Abstract:

As the most widely used construction material， concrete provides a fundamental technological basis for modern structural engineering toward super-tall， long-span， and lightweight systems. The pursuit of high-strength and super-high strength concrete remains a key direction for enhancing both material performance and structural capacity. This review systematically summarizes the intrinsic origins and key influencing factors of concrete strength from four perspectives： the calcium silicate hydrate（C-S-H） gel phase， reinforcing phase， interfacial phase， and pore structure. It further reviews current design theories and technical approaches for super-high strength enhancement of concrete. Finally， the review discusses current research focuses and future directions， aiming to provide theoretical references and technical support for breakthroughs toward the strength limits of concrete.

Abstract:

This study utilized low-field nuclear magnetic resonance （LF-NMR） to in situ investigate the water distribution， water migration， and pore structure evolution during setting and hardening of cement paste incorporating MgO expansive agent （MEA） at different temperatures （5，20，60 ℃） and water-binder ratios （m_w/m_b=0.35，0.45）. Results show that MEA accelerates total signal decay， improves internal water distribution， reduces free water content， and increases the proportion of micro capillary water. Those effects can be enhanced with the increased temperatures. After hydrating for 6 h of cement paste prepared with m_w/m_b of 0.35， the addition of MEA increases the content of micro-capillary water at 60 ℃ by 6.4 and 2.9 times compared to that at 5 ℃ and 20 ℃， respectively. The presence of MEA raises the weighted average relaxation time （T¯₂） and reduces the fractal dimension， which shows an enhanced influence with the increased temperature. At 6 h， T¯₂ increases by 0.19， 0.22， 0.29 ms at 5， 20， 60 ℃， respectively， and is more pronounced at m_w/m_b=0.45.

Abstract:

To investigate the accelerated corrosion behavior of calcium aluminate cement（CAC）-based materials in NH₄Cl solutions， accelerated corrosion tests were conducted on CAC paste/mortar specimens in three NH₄Cl concentrations （0.5， 1.0 and 2.0 mol/L）， using corrosion tests in deionized water as the control group. The variations in specimen mass loss， compressive strength， phase composition， pH value of the immersion solution， and Ca²⁺ concentration with immersion time were studied. The effects of different NH₄Cl concentrations on the corrosion behavior of CAC paste were analyzed through X-ray diffraction（XRD）， XRD Rietveld quantitative analysis， thermogravimetric -derivative thermogravimetry analysis（TG-DTG）， and ethylene diamine tetraacetic acid（EDTA） titration. The results show that as the immersion time increases， the hydration degree of the specimens continuously improves. In NH₄Cl solutions， the strength of CAC mortar specimens significantly decreases after 92 days of immersion， and the mass loss of CAC paste and the rate of Ca²⁺ concentration increase in the immersion solution are significantly higher than those in the control group. With increasing NH₄Cl concentration， the corrosion rate of CAC hydration products gradually increases， resulting in a gradual degradation of the material properties.

Abstract:

To improve the early stability and thermal insulation performance of foamed concrete， a crosslinking system was prepared with 2-acrylamid-2-methylpropanesulfonic acid， N， N'-methylenebis（acrylamide）， ammonium persulfate and sodium bisulfite. The influence of crosslinking polymer content on the rheological properties， thermal conductivity and pore structure of foamed concrete was investigated. The pore structure of foamed concrete was characterized by X-ray computed tomography（X-CT） technology， the heat transfer behavior of foamed concrete was simulated by COMSOL software， and the heat transfer mechanism of foamed concrete was revealed. The results show that the addition of crosslinking polymer shortens the initial setting time and increases the apparent viscosity， plastic viscosity， dynamic yield stress and thixotropy of paste. The increase of pore volume and the number of small pores in foamed concrete can extend the heat transfer path， thereby enhancing its thermal insulation performance.

Abstract:

To investigate the performance evolution of steel fiber reinforced concrete （SFRC） under the coupling of chloride and freeze-thaw dry-wet cycles， the damage and deterioration of SFRC were treated by chloride freeze-thaw cycles. The chloride transport， pH value distribution， compressive strength and flexural strength of the freeze-thaw damaged SFRC exposed to chloride dry-wet cycles（DW） were investigated. The results indicate that the internal chloride content of freeze-thaw damaged SFRC increases and the near-surface pH value decreases under chloride DW， implying potential corrosion risks. However， after 180 times of chloride DW， the compressive strength and flexural strength of freeze-thaw damaged SFRC specimens increase by 8.7%-19.4% and 10.2%-29.7%， respectively， and their flexural toughness and stiffness also improve significantly. The continuous hydration of cementitious materials repairs the damage of SFRC induced by freeze-thaw cycles under chloride DW. Moreover， the positive reinforcement effect of steel fiber corrosion （interface strengthening and crack filling） further improves the mechanical properties of concretes.

