Table of Content

Volume 45 Issue 9
15 September 2026

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Cement and Concrete

Research Progress on Crystal Form Modification of Ye’elimite and Its Effect on Hydration Process

XU Mingfeng, WANG Lancheng, NIE Song, ZHOU Jian, LI Hui, PI Zhenyu

2026, 45(9):  2967-2983.  doi:10.16552/j.cnki.issn1001-1625.2026.0262

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Ye’elimite （C₄A₃S） is the principal clinker mineral in sulfoaluminate cement， characterized by low carbon emissions and high early-age reactivity. C₄A₃S exists in three polymorphic forms： cubic， orthorhombic， and tetragonal systems， which exhibit distinct hydration activities. Therefore， elucidating the relationship between crystal structure and hydration activity of C₄A₃S and achieving effective regulation of its crystal form are of great significance for developing novel sulfoaluminate cement clinker systems. This paper systematically reviews the crystal form regulation methods of C₄A₃S， including temperature control method， molten salt synthesis method， and ion doping method， with emphasis on analyzing the efficacy and underlying mechanisms of different regulation methods. On this basis， combined with the structural characteristics of various C₄A₃S crystal form， the influence of crystal form regulation on hydration kinetics， hydration activity， and hydration products is summarized and analyzed， providing theoretical references for the application of C₄A₃S crystal form regulation technology in sulfoaluminate cement.

Properties of Acrylamide-Modified Calcium Aluminate Cement-Based Materials and Their Hardened Mudstone

ZHANG Fengshun, CHAI Hucheng, SONG Mingjiang, GUO Jiajun, ZHANG Haibo

2026, 45(9):  2984-2998.  doi:10.16552/j.cnki.issn1001-1625.2026.0253

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The rapid argillization of floor mudstone in coal mine roadways under the erosion of geological water and construction water severely affects roadway driving efficiency and personnel safety. The current main treatment process involves first removing the softened mudstone and then pouring concrete； however， this process suffers from long hardening cycles， high construction intensity， and significant occupation of transportation resources. In this study， an acrylamide （AM）-modified calcium aluminate cement-based material was developed to achieve rapid hardening of argillized floors and enhance water erosion resistance. The setting and hardening times， central reaction temperature， and mechanical properties of the calcium aluminate cement-based material （composed of calcium aluminate cement， ordinary Portland cement， and gypsum at a mass ratio of 5∶1∶4） were tested at different AM dosages （0%， 5%， 10%， 15%， 20%， and 30% by mass of the cementitious material）. The modification mechanism was explored through microstructural analysis. Furthermore， the mudstone hardening performance was investigated using the calcium aluminate cement-based material that exhibited the best modification effect. The results show that a high AM dosage shortens the setting time of the calcium aluminate cement-based material and improves its flexural strength， deformability， and compressive failure absorbed energy. At an AM dosage of 20% （mass fraction）， the modified calcium aluminate cement-based material has initial and final setting times of 48 and 64 min， respectively， which are reduced by 44.8% and 35.4% compared with the AM-free group. At 28 d of curing， its flexural strength， compressive failure strain， and compressive failure absorbed energy are 9.7 MPa， 22.7%， and 636.1 J·m^-3， respectively， representing increases of 115.6%， 808.0%， and 1 833.4% over the unmodified material. The mudstone specimens hardened with the AM-modified material exhibit better water erosion resistance， with the loss rates of flexural strength and compressive strength being 3.1% and 3.8%， respectively， under immersion conditions. Microstructural analysis reveals that AM polymerizes in the cement matrix to form polyacrylamide， which interpenetrates with hydration products such as ettringite， constructing a flexible-rigid dual network structure. This structure improves the flexural strength of the calcium aluminate cement-based material and imparts a ductile fracture mode. Under a water erosion environment， the polyacrylamide adsorbed on the mudstone surface in the AM-modified hardened mudstone specimens absorbs water preferentially over the mudstone components. By reducing the swelling and disintegration of mudstone components under immersion and optimizing the pore structure， the water erosion resistance of the hardened mudstone is improved. This study provides a high-performance material for the rapid hardening of argillized floor mudstone in coal mine roadways， which is of great significance for ensuring the stability and safety of these roadways.

Water Dispersion Resistance of Sodium Polyacrylate Modified Magnesium Phosphate Cement-Based Grouting Material

YANG Weihui, LIU Guoshun, LI Yue, HUANG Dong, HUANG Chaoqun, LIU Yunpeng

2026, 45(9):  2999-3009.  doi:10.16552/j.cnki.issn1001-1625.2026.0241

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Leakage under flowing water is a challenge issue in underground engineering. Grouting materials must remain injectable before reaching the target zone and set rapidly after placement to resist washout. Magnesium phosphate cement （MPC） offers fast setting， high early strength and good bonding， making it promising for dynamic water sealing. However， MPC suffers from severe dilution and washout under the high water-to-solid ratio required for two-component grouting.

This study aims to improve the anti-washout performance of MPC grouting materials by incorporating two thickening components into the MgO slurry and the ammonium dihydrogen phosphate （ADP） solution， respectively. The combined effects of hydroxypropyl methylcellulose （HPMC） and sodium polyacrylate （PAAS） on the workability， rheology， mechanical properties， and water dispersion resistance of MPC were systematically investigated. The anti-washout mechanism was further explored via X-ray diffraction （XRD）， thermogravimetric analysis （TG-DTG）， scanning electron microscopy （SEM）， conductivity measurement， and pH analysis.

The results show that HPMC （0.2% by mass of MgO） can form a stable spatial network structure in the MgO slurry， effectively reducing bleeding to nearly 0% and improving suspension stability. However， when mixed with the phosphate solution， the HPMC network collapses due to the salting-out effect caused by the high ionic strength environment （Mg²⁺， NH{}_{\mathrm{4}}^{+}， H₂PO{}_{\mathrm{4}}^{-}）， leading to negligible improvement in anti-washout performance. In contrast， PAAS （0.2% to 1.1% by total mass of ADP and borax） can form a stable three-dimensional network in the presence of borax， which acts as a crosslinking agent. Even under high ionic strength， the PAAS network remains intact， significantly increasing the yield stress and consistency coefficient of the MPC slurry. The Herschel-Bulkley rheological model fitting results show that with increasing PAAS content， the yield stress （τ₀） increases from 36.18 MPa to 943.20 MPa， and the consistency coefficient （k） increases from 1.63×10^-3 to 60.81×10^-3， indicating a strong shear-thickening behavior （n>1）.

The optimal formulation is achieved with 0.2% HPMC in the MgO slurry and 0.8% PAAS in the phosphate solution （P-0.8 group）. Under a water flow velocity of 0.8 m/s， the grout retention ratio reaches 0.88， and the 3 d water-to-land strength ratio exceeds 0.9. Compared to the unmodified group （P-0）， the compressive strength at 28 d increases slightly from 3.60 MPa to 3.71 MPa. In contrast， the HPMC-modified group （H-0.8） shows significantly lower strength （2.64 MPa at 28 d） due to the introduction of micro-air bubbles and network collapse. XRD and TG-DTG analyses confirm that PAAS does not alter the hydration products （mainly MgO and struvite）， but promotes struvite formation slightly. SEM observations of freeze-dried hydrogels further reveal that borax crosslinking enables PAAS to maintain an intact porous network even in the presence of ADP， effectively resisting the salting-out effect.

In conclusion， PAAS is more suitable than HPMC for modifying MPC grouting materials in dynamic water environments due to its superior structural stability under high ionic strength. Borax plays a dual role as a retarder and a crosslinking agent， enhancing the network stability of PAAS. This study provides a new technical approach for applying MPC in dynamic water sealing of underground engineering， with tunable anti-washout performance by adjusting PAAS dosage.

Influence Mechanism of Nano C-S-H on Cement Hydration and Mortar Properties

HU Min, ZHANG Han, CHENG Huijuan

2026, 45(9):  3010-3016.  doi:10.16552/j.cnki.issn1001-1625.2026.0400

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To clarify the influence of nano calcium silicate hydrate （C-S-H） on cement hydration and mortar properties， this paper investigated the effect of 0% to 5% （mass fraction） nano C-S-H on the compressive strength， flexural strength， setting time， and other performance indicators of cement mortar. The microscopic mechanisms were revealed through X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicate that nano C-S-H can effectively promote the cement hydration process and improve early strength. With the increase of nano C-S-H dosage， the compressive strength and flexural strength of cement initially increase and then decrease. When the nano C-S-H dosage is 3%， both compressive strength and flexural strength are significantly improved. When the nano C-S-H dosage is 4%， the compressive strength and flexural strength reach their peak， with an increase of 11.4% and 18.1%， respectively， compared to the control group after 28 d of curing. As the nano C-S-H dosage increases， the initial setting time and final setting time of cement continue to shorten， and the shrinkage rate gradually increases. At a 5% dosage， the shrinkage rate increases by 22.7% compared to the control group. When the nano C-S-H dosages is 0% to 3%， the initial fluidity increases with the increase of nano C-S-H dosage. When the nano C-S-H dosage exceeds 3%， the initial fluidity decreases with the increase of nano C-S-H dosage. Microscopically， nano C-S-H can effectively promote the hydration of di-calcium silicate （C₂S） and tri-calcium silicate （C₃S） in cement. With the increase of nano C-S-H dosage， the production of flocculent hydration product C-S-H gel gradually increases， making the interior of specimen denser and effectively improving the early compressive strength of cement mortar. However， as the curing time increases， the effect of nano C-S-H on strength gradually decreases. The research results can provide a reference for the application of nano C-S-H in cement-based composite material.

Shrinkage Performance and Micro-Pore Structure of Sisal Fiber-Reinforced Cement Mortar under Low Atmospheric Pressure Environment

SUN Binqiang, TIAN Maosheng, ZHENG Lei, XIE Chao, DAI Jinpeng, XIE Dengkui

2026, 45(9):  3017-3026.  doi:10.16552/j.cnki.issn1001-1625.2026.0183

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To investigate the shrinkage performance and micro-pore structure evolution of sisal fiber-reinforced cement mortar under plateau low atmospheric pressure environments， this study simulated two curing pressure conditions： 57.6 and 95.0 kPa. Cement mortar specimens reinforced with sisal fibers of varying lengths （5， 10， 15， and 20 mm） were prepared. The shrinkage performance， splitting tensile strength， micro-pore structure， and fracture surface morphology were systematically evaluated.The results indicate that reducing the curing environment atmospheric pressure significantly increases the shrinkage rate， reduces the splitting tensile strength， and deteriorates the micro-pore structure of all specimen groups. Compared to the 95.0 kPa atmospheric pressure environment， specimens cured at 57.6 kPa exhibit 5.9% to 13.1% increase in shrinkage rate， 8.3% to 10.9% decrease in splitting tensile strength， and 14.9% to 21.9% increase in porosity， accompanied by pore coarsening. The incorporation of sisal fibers effectively inhibits the shrinkage of cement mortar and enhances its splitting tensile strength. Compared to plain mortar， the shrinkage rates of sisal fiber-reinforced cement mortar specimens decrease by 5.3% to 15.3% and 3.0% to 9.5% under 57.6 and 95.0 kPa， respectively. Meanwhile， the splitting tensile strength increases by 8.8% to 29.4% and 7.9% to 26.3%， respectively. Furthermore， the 10 mm sisal fibers demonstrate the optimal effect in inhibiting shrinkage and enhancing matrix strength， attributed to their excellent dispersion within the matrix and efficient stress transfer capability.

Performance and Microstructure Evolution of Sulfate-Resistant Double-Liquid Grouting Material for Shield Tunnel

ZOU Yingjie, LI Huajian, HUANG Fali, FENG Junjie, SHI Henan, DONG Haoliang, YI Zhonglai

2026, 45(9):  3027-3042.  doi:10.16552/j.cnki.issn1001-1625.2026.0280

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In order to deal with the erosion of sulfate in groundwater to the grouting material of shield tunnel， a sulfate-resistant double-liquid grouting material was developed. The effects of water-binder ratio （w/b）， ground granulated blast furnace slag （GGBS） content and liquid volume ratio of A and B （liquid A is cementitious material slurry， liquid B is sodium silicate solution） on the working performance， mechanical properties and sulfate resistance of double-liquid grouting materials were studied. The mechanism of sulfate resistance improvement was revealed by XRD， SEM-EDS， TG-DTG and FTIR. The results show that the grouting material has good fluidity， the 28 d compressive strength is 9.38 MPa to 17.17 MPa， and the corrosion resistance coefficient is more than 0.8. It has excellent mechanical properties and sulfate resistance while meeting the requirements of construction fluidity. The content of GGBS has the most significant effect on the compressive strength and corrosion resistance coefficient of grouting materials. The reason is that GGBS exerts filler effect and pozzolanic activity to consume Ca（OH）₂ to form more C-S-H gel， which promotes the formation of dense microstructure and improves mechanical properties. Reducing w/b and increasing GGBS content can promote the formation of physical barrier to block the migration and diffusion of external SO{}_{\mathrm{4}}^{\mathrm{2}-}， and promote the effective adsorption of SO{}_{\mathrm{4}}^{\mathrm{2}-} by C-S-H， thereby improving the sulfate resistance of grouting material.

Numerical Simulation on Chloride Ion Transport in Concrete under Freeze-Thaw Cycles by Considering Multi-Field Coupling

LI Kai, GAO Changtian, SHI Caijun

2026, 45(9):  3043-3054.  doi:10.16552/j.cnki.issn1001-1625.2026.0279

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Concrete in service is often subjected to various harsh environments， including freeze-thaw cycles， alternate wetting and drying and chloride ion corrosion. Consequently， the issues of chloride salt erosion in concrete gradually become prominent and attract a lot of attention in recent years， since it acts as a serious threaten to the service life of concrete materials. Once freeze-thaw cycles happen， a periodic variation in the temperature does not only induce the transition of water into ice， but also results in a damaged pore structure and occurred water convection phenomenon. On one hand， the changes in temperature can directly affect the diffusion rate of chloride ion. On the other hand， the pore ice would block the transport channels of chloride ion， while the water convection effect induced by pore pressure and cryosuction pressure could promote the movement of chloride ion as well. Moreover， the aggregates of arbitrary shape in concrete also have a significant influence on the transport of chloride ion. Unfortunately， existing studies often simply treat concrete as a homogeneous material， and its actual shape on chloride ion transport is just ignored. Hence， in order to reveal the mechanism of chloride ion transport in concrete under multi-field coupling effects during freeze-thaw cycles， the morphological characteristics of real aggregates and multi-field coupling effects during freeze-thaw cycles should be all taken into account.In this work， a three-phase concrete model at meso-scale was first built in which irregular aggregate packing structure was carefully considered. A multiphysics numerical simulation method was then employed to study the chloride transport process in concrete under different conditions. The model’s accuracy and applicability were compared to experimental results and a good agreement was observed in case the gradient distributions of temperature and pore ice content during freeze-thaw cycles， along with the water convection effect were taken into account. Afterwards， the influences of the number of freeze-thaw cycles， temperature range， freeze-thaw time ratio and salt solution concentration on the behavior of chloride ion transport were further investigated.The results show a damaged pore structure caused by freeze-thaw effect after 100 cycles enables the specimen’s chloride ion diffusion coefficient to be enlarged by 34.40 times. In case the water convection effect is neglected， the obtained chloride transport depth and average concentration in concrete are reduced by 5 mm and 1.16 times， respectively. Meanwhile， a wider temperature range and a higher freeze-thaw time ratio contribute to an increased temperature gradient inside concrete during thawing， thereby enhancing water flow velocity， but the latter can also diminish the blocking effect of pore ice on transport path， so the chloride ion transport process is still facilitated. Although an increase in salt solution concentration would weaken the water convection effect， the chloride concentration gradient is raised and the formation of pore ice is inhibited， resulting in an elevated chloride ion transport rate.

Interpretable AI-Driven Design of Economically Low-Carbon Ultra-High Performance Concrete Mix Proportion

HUANG Xin, CHEN Xin, SHENG Jialin, WANG Junbo, YUAN Jie

2026, 45(9):  3055-3069.  doi:10.16552/j.cnki.issn1001-1625.2026.0315

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Ultra-high performance concrete （UHPC） demonstrates immense potential for enhancing structural load-bearing capacity and service life. However， UHPC mix proportion design involves highly nonlinear couplings among multiple components and parameters. Conventional trial-and-error methods are constrained by long experimental cycles， high costs， and a single objective， making it difficult to achieve a systematic balance among mechanical properties， economic cost， and carbon emissions. In recent years， machine learning （ML） methods have been widely applied to performance prediction and mix proportion design of UHPC. Nevertheless， existing studies have yet to establish a systematic design framework that integrates high-quality data management， accurate interpretable prediction， and multi-objective collaborative decision-making.A UHPC mechanical property database was constructed based on an extensive review of published literature， comprising 17 input features and 2 output features. Optimal input dimensionality was determined through an embedded feature engineering method. A dynamic-weight stacking ensemble model （DW-Stacking） was developed using Random Forest （RF）， XGBoost （XGB）， CatBoost （CB）， and LightGBM （LGB） as base learners， incorporating a prediction error-based dynamic weighting and cross-fold smoothing mechanism. Three hyperparameter optimization strategies， namely Adaptive Grid Search （AGS）， Bayesian Optimization （BO）， and Enhanced Grey Wolf Optimization （EGWO）， were tested. The BO was selected for the final base learner optimization. SHAP analysis was further employed to quantify the contribution and directional influence of each input feature on UHPC mechanical properties. For multi-objective optimization， flexural strength， compressive strength， unit cost， and CO₂ emissions were defined as four parallel optimization objectives. An improved NSGA-Ⅱ algorithm was constructed， incorporating Latin hypercube sampling， dynamic parameter regulation， and parallel search operators. An entropy-weight TOPSIS decision method was then applied to select optimal mix proportions from the resulting Pareto front. The optimization results were verified through actual testing.The DW-Stacking model achieves test-set R² values of 0.927 and 0.958 for flexural and compressive strength prediction， respectively. Compared with the BO-RF baseline， RMSE is reduced by 45.3% and 25.6%； compared with standard Stacking， further RMSE reductions of 36.2% and 17.3% are attained. These results demonstrate that the dynamic weighting and smoothing mechanism effectively suppresses noise introduced by lower-quality sub-models and substantially enhances prediction robustness. SHAP analysis identifies steel fiber content， curing age， and silica fume content as the important factors governing UHPC mechanical properties， all of which exhibit positive correlations with both flexural and compressive strengths. In the multi-objective optimization stage， the improved NSGA-Ⅱ achieves an 18.4% increase in the hypervolume indicator and approximately 281% faster convergence relative to the original algorithm， reflecting superior solution quality and search efficiency. Experimental validation confirms that within the mix proportion design range， where cost and carbon emissions reductions do no exceed 25%， prediction errors for both flexural and compressive strengths of UHPC are consistently controlled within ±9%. When the cost and carbon-emission reduction targets are extended to 50%， the content of key materials in the optimized mix proportions deviate substantially from the training data distribution. This result in prediction errors exceeding ±25% for both output features and revealing the boundary conditions of the model’s reliable predictive range.This research formulates an interpretable， AI-driven collaborative design framework for UHPC. The proposed DW-Stacking model achieves superior accuracy in predicting the mechanical properties of UHPC. SHAP analysis effectively elucidates the positive effects of steel fiber， curing age， and silica fume content. Furthermore， the improved NSGA-Ⅱ algorithm efficiently realizes the synergistic optimization of different conflicting objectives. Experimental results confirm that the model can reduce the unit cost and carbon footprint of UHPC by about 25% while meeting the minimum mechanical-property requirements specified for structural UHPC， providing a reliable scientific tool for engineering practice.

Full-Age Prediction and Interpretability Study of Concrete Compressive Strength Based on Machine Learning

LI Shuo, QIN Yanhui, LI Meng’en, MA Haoyuan, YIN Jinshuai, ZHENG Lulu, DENG Suwen

2026, 45(9):  3070-3082.  doi:10.16552/j.cnki.issn1001-1625.2026.0229

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To address the problems of a long testing period， high cost， and difficulty in achieving full-process monitoring in the traditional determination of concrete compressive strength， this study developed a full-age prediction model for concrete compressive strength based on 1 250 sets of test data using four learning algorithms， namely random forest （RF）， eXtreme Gradient Boosting （XGBoost）， light gradient boosting machine （LightGBM）， and categorical boosting （CatBoost）. Combined with SHapley Additive exPlanations （SHAP） interpretability analysis， the influencing mechanism of concrete strength was revealed. The results show that the CatBoost model exhibits the optimal comprehensive performance， with a coefficient of determination R² of 0.96， a root mean square error （RMSE） of 3.29 MPa， and a mean absolute error （MAE） of 2.25 MPa for the full dataset. It also maintains a stable predictive capability across all stages including the early age （≤7 d）， medium age （14 d to 28 d）， and late age （>28 d）. XGBoost achieves the best performance in the fly ash-free system （R²=0.98）， while CatBoost has the strongest adaptability in the ground granulated blast furnace slag-free system （R²=0.95）. SHAP analysis verifies the core effects of the water-binder ratio law and pozzolanic effect， identifies age， cement content， and water content as the key influencing factors， with the water content of 170 kg/m³ to 180 kg/m³ being the strength inflection point. This study can provide a scientific basis for the optimization of concrete mix proportion and on-site rapid quality assessment， and has important engineering application value.

Comparative Study on Anti-Erosion Enhancement Technologies of Lining Concrete for Mountain Tunnels in Saline Soil Environment

WAN Guijun, GUO Zheng, LIU Chang, MU Song, DAI Jinpeng, LIU Rongxin, YANG Jing, WANG Xudong

2026, 45(9):  3083-3091.  doi:10.16552/j.cnki.issn1001-1625.2026.0214

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In the construction of tunnel engineering in saline soil environments of western China， the service conditions and construction practices for lining concrete are complex， posing significant challenges to both construction safety and durability. To identify the applicable scenarios of anti-erosion enhancement technologies， this study comprehensively evaluated the effects of environmental corrosion-resistance admixture and erosion inhibitor on the air permeability coefficient， carbonation depth， water penetration depth， water absorption， rapid chloride migration coefficient， and electric flux of tunnel lining concrete. The results show that the environmental corrosion-resistance admixture refines the capillary pore structure of concrete， significantly reduces the water penetration depth and air permeability coefficient， and improves sulfate corrosion resistance. The erosion inhibitor reduces the hydrophilicity of concrete， markedly decreasing the 0.5 h water absorption rate （by approximately 57%）， while significantly enhancing sulfate erosion resistance under dry-wet cycling and semi-immersion conditions. Comparing the two anti-erosion enhancement technologies， the environmental corrosion-resistance admixture is superior in improving concrete compactness， making it suitable for enhancing resistance to medium permeation under external water pressure， gas pressure， or an electric field. The erosion inhibitor is superior in improving concrete hydrophobicity， making it suitable for enhancing resistance to ion erosion under capillary adsorption conditions such as dry-wet cycling or semi-immersion. Considering the different service conditions and performance requirements of mountain tunnel linings in saline soil environments， it is recommended to adopt corresponding concrete anti-erosion enhancement technologies.

Acoustic Emission Characteristics of Shear Failure of Rock-Filled Concrete Aggregate-Paste Interface under Various Freeze-Thaw Cycles

ZHANG Tianqi, WANG Anhai, ZHOU Zeyang, LUO Tao, LI Li, ZHANG Qi

2026, 45(9):  3092-3108.  doi:10.16552/j.cnki.issn1001-1625.2026.0252

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Under high-frequency freeze-thaw environment in cold regions， the large-scale interface （aggregate-paste interface） formed between rockfill and self-compacting concrete in rock-filled concrete （RFC） is more susceptible to freeze-thaw damage， and this damage directly affects the long-term performance of RFC structures. In this paper， the shear failure process of the aggregate-paste interface under different freeze-thaw cycles was monitored based on acoustic emission technology， the degradation law of interfacial shear strength was analyzed， the shear failure modes at different stages were clarified， and an interfacial damage model based on acoustic emission parameters was constructed. The results show that with the increase of freeze-thaw cycles， due to the alternating effect of sliding friction and static friction at the interface， the shear strength-shear displacement curve exhibits an up-and-down oscillation phenomenon after the secondary peak， and the shear displacement at which this phenomenon occurs is continuously increased； the peak shear strength， secondary peak shear strength， and residual shear strength of the aggregate-paste interface decrease to 0.72， 0.19， and 0.13 MPa， with reductions of 66.04%， 81.55%， and 86.32%， respectively； based on the cumulative ringing count， the shear failure process can be divided into four stages. With the increase of freeze-thaw cycles， the proportion of shear cracks in stages Ⅰ， Ⅱ， and Ⅲ decreases， while the proportion of shear cracks in stage Ⅳ increases from 66.9% to 78.7%. Under freeze-thaw action， the dominant failure mode of the aggregate-paste interface is shear failure， and the damage model constructed based on acoustic emission energy can well describe the interfacial damage evolution process. The research results can provide a theoretical reference for the long-term service performance evaluation of rock-filled concrete projects in cold regions.

Analysis of Axial Compression Damage and Acoustic Emission Characteristics of Fiber-Reinforced Concrete

DIAO Jialong, WANG Jiacheng, WANG Qiang, WANG Nan, YIN Guoan, ZHANG Wei

2026, 45(9):  3109-3116.  doi:10.16552/j.cnki.issn1001-1625.2026.0290

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In order to explore the influence of polypropylene imitation steel fiber and steel fiber hybrid fiber on the mechanical properties of concrete， plain concrete （NC）， polypropylene imitation steel fiber concrete （PFRC-0.5， PFRC-1） and hybrid fiber concrete （PSRC-1） were designed， and the mechanical properties and damage evolution law of concrete under axial compression were explored by uniaxial compression mechanical test combined with acoustic emission monitoring technology. The results show that the compressive strength of hybrid fiber concrete （PSRC-1） is 23.11% higher than that of plain concrete， and the toughness is significantly enhanced. The acoustic emission ring-down count has a good correlation with the stress-strain curve， which can effectively reflect the various stages of axial compression process of concrete， and can provide an acoustic emission characteristic reference for the damage monitoring and failure mechanism of fiber reinforced concrete. The global acoustic emission b-value of PSRC-1 specimen is the highest， which is 0.42 higher than that of plain concrete， indicating that the hybrid fiber has good energy dissipation ability. The incorporation of fiber promotes the failure mode to shear failure， and the acoustic emission signal is concentrated in the low frequency band （50 kHz to 100 kHz）.

Dynamic Mechanical Properties and Failure Mechanism of Headed Stud Connectors in Composite Beams under Impact Loading

FENG Junhao, HU Hao, YU Zhenpeng, DU Xiaoqing, ZHANG Yongping

2026, 45(9):  3117-3125.  doi:10.16552/j.cnki.issn1001-1625.2026.0268

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To reveal the dynamic mechanical response and failure mechanism of headed stud connectors in steel-concrete composite beams under extreme impact loading， this study conducted experimental investigations on their dynamic shear performance through a combination of static push-out tests and drop-weight impact tests. The impact force and displacement time-history curves of the specimens under different drop heights were systematically obtained， and the failure modes and evolution of dynamic shear bearing capacity were analyzed.The results show that the mechanical performance of the headed stud connectors under drop-weight impact loading exhibits clear drop-height dependence and strain-rate effects. The failure mode， peak impact force， and displacement response vary significantly with increasing input impact energy. Under low-energy impact， the headed stud connectors mainly remain in an elastic response stage. Under medium-energy impact， asymmetric failure occurs， characterized by brittle shear fracture of headed studs connectors on one side accompanied by local concrete crushing. Under high-energy impact， brittle shear fracture occurs in the headed studs connectors on both sides， leading to complete interface failure.With increasing drop height， both the peak impact force and residual displacement increase markedly， and the dynamic shear bearing capacity is 72% to 176% higher than the static bearing capacity. Based on the experimental results， the relationship between the dynamic increase factor （DIF） and strain rate is established. A DIF-based calculation method for the dynamic shear bearing capacity of headed stud connectors is then proposed and validated through comparison with classical bearing capacity models for headed stud connectors. This study can provide a reference for the design and safety assessment of shear connections in composite structures subjected to extreme actions such as impact and explosion.

Synthesis of Hyperbranched Admixture and Its Effect on Low Water-Cement Ratio Cement Paste

MAO Zhiyi, ZHU Yizhou, YANG Renhe, QIE Feifan, ZHANG Pengyu, SUN Qian, LIU Xiao

2026, 45(9):  3126-3139.  doi:10.16552/j.cnki.issn1001-1625.2026.0289

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In order to regulate the rheological properties of ultra-high performance concrete effectively， an admixture with hyperbranched topological structure was synthesized by pentaerythritol， acrylic acid， methyl acryloxy polyoxyethylene ether （HPEG） and ceric ammonium nitrate （CAN）. The effects of the types and molecular weights of the monomers， the ratio of pentaerythritol to the monomers， and the initiator system on the fluidity and viscosity of the cement paste were investigated. The results show that when the monomer used is HPEG with a molecular weight of 1 000 g/mol， the ratio of pentaerythritol to the monomer is 0.012 5∶1， and the initiator used is ammonium cerium nitrate，the synthesized hyperbranched admixture combined with the laboratory-synthesized comb-like polycarboxylic water-reducing admixture at dosages of 0.3%（mass fraction） and 0.7%（mass fraction） respectively， is added to the cement paste with a water-cement ratio of 0.18， the flowability is 200 mm and the viscosity is 1 637 mPa·s. The viscosity is 31.8% lower than that of the commercially available UHPC admixture， achieving optimal rheological properties. Microscopic characterization methods， such as gel permeation chromatography， Fourier transform infrared spectroscopy， hydrodynamic radius， Zeta potential， total organic carbon and rheological property tests， were used to analyze the mechanism. The results show that the hyperbranched topological structure admixture has a compact molecular structure， a rich distribution of terminal functional groups， a fast interfacial adsorption rate， and also exhibits excellent dispersion and viscosity reduction properties.

Solid Waste and Eco-Materials

Strength and Expansion Properties of Hydrated Lime-Solidified CFB Ash-Slag-Based Controlled Low-Strength Material

PENG Shuang, GAO Peng, ZHOU Mingkai, XUE Xiu, WANG Yuqiang, QIN Zhiqing

2026, 45(9):  3140-3150.  doi:10.16552/j.cnki.issn1001-1625.2026.0216

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Controlled low-strength material （CLSM） was prepared through the synergistic activation of hydrated lime and circulating fluidized bed fly ash and slag （CFB ash-slag）. To clarify the development behavior， influencing factors， and mechanism of expansion properties in hydrated lime-solidified CFB ash-slag-based CLSM， the effects of ash-slag ratio， hydrated lime content， and water dosage on the unconfined compressive strength and linear expansion rate of the hardened CLSM specimens were investigated. XRD， SEM， and thermogravimetric analyses were employed to characterize the reaction products and elucidate their mechanisms. The results show that， within the tested range， the 28 d unconfined compressive strength reaches a maximum of 7.7 MPa at an ash-slag ratio of 40∶60， while increasing the ash-slag ratio causes only a slight rise in the linear expansion rate. Hydrated lime content is identified as the most significant factor. In the range from 0% to 25%， both the unconfined compressive strength and linear expansion rate of the hardened CLSM specimens increase markedly with increasing hydrated lime content. When the hydrated lime content increases from 0% to 5%， the 28 d unconfined compressive strength increases from 0.7 MPa to 6.2 MPa， and the linear expansion rate increases from 0% to 1.0%，showing the most remarkable growth. Increasing the water dosage significantly reduces the linear expansion rate of the hardened CLSM specimens； when the water dosage increases from 590 kg/m³ to 650 kg/m³， the linear expansion rate decreases by 62.5%. Microstructural analysis indicates that the main hydration products formed in the hydrated lime-solidified CFB ash-slag system are ettringite （AFt）， calcium silicate hydrate （C-S-H） gel， and hydrated calcium silicate aluminate （C-A-S-H） gel. AFt is mainly generated at the early stage， whereas the gel phases continue to develop at later ages. An increase in water dosage leads to a looser structure and higher porosity， thereby weakening both the strength and expansion properties of the hardened CLSM specimens.

Mechanical Properties and Microscopic Characteristics of Lime-Fly Ash-Solidified Saline Soil

CHEN Fei, ZHAO Hongting, WU Xiaopeng, LI Xiaolin, WAMG Fei

2026, 45(9):  3151-3162.  doi:10.16552/j.cnki.issn1001-1625.2026.0212

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To investigate the mechanical properties of lime-fly ash-solidified saline soil in the Hangzhou Bay area， this study conducted unconfined compression tests and direct shear tests， the influences of salt content and curing age on the solidification effect of lime and fly ash were analyzed. Furthermore， the scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP） tests were employed to reveal the microstructural characteristics of lime-fly ash-solidified saline soil （lime-fly ash soil）. The results show that the unconfined compressive strength， tangent modulus， and strain energy density of saline soil all initially increase and then decrease with the rise of salt content. Therefore， it can be inferred that there exists an optimal salt content regarding the influence of salt content on the mechanical properties of saline soil. The mechanical properties of lime-fly ash soil are significantly improved after the incorporation of lime and fly ash. They generally increase with rising salt content and curing age， however， a salt content exceeding 1% （mass fraction） does not lead to a further significant enhancement of these properties. Based on the microscopic test results， it is found that lime and fly ash can effectively improve the pore structure characteristics of saline soil. The pore volume， median pore diameter， average pore diameter， porosity， and fractal dimension of lime-fly ash soil are all lower than those of saline soil， and the bulk density of soil increases from 1.41 g/cm³ to 1.47 g/cm³. These parameters provide a better understanding of the relationship between the microstructural characteristics and macroscopic mechanical properties of lime-fly ash soil. The research results can provide a scientific reference for the application of lime-fly ash soil in practical engineering in the Hangzhou Bay area.

Influences of Water Glass Parameters on Working Performance and Mechanical Properties of Alkali-Excited Geopolymers

ZHOU Huiyong, WANG Yanchao, GAO Hua, GUO Wei, FAN Taotao, SI Chundi, MA Xibao

2026, 45(9):  3163-3173.  doi:10.16552/j.cnki.issn1001-1625.2026.0190

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To investigate the influences of alkali activator parameters on the working performance and mechanical properties of geopolymers， the geopolymers were prepared using iron tailings sand， coal gangue powder， and blast furnace slag as raw materials， employing both solid water glass and liquid water glass as alkali activators. The effects of water glass types， modulus and Na₂O dosage on geopolymers setting time， flowability， compressive strength and flexural strength were analyzed. Additionally， SEM and XRD were conducted to reveal the strength development mechanism of water glass-excited geopolymers. The results indicate that as modulus of water glass increases， the setting time of both alkali-excited geopolymers extends. Liquid water glass-excited geopolymers exhibit a trend of initially increasing then decreasing flowability， compressive strength and flexural strength， with an optimum modulus of 1.6. Solid water glass-excited geopolymers show a decreasing trend in flowability， while compressive strength and flexural strength initially decreases then increases， with an optimum modulus of 0.6. As the Na₂O dosage increases， the setting time and flowability of the geopolymers decrease while both compressive and flexural strength increase. The geopolymers exhibits optimal performance when the Na₂O content is 6% （mass fraction）. Liquid water glass-excited geopolymers exhibit superior working performance and mechanical properties compared to solid water glass-excited geopolymers. Both solid and liquid water glass are employed to modulate geopolymer strength development by influencing the geopolymerization reaction kinetics. Notably， solid water glass exhibits a relatively low dissolution rate in the alkaline activation medium， resulting in heterogeneous distribution of reaction products and consequently impeding uniform strength gain.

Optimization Design and Sulfate Resistance Performance of Multi-Source Solid Waste-Based Geopolymer Concrete

KONG Linghai, LIANG Genfu, HUANG Ye, HE Xunlin, ZHANG Benben, LUO Zhengdong

2026, 45(9):  3174-3186.  doi:10.16552/j.cnki.issn1001-1625.2026.0324

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To address the problems of high carbon emissions and insufficient durability of ordinary Portland cement concrete in sulfate-rich environments， this study used slag， fly ash and steel slag as composite precursors to prepare multi-source solid waste-based geopolymer concrete. Through orthogonal tests combined with grey relational analysis for auxiliary evaluation， the influences of steel slag dosage， alkali activator modulus， alkali activator dosage and external water-to-binder ratio on the compressive strength of geopolymer concrete were investigated， and the optimal mix proportion was determined. On this basis， sulfate wet-dry cycling tests were carried out， and combined with mass change， compressive strength corrosion resistance coefficient， X-ray diffraction （XRD） and scanning electron microscopy （SEM）， the sulfate resistance performance and damage mechanism of the multi-source solid waste-based geopolymer concrete were analyzed. The results show that the influence degree of the factors on the compressive strength of geopolymer concrete， in descending order， is alkali activator modulus， alkali activator dosage， external water-to-binder ratio， steel slag dosage. The optimal mix proportion is steel slag dosage of 20% （mass fraction）， alkali activator modulus of 1.2， alkali activator dosage of 50% （mass fraction）， and external water-to-binder ratio of 0.40. After 150 sulfate wet-dry cycles， the compressive strength corrosion resistance coefficient of the multi-source solid waste-based geopolymer concrete reaches 80%， which is higher than that of ordinary Portland cement concrete， and the mass change rate is only -0.6%. Microstructural analysis shows that the deterioration of ordinary Portland cement concrete is mainly related to the formation of expansive products such as gypsum and ettringite， and their continuous accumulation leads to the initiation and propagation of internal microcracks and structural spalling. In contrast， no obvious identifiable characteristic peaks of gypsum or ettringite are observed in the multi-source solid waste-based geopolymer concrete， and its damage is mainly manifested as local microcracks induced by sodium sulfate crystallization and slight loosening of the interfacial zone， without forming rapid deterioration dominated by the accumulation of a large amount of expansive sulfate products. The research results can provide a reference for the engineering application of multi-source solid waste-based geopolymer concrete in sulfate erosion environments.

Synthesis of High-Performance Cement Materials Using CaSO₄ Prepared from Phosphogypsum

CHEN Yiheng, FANG Keneng, CHEN Qianlin

2026, 45(9):  3187-3201.  doi:10.16552/j.cnki.issn1001-1625.2026.0196

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To improve the resource utilization rate of phosphogypsum （PG）， in this study， anhydrous gypsum （AH） prepared by the PG crystallization method， hemihydrate gypsum （HPG） prepared by calcining PG， calcium sulfoaluminate （CAS）， and calcium oxide （CaO） were used to develop a sustainable， fast-setting， high-strength cementitious material （AHCSO） based on PG. The results indicate that the optimal formulation for the cementitious material—comprising 70% （mass fraction， the same below） AH， 20% HPG， 0.3% polycarboxylic acid superplasticizer （PCE）， 7% CAS， and 3% CaO—exhibits excellent rapid-setting properties， with an initial setting time of 0.3 h and a final setting time of 0.5 h. This cementitious material achieves a compressive strength of 20.8 MPa after 1 d （29.0 MPa when completely dry）， 35.0 MPa after 3 d （38.1 MPa when completely dry）， and 39.8 MPa after 28 d （45.7 MPa when completely dry）， softening coefficient of 0.89 and a PG utilization rate as high as 90% （AH 70%， HPG 20%）. Ultimately， the hydration rate， setting time， and pore structure of this cementitious material are synergistically controlled， leading to the successful preparation of AHCSO with rapid-setting and high-strength properties.

Preparation and Mechanism of Mold-Resistant Phosphogypsum Using Composite Antifungal Agents and Alkali-Activated Materials

PENG Zhu, LI Ziling, DING You, CHENG Jinke, ZHANG Yu

2026, 45(9):  3202-3221.  doi:10.16552/j.cnki.issn1001-1625.2026.0209

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Phosphogypsum building materials are prone to mold contamination in warm and humid regions， which restricts their comprehensive utilization. To address this issue， an organic antifungal system composed of tetradecyltrimethylammonium chloride （TTAC） and polyhexamethylene biguanide hydrochloride （PHMB） was developed in this study， and coupled with a CaO-slag-aluminate cement alkali-activated system to synergistically improve the mold resistance and mechanical performance of phosphogypsum. An antifungal model was established through microstructural analysis and theoretical calculation， and the mold inhibition mechanism was discussed. The results show that the synergistic "membrane disruption-penetration" effect of TTAC and PHMB reduces the combined fungistatic index to 0.15 to 0.75， significantly lowering the minimum inhibitory concentration. The alkali-activated system refines the average pore diameter of the matrix to 0.104 μm by promoting the formation of ettringite and C-S-H gel， forming a dense physical barrier. The antifungal agents are stably immobilized in the gel network via the "electrostatic anchoring-hydrogen bond crosslinking" mechanism， which， together with the pore barrier and alkaline environment， constitutes a triple synergistic antifungal mechanism involving physical barrier， chemical sustained release and metabolic inhibition. After optimization， the specimens maintain Grade 0 mold resistance in a high-humidity environment for 28 d， with a compressive strength of 11.7 MPa and a softening coefficient of 0.72， which improves the quality of phosphogypsum wall materials and promotes the large-scale consumption of phosphogypsum.

Effect and Mechanism of Carbonation Curing on Mechanical Properties and Water Resistance of Phosphogypsum-Based Composite Cementitious Materials

CHEN Mingsheng, YANG Ning, LIU Tianle, ZHENG Shaojun, LIU Peng

2026, 45(9):  3222-3232.  doi:10.16552/j.cnki.issn1001-1625.2026.0384

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Phosphogypsum-based materials have poor water resistance and insufficient strength， which limits their large-scale resource utilization. In this paper， phosphogypsum-based composite cementitious material （PGC） was constructed by using hemihydrate phosphogypsum as the main raw material， mixed with cement， fly ash and quicklime. The effects of standard， water bath and carbonation curing on the mechanical properties， water resistance and microstructure of PGC were studied. The results show that the 28 d compressive strength of PGC under three curing conditions is significantly higher than that of single phosphogypsum system， and the compressive strength under standard curing is the highest， reaching 33.78 MPa. Under carbonation curing， PGC has both high strength and excellent water resistance. The 28 d compressive strength is 27.68 MPa， the compressive softening coefficient is 1.0. The results of TGA， XRD， FTIR and SEM show that calcium silicate hydrate （C-S-H）， AFt and CaCO₃ are synergistically formed by cement hydration， fly ash-lime pozzolanic reaction and carbonation deposition. CaCO₃ is mainly deposited in crystal gaps， gel pores and local microcracks， and improves the continuity of microstructure together with hydration products. Carbonation curing can effectively improve the strength-water resistance synergy of PGC， which can provide reference for high-value utilization of phosphogypsum， CO₂ sequestration and development of low-carbon cementitious materials.

Mechanical and Deformation Properties of Calcium Carbonate Whisker Biphasic Reinforced Recycled Concrete

KANG Tianbei, GAