， and the compressive strength at 28 days first increases and then decreases. Within the scope of this study， PEA at 0.06% and HP-CSA at 6% is comprehensively the optimal dosage composite.

Abstract:

Modified mineral adsorbents were prepared by changing the content of silicon oxide， alumina oxide， and calcium oxide in kaolin. The mass， morphology and phase transformation of the modified mineral absorbents were analyzed at 900-1 450 ℃. The results show that amorphous aluminosilicates are the main component of mineral adsorbents at 900 ℃. At 1 200 ℃， amorphous aluminosilicates transform into mullite and cristobalite. Increasing silicon oxide content inhibits this transformation， while increasing alumina content decomposes into corundum phase and improves the chemical stability of the adsorbent. Calcium oxide reacts with active silicon aluminum to form calcium feldspar. When the temperature exceeds 1 200 ℃， an appropriate increase in silicon oxide content can reduce the melting sintering of mineral adsorbents and reduce the release of Pb. However， increasing alumina oxide and calcium oxide contents eliminate and intensify the melting sintering of mineral adsorbents， and has little effect on the release of Pb. The research can provide guidance for improving the solidification of heavy metals in the collaborative disposal of cement kilns.