Abstract:

Uniaxial， biaxial， conventional triaxial and true triaxial compression tests were conducted on plastic concrete to investigate the effects of different loading conditions on the dilatation characteristics and failure mechanism of the specimens. The results indicate that under different loading conditions， the specimen exhibits dilatation before reaching its peak， which is a precursor to specimen failure. The dilatation value of the sample is related to the material properties and the size of the lateral limit. The greater the strength of the material， the smaller the dilatation value. The stronger the lateral constraint， the greater the dilatation value and strength of the specimen. After the peak of the stress-strain curve of the dilated sample， the deformation shows softening or plasticization characteristics， while the stress-strain curve of the non-expanded sample shows hardening characteristics after the peak. The lateral strain expansion of the specimen first occurs in the direction of lower lateral stress. When the dilatation occurs in the direction of higher lateral stress， the specimen is about to dilate. The dilatation of lateral strain can be used as a basis for predicting the dilatation of the specimen.

Abstract:

Separated Hopkinson pressure bar， digital speckle correlation method and scanning electron microscopy were combined to study the dynamic splitting tensile damage characteristics of steel fiber recycled aggregate concrete（SFRAC）， observe its crack evolution process and microstructure， and analyze the relationship between SFRAC microstructure and macroscopic mechanical properties under dynamic splitting tensile load. The results indicate that the peak stress of SFRAC significantly increases with the increase of strain rate， with a dynamic increasing factor of 1.5-2.2 within the impact stress range of 0.08-0.12 MPa. Steel fibers can significantly improve the dynamic splitting tensile strength of recycled concrete. The optimal steel fiber content is 1.0%， and the increase in dynamic splitting tensile strength can reach 41.60%. When the replacement rate of recycled aggregate is 50%， the splitting tensile strength of SFRAC with 1.0% steel fiber content is equivalent to that of ordinary concrete. Steel fibers can delay the formation of high strain areas and reduce local damage to specimens. Because of the decrease and uneven distribution of hydration products in the cement paste， the gel particles of recycled concrete increase， and the bonding performance of the matrix is weakened. Steel fibers undergo plastic deformation under impact and form effective anchorage， suppressing crack propagation and thereby enhancing the macroscopic strength of SFRAC.

Abstract:

A temperature-humidity intelligent alternating environment chamber and a high hydrostatic pressure loading device were used to simulate plateau low-humidity curing conditions and hydrostatic pressure effects， and the performance evolution of concrete under the combined effect of plateau low-humidity environment and hydrostatic pressure was systematically investigated. The results show that low-humidity curing significantly enhances the water absorption property of concrete while reducing its axial compressive strength and elastic modulus. As hydrostatic pressure increases， the water absorption rate of concrete increases， the degradation of axial compressive strength intensifies， and the elastic modulus exhibits a degradation pattern of “first decreasing and then increasing”. The shear strength of concrete increases approximately linearly with increasing curing temperature and decreasing hydrostatic pressure. An increase in hydrostatic pressure aggravates the degradation of mechanical strength of concrete. The negative effect of high hydrostatic pressure is more significant under low-temperature （not exceeding 0 ℃） curing， whereas the strengthening effect of high-temperature curing can effectively offset the negative effect caused by increased hydrostatic pressure.

Abstract:

To investigate the improvement mechanism of hybrid fibers on the corrosion resistance of reactive powder concrete （RPC） subjected to the coupling effect of chloride salt-freeze-thaw， reinforced RPC samples with different types（steel fibers（SFs）， polypropylene fibers（PPFs）， rice straw fibers（RSFs））and contents of fiber were prepared. The effect of SFs， PPFs， and RSFs on the corrosion resistance of RPC were systematically studied through mass loss rate， relative dynamic elastic modulus， Tafel polarization curves， and electrochemical corrosion rate. The results show that hybrid fibers significantly enhance the corrosion resistance of RPC. After respectively selecting the optimal mixture from single-fiber， double-fiber， and triple-fiber hybrid schemes， the performance can be ordered as follows： 2% SFs+1% PPFs+1% RSFs>3% SFs+1% PPFs>3% SFs. With the optimal hybrid fiber mixture， the mass loss rate of the specimen decreases by 85.33% compared to the control group， the relative dynamic elastic modulus increases by 61.25%， and reduction rate of the reinforcement corrosion rate decreases by 59.19%. The incorporation of rice straw fiber not only improves the compactness of the matrix but also exerts a synergistic effect of fiber hybridization， effectively delaying the process of chloride attack and freeze-thaw damage.

Abstract:

To predict the chloride diffusion behavior of high-performance concrete in marine environments， Five machine learning models—light gradient boosting machine（LightGBM）， categorical boosting（CatBoost）， extreme gradient boosting（XGBoost）， random forest（RF）， and artificial neural network（ANN）—were developed using a dataset from a 10-year in-situ marine exposure test in Zhanjiang city. The results show that among the five machine learning models， CatBoost demonstrates superior robustness and accuracy， achieving the highest determination coefficient（0.914 3） and the lowest error（mean absolute error， root mean square error， and mean absolute percentage error）. Shapley additive explanations（SHAP） identifies the water-to-binder ratio as the most critical determinant of chloride diffusivity， followed by cement content， exposure time， and silica fume content， whereas fly ash content shows the least significance. Furthermore， the proposed CatBoost model offers significantly higher prediction accuracy than that of the traditional standard calculation methods based on Fick’s law.

Abstract:

To study the interface bond-slip performance of nano-SiO₂ strengthened steel reinforced concrete， the specimens were tested under cyclic reversed loading. The failure modes， characteristic bond strengths and degradation mechanism of interfacial bond performance of the specimens were analyzed. The formula 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-SiO₂ 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 formes at the bond interface by spraying nano-SiO₂ enhances interfacial integrity， thereby reducing cumulative damage. Formulas for calculating the characteristic bond strength of the specimens are derived， and the prediction accuracy reaches 91%. A bond-slip constitutive model of the steel-concrete interface modified by nano-SiO₂ is established， which shows agreement with the experimental curves.

Abstract:

To investigate the mechanical response characteristics of aluminum alloy expansion tubes under low-velocity impact， based on material property testing of 6063-T6 aluminum alloy， expansion tube specimens with dimensions of ϕ63.0×6.5 mm×200.0 mm and an expansion ratio of 1.16 were designed and fabricated. Drop-weight impact tests were conducted at impact velocities of 8， 10， and 12 m/s， combined with 3D digital image correlation （3D-DIC） and motion analysis techniques. The strain field distribution and the evolution characteristics of the cone die speed were systematically obtained， and the correlation between strain and impact velocity was analyzed. The results show that the aluminum alloy exhibits excellent plastic deformation capability， with an elongation of 22%-25%. The strain develops steadily during the expansion process， demonstrating favorable steady-state plastic deformation characteristics. The absolute value of circumferential and longitudinal peak strain rate of specimens are 90.2， 61.8 s^-1， respectively， rapidly decreasing as expansion progresses， and exhibit a significant linear relationship with the cone die motion velocity.

Abstract:

To mitigate the performance degradation of soil under cyclic climatic changes， recycled tire polymer fibers （RTPF） were employed to improve stabilized carbonate saline soil. Uniaxial compression test， desiccation cracking test， and computed tomography scanning test were conducted to systematically investigate the improvement effect and fiber-reinforcing mechanism of RTPF on stabilized carbonate saline soil under dry-wet cycles. The results indicate that the optimal improvement in compressive strength is achieved with 0.2%-0.4% RTPF fibrils and 1%-2% fiber bundles. The incorporation of RTPF effectively reduces the porosity and desiccation crack area of stabilized carbonate saline soil， thereby diminishing mass and strength loss after dry-wet cycles while increasing the deformation modulus. Both the strength deterioration degree and deformation modulus exhibite exponential relationships with 0-10 dry-wet cycles.

Abstract:

5·1·7 type basic magnesium sulfate whiskers （5·1·7W ） were synthesized at room temperature using different active MgO and magnesium sulfate heptahydrate as raw materials， with sodium citrate as an additive. The whiskers were characterized using X-ray diffraction（XRD）， scanning electron microscopy（SEM）， transmission electron microscopy（TEM）， and thermogravimetry-differential scanning calorimetry（TG-DSC）. The prepared 5·1·7W was used to modify polyvinyl chloride （PVC）， and its effects on the mechanical properties and flame retardancy of PVC were studied. The results indicate that when the sodium citrate content is 3%， the seed crystal content is 2%， the mass fraction of magnesium sulfate solution is 10%-15%， and MgO with a specific surface area <45 m²/g is employed， high-purity monodisperse 5·1·7W whiskers with a diameter of 100-150 nm， length of 10-20 μm， and an aspect ratio of 66.7-200.0 can be prepared. After high-temperature calcination， 5·1·7W can be transformed into MgO whiskers. 5·1·7W exhibits excellent improvement on the mechanical and flame-retardant properties of PVC.

Abstract:

To address the problem of strength degradation and cracking of geopolymers after exposure to high temperatures, this paper investigates fly ash-slag based geopolymer (FSG) modified by the synergistic effect of basalt fiber (BF) and nano-Al?O? (NA). The mass loss rate, appearance morphology, and residual strength of FSG after exposure to different temperatures (20, 200, 400, 600, 800, and 1000 °C) are analyzed. On this basis, a back propagation neural network (BPNN) prediction model for residual compressive strength is constructed, and genetic algorithm (GA), particle swarm optimization (PSO), and whale optimization algorithm (WOA) are introduced to optimize the BPNN model. The optimal model is determined by comparing prediction accuracy, and the model is validated using error analysis and 10-fold cross-validation. The results show that with the increase in temperature, the mass loss rate of FSG increases, while the residual compressive and flexural strengths first increase and then decrease. At 400 °C, the optimal performance is achieved with the addition of 0.6% BF and 2% NA, where the residual compressive strength and flexural strength reach 53.4 MPa and 8.3 MPa, respectively, which are 36.2% and 33.8% higher than those of the reference group. The coefficient of determination (R²) of the four prediction models, namely BPNN, GA-BPNN, PSO-BPNN, and WOA-BPNN, are 0.954, 0.969, 0.981, and 0.993, respectively. Among them, the WOA-BPNN model exhibits the highest accuracy and stability in predicting the 28-day residual compressive strength.

Abstract:

Abstract: The drying shrinkage deformation of the phosphogypsum slag cement is a key performance indicator of widespread concern. Current research on the drying shrinkage deformation of this system remains very limited. In this study, the effects of phosphogypsum and cement contents on the drying shrinkage behavior of the phosphogypsum slag cement mortar were investigated by using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and nitrogen adsorption. The results show that the drying shrinkage deformation of the phosphogypsum slag cement mortar follows a quadratic function relationship with the phosphogypsum content and cement content. Cement and phosphogypsum exhibit a synergistic effect that increases drying shrinkage and the influence of cement is greater than that of phosphogypsum. the specimen with 20% phosphogypsum, 10% cement, and 70% slag exhibits the minimum drying shrinkage deformation (approximately 620 με at 91 days), which is about 40% of that of the specimen with 60% phosphogypsum, 20% cement, and 20% slag. In addition, the drying shrinkage deformation increases with mass loss rate, and a good linear relationship is observed between them. The drying shrinkage behavior of the phosphogypsum slag cement mortar is closely related to its hydration products and pore structure. When the degree of hydration is low, insufficient formation of hydration products leads to deterioration of pore structure and accelerated moisture migration and evaporation, thereby increasing drying shrinkage. When the degree of hydration is high, the amounts of ettringite and gel hydration products increase. Although ettringite provides an expansion-compensating effect, the increase in capillary pressure induced by pore refinement becomes dominant, resulting in increased drying shrinkage. Keywords: phosphogypsum slag cement mortar; phosphogypsum; drying shrinkage; mass loss rate; pore structure

Abstract:

The performance evolution of ultra-high-strength concrete (UHSC) incorporating fully manufactured aggregates under the combined influence of multiple mix-design parameters remains insufficiently understood. This study systematically investigated the effects of the water-to-binder ratio, sand ratio, total binder content, cement content, slag content, silica fume content, and steam-curing regime on the compressive strength and chloride diffusion coefficient of UHSC. A quantitative evaluation method based on sensitivity coefficients was proposed to characterize the relative importance of each factor, and multivariate predictive models incorporating seven key variables were established. The results indicate that the water-to-binder ratio is the most influential factor governing both the compressive strength at all curing ages and the chloride diffusion coefficient of UHSC. Increasing the contents of cement, slag, and silica fume significantly reduces the chloride diffusion coefficient, with the degree of influence ranked as slag > cement > silica fume, whereas the effects of the sand ratio and steam-curing regime are comparatively insignificant. The established models exhibited satisfactory predictive performance, with coefficients of determination (R2) ranging from 0.804 to 0.940 for compressive strength at different curing ages and 0.814 for the chloride diffusion coefficient. These findings provide a scientific basis for mix proportion design and performance prediction of UHSC incorporating fully manufactured aggregates.

Abstract:

To elucidate the modification mechanism of highly active calcium carbonate polymorphs on the hydration of calcium sulfoaluminate (CSA) cement, this study established a simplified ye''elimite model to comparatively investigate the differences between vaterite and calcite in terms of heterogeneous nucleation, chemical activity, and phase stability. Characterization via isothermal calorimetry, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that vaterite exhibits a stronger specific adsorption capacity for Ca²? ions, thereby creating a localized calcium-enriched microenvironment that significantly reduces the nucleation barrier for ettringite formation, leading to superior early hydration acceleration compared to calcite. Driven by thermodynamic metastability, vaterite demonstrates a notably higher reaction degree than calcite, enabling deeper participation in aluminate conversion, promoting monocarbonate formation, and stabilizing ettringite. This study elucidates the stability maintenance mechanism of vaterite in the CSA system, providing a robust theoretical foundation for the efficient utilization of vaterite mineralization products in low-carbon CSA cement.

Abstract:

To address the low immobilization efficiency of multiple heavy metals in municipal solid waste incineration fly ash (IFA), a fully resource-oriented technology that couples alkali pretreatment with sludge incineration residue (APCR)-based supersulfated cement (SSC) is proposed. The effects of alkali types and temperatures on the pozzolanic activity of IFA, as well as the performance, stabilization/solidification efficiency and mechanism of SSC, were investigated. Results show that Ca(OH)2 solution at 70?°C (CH70) eliminated the hydrogen production in IFA and significantly enhanced its pozzolanic activity. After incorporating into the SSC (M-CH70), the 28-days compressive strength reached 19.5 MPa, which was 12.2 times higher than that of the control group. Microscopic analysis confirms that the pretreated IFA provided abundant nucleation sites, promoted the interwoven growth of ettringite and C-(A)-S-H gels, and remarkably refined the pore structure of SSC. This SSC system exhibited excellent synergistic stabilization/solidification capability for heavy metals, Cl- and SO42-, with leaching concentrations far below the limited values specified in standards. This technology provides a new pathway for the low-carbon and high-value utilization of IFA.

Abstract:

Carbonated ready-mixed concrete serves as an effective approach to mitigate CO2 emissions in the cement and concrete industry. This paper systematically reveals the impact of CO2 mixing on the early hydration and phase evolution of fresh cement paste. The results demonstrate that CO2 mixing significantly accelerates the hydration process during the initial and induction periods, while exhibiting minimal effects on the heat release and microstructural build-up rate during the acceleration period. Meanwhile, CO2 mixing alters the early reaction pathway and phase assemblage of the paste, increasing the degree of cement reaction by 10.2%, accompanied by a reduction in CH and increases in CaCO3, amorphous phases, and chemical bound water, while promoting the formation of low-calcium C-S-H gel. In addition, CO2 mixing causes Ca2+ to preferentially participate in CaCO3 precipitation, thereby lowering the saturation indices of clinker minerals, gypsum, AFt, and CH, promoting the dissolution of clinker minerals and gypsum while inhibiting the precipitation of CH and AFt. Concurrently, low-calcium C-S-H and nano-CaCO3 advance the early microstructural build-up. These findings provide a theoretical basis for the engineering application of carbonated ready-mixed concrete.

Abstract:

To investigate the crack propagation and damage–fracture characteristics of dam concrete under complex hydraulic loading conditions, three-point bending tests with varying loading rates were conducted on fully graded concrete. Acoustic emission (AE) and digital image correlation (DIC) techniques were employed to monitor and evaluate the crack evolution and fracture damage process under different loading rates, and a rate-dependent fracture energy model was established.The results indicate that the peak load at concrete fracture is closely related to its axial tensile strength, which exhibits a significant strain-rate effect. As the loading rate increases in the later loading stage, AE activity becomes noticeably more pronounced. The strain-rate sensitivity coefficient of fully graded concrete under varying loading rates is determined to be 0.21. The proposed rate-dependent fracture energy model can reasonably characterize the strain-rate-sensitive behavior of fully graded concrete.Moreover, this model provides reliable parameter support for incorporating rate-dependent effects into constitutive models of concrete fracture behavior.

Abstract:

The long-term safe operation of nuclear facilities poses severe challenges to the performance stability of internal concrete structures exposed to prolonged neutron irradiation. This study aims to reveal the damage mechanisms of different neutron fluences on the macroscopic mechanical properties and microstructure of concrete under realistic irradiation conditions. The main conclusions are as follows. Mechanical test results show that the compressive strength gradually decreases with increasing neutron fluence. SEM observations indicate that, under relatively low neutron fluence, the number of pores increases in the cement paste and interfacial transition zone. Since the neutron fluence is lower than the threshold required to induce aggregate cracking, no obvious cracking of aggregates is observed, and the damage is mainly manifested as microstructural deterioration of the cement paste and interfaces. XRD results show that some crystalline peaks in the mortar gradually intensify with increasing cumulative neutron fluence, indicating changes in the phase composition of the mortar. This phenomenon may be related to long-term irradiation-induced heating, moisture migration during service, and water loss from the cement paste.

Abstract:

To elucidate the transport mechanism of chloride ions (Cl?) in concrete under multi-ion coupled environments, four immersion solutions—NaCl, composite salts (NaCl+Na?SO?, NaCl+MgSO?), and simulated seawater (SW-4)—were employed to investigate Cl? transport behavior in mortar. Chloride ion concentrations were measured at four ages ranging from 60 to 150 days, while the phase composition, microstructure, thermogravimetric characteristics, and pore structure were analyzed using XRD, SEM, TGA, and MIP. The results indicate that the ionic species present in the immersion solution play a decisive role in chloride transport. At early ages, SO?²? reacts with AFm phases to form ettringite, which fills pores and inhibits Cl? diffusion while simultaneously weakening the chemical chloride-binding capacity of the fly ash-slag system; at later ages, the expansive crystallization of ettringite induces microcracking and accelerates Cl? penetration. Mg²? initially forms Mg(OH)? precipitates that temporarily retard chloride diffusion, but subsequently decomposes C-S-H gel, leading to microstructural deterioration and accelerated Cl? migration. In simulated seawater, the relatively low concentrations of SO?²? and Mg²? result in a weaker synergistic effect, though its long-term impact cannot be overlooked.

Abstract:

The application code system of the National Natural Science Foundation of China (NSFC) serves as the institutional cornerstone of the Foundation’s funding framework. Its scientific rigor and forward-looking design directly influence the development of research disciplines and the effectiveness of funding allocation. In 2025, the Division of Architecture and Civil Engineering undertook a systematic review, optimization, and restructuring of its research areas and keyword system. Specifically, “E0805 Engineering Materials” was expanded from its original 8 research areas to 32, accompanied by a comprehensive refinement of its keyword system. This revision marked a fundamental transition from a relatively fragmented structure toward a more systematic, comprehensive, and globally integrated framework. Guided by the principles of vertical deepening, horizontal expansion, and application-oriented extension, this revision substantially redefined both the scope and the intellectual coverage of the discipline. This report systematically elucidates the overall framework, logic, and strategic considerations behind the optimization of the research areas and keyword system, while also providing analysis and interpretation of future development trends and strategic priorities.

Abstract:

Through systematic experiments, the freeze-thaw resistance of repair mortars with different mix proportions made from coastal restoration materials such as sea sand, mineral powder, and machine-made sand was analyzed and compared with traditional ancient city wall repair mortars. To predict the freeze-thaw resistance index of coastal ancient city wall repair mortars under freeze-thaw conditions, a stacking ensemble learning hybrid model combining a BP neural network, optimal single model (XGBoost), and support vector machine (SVM) was proposed. By training and validating 60 sets of freeze-thaw test data, this model addresses the shortcomings of single models, such as local optima, overfitting, and insufficient generalization ability. The root mean square error (RMSE) and mean absolute error (MAE) of the ensemble learning hybrid model are 6.8 and 5.2, respectively, which are reduced by 17% and 20% compared to XGBoost; for samples with high cycle counts, the prediction error is controlled within 3.2, and the robustness is significantly better than that of single models.

Abstract:

To investigate the effect of membrane thickness on the shear behavior of the polymer-cement interface, direct shear tests were conducted under different membrane thicknesses (1 mm, 3 mm, and 5 mm) and normal stresses (0.1–0.3 MPa). The shear response characteristics and failure mode evolution were systematically analyzed. The results indicate that the interfacial shear strength increases approximately linearly with normal stress. Increasing membrane thickness leads to a reduction in interfacial load-bearing capacity while significantly enhancing deformation capacity. Meanwhile, the failure mode gradually transforms from interfacial debonding to mixed failure. A semi-empirical damage model incorporating the membrane thickness effect was established, and it was shown to reasonably reproduce the nonlinear evolution of the interfacial shear stress-displacement response within the investigated range of test conditions. The findings reveal the coupled effects of membrane thickness and normal stress from both mechanical and modeling perspectives, and provide a reference for the design of sprayed waterproofing systems.

Abstract:

To investigate the toughness enhancement mechanisms of steel fibers in recycled aggregate concrete, 27 groups of specimens were designed with steel fiber volume fraction, concrete strength grade, and aggregate type as experimental parameters. A series of cube compressive, splitting tensile, and uniaxial tensile tests were conducted. The effects of the test parameters on compressive strength, splitting tensile strength, and uniaxial tensile stress?strain relationships were analyzed. Combined with cross-sectional steel fiber distribution, the steel fiber enhancement mechanisms for uniaxial tensile performance of recycled aggregate concrete were revealed. A uniaxial tensile constitutive model for steel fiber-reinforced recycled aggregate concrete was established. The results demonstrate that the incorporation of steel fibers effectively suppresses crack propagation, shifting the failure mode from brittle to ductile. With increasing steel fiber volume fraction, splitting tensile strength, uniaxial tensile strength and toughness are significantly enhanced. However, an excessively high volume fraction leads to fiber clumping, which reduces the efficiency of toughness enhancement. It is recommended that the steel fiber volume fraction in recycled aggregate concrete below C60 strength grade be limited to 1.5%.

Abstract:

Red mud is a highly alkaline industrial solid waste, and its utilization in alkali-activated cementitious materials represents an important resource recovery pathway. However, the activation effects of different activators and the optimal red mud dosage remain insufficiently studied. This paper focuses on activator screening, comparing the effects of four activators—water glass, lime, sodium hydroxide, and cement—on the performance of red mud-based cementitious materials at varying red mud dosages (15%–55%). The results show that the highly alkaline environment provided by water glass effectively activates the pozzolanic activity of red mud and slag, generating substantial amounts of C,N-A-S-H gel. The SO?²? from phosphogypsum promotes the precipitation of an appropriate amount of needle-like AFt crystals. When the mass ratio of red mud, slag, phosphogypsum, and water glass is 45%:40%:10%:5%, the hydration is most complete, achieving a 28-day compressive strength of 44.1 MPa. At this ratio, the gel phase interweaves with AFt to form a dense three-dimensional network structure, significantly enhancing strength. Furthermore, the carbon emission coefficient of this mixture is only 1.89 kg CO?/MPa, approximately 79% lower than that of traditional cement. Meanwhile, all pollutant indicators of the red mud-based cementitious material meet the requirements of the GB 8978—1996 Integrated Wastewater Discharge Standard. These findings demonstrate significant low-carbon advantages and engineering application potential.

Abstract:

To evaluate the long-term durability of basalt fiber-reinforced polymer (BFRP) composites under the harsh environment of cold and arid regions in Northwest China, accelerated aging tests under the coupled action of ultraviolet (UV) radiation and acid rain were carried out in accordance with the typical climatic characteristics of the region. By comparing with the single-environment test data obtained in previous studies by the research group, the degradation of macroscopic mechanical properties and the evolution of microscopic damage of BFRP were systematically investigated. The results show that there is a significant synergistic effect of UV radiation and acid rain on the deterioration of BFRP, and the attenuation degrees of tensile strength, elastic modulus and elongation at break are much greater than the superposition of those under single environmental exposure. Microscopic analyses (SEM/EDS) reveal the mechanism of the synergistic effect: UV radiation embrittles the resin matrix and generates microcracks, which provide pathways for acid solution penetration; acid rain further erodes the fibers and the fiber-matrix interface along these cracks, form a coupled damage cycle of "physical channeling followed by chemical penetration", which accelerates material failure. Based on the grey system theory, a GM(1,1) prediction model was established with excellent fitting accuracy, and the average relative accuracy is better than 5%, which is suitable for long-term performance prediction with small sample sizes. The research results can provide theoretical and data support for the durability design, safety evaluation and service life prediction of BFRP used in outdoor engineering structures such as photovoltaic supports in Northwest China.

Abstract:

To meet the set-on-demand requirements of concrete for digital fabrication, a helical static mixer has been employed for inline mixing of two reactive constituent streams immediately before extrusion. This paper focuses on optimizing the geometric design of the static mixer to enhance mixing efficiency using computational fluid dynamics (CFD). Two key design parameters were investigated, including the twist angle of the mixing elements and the contact angle between adjacent elements. Tracer particles were introduced into the two inlet streams to visualize the flow pattern inside the static mixer. In addition, the pressure drop across the static mixer was evaluated to assess energy efficiency. Simulation results indicate that a twist angle of 180° and a contact angle of 90° offer the most favorable configuration for striation formation and reduced resistance in digital concrete applications.

Abstract:

An environmentally friendly preparation strategy for layered magnesium oxide has been successfully applied in ABS resin flame-retardant systems, enabling the substitution of high concentrations of antimony trioxide. Layered magnesium oxide (MMH) was prepared via calcination to tailor its structure and phase composition, and was compounded with bromine-antimony systems to prepare flame-retardant ABS composites. Characterization results revealed that MMH possessed a high specific surface area with nano- pore structures. When MMH replaced 45% of antimony trioxide, compared to ABS (ABS/13.2TBPC/4.4Sb2O3), the limiting oxygen index (LOI) of ABS4 (ABS/13.2TBPC/2.4Sb2O3/2.0MMH) increased from 26.6% to 27.4%, and achieved V-0 grade in UL-94 testing as well as the reduction in peak heat release rate. Meanwhile, the introduction of MMH enhanced the tensile and flexural strength of ABS composites. Flame retardant mechanism indicated that MMH achieved efficient substitution of antimony trioxide by promoting the formation of the dense, protective charring layers, accompanied by synergistic flame inhibition in the gas phase. The preparation of layered magnesium oxide provides a new approach for developing an efficient and environmentally friendly ABS flame-retardant system.

Abstract:

Cyclodextrin (CD) is the main functional composition of the concrete temperature rising inhibitor. The influence of CD on the formation process of two main hydrates of Portland cement, Ca(OH)2 and C-S-H gel was studied to understand in-deeply the suppression mechanism of CD on the hydration of Portland cement and how to decrease its exothermic rate in early age of hydration. It is also studied how the hydration of C3S shielded from CD is intervened by the hydration of C3A. Two main hydrates of Portland cement, Ca(OH)2 and C-S-H gel, were synthesized using coprecipitation in a base solution containing different concentration of CD. Ca and Si concentration, total organic carbon content, conductivity and pH value of solution were measured during the synthesizing process. The time-depended variation of Ca/Si ratio of C-S-H gel was determined based on the EDS data. An isothermal calorimetric measurement was done on the hydration of C3S shielded from CD and intervened by the hydration of C3A. The degree of supersaturation of Ca(OH)2 precipitation is enhanced and the beginning of Ca(OH)2 precipitation is delayed with the addition of a little CD. The degree of supersaturation of C-S-H is also enhanced by the addition of CD. It increases the difficulty of C-S-H precipitation. The higher the dosage of CD, the higher the supersaturation of hydrates related to solution is, the more difficult the formation of Ca(OH)2 and C-S-H gel are. C-S-H gel with high Ca/Si ratio is formed in the early hydration period, then changes to one with low Ca/Si ratio. The dosage of CD does not alter the final Ca/Si ratio of C-S-H gel. CD can enhance the hydration of C3A, increases the concentration of aluminate in solution. It suppresses the hydration of C3S. It is the principal route that CD decreases the exothermic rate of Portland cement in its main hydration period. The second route is that CD adsorbed on C-S-H gel hinders the growth of C-S-H gel.

Abstract:

3D printed concrete relies on high?yield?stress material deposition, making traditional vibration difficult to apply because it significantly reduces the yield stress and disrupts the stability of the layered structure. This leads to poor pore structure, which limits the optimization of mechanical properties and durability. To address this problem, this study proposes a synergistic densification method combining ultrasonic vibration and nano?SiO?. A 3D printing nozzle with integrated ultrasonic vibration was developed to achieve multi?scale pore structure modification through ultrasonic cavitation effects along with micro?filling and chemical reactions from the nanoparticles. Experiments were conducted on a control group (CN), an ultrasonic?only group (UY0), and synergistic groups with varying nano?SiO? contents (UY5?~?UY20). Macro?performance and micro?structure were tested. The results show that the synergistic action promotes the formation of a dense clustered C?S?H gel network, significantly refining the pore structure and morphology. The UY15 group (with 0.15% nano?SiO?) exhibited the best overall performance: density increased by 15.9%, water absorption coefficient decreased by 56.5%, compressive and flexural strengths improved by 30.2% and 11.4% respectively, and the impermeability grade reached P8. This research provides an effective solution for pore structure control and performance enhancement of 3D printed concrete.

Abstract:

As an integral part of building facades, crack damage would appear in stone cladding due to chemical, physical, and extreme hazards. It is difficult to perform real-time identification and measurement of these crack damages with traditional instrumentations. In this study, an integrated software and hardware system is developed using artificial intelligence algorithms, graphics processing unit (GPU), and binocular camera. A group of damage images is built according to respective damage levels. Transfer learning, deep splitable convolution module, and dense block were implemented in the U-Net, and therefore the crack damage is conveniently segmented in the system. The crack measurement software is developed and implemented with Intel RealSense camera and GPU. The precision and recall of the developed novel system are both in ideal performance. The output of the platform is the damage level and geometry of the crack damage. This work can be applied in defect evaluation of the building envelope system, and beneficial to the structural safety detection and evaluation of various infrastructures.

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 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 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 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:

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:

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:

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:

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:

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:

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:

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:

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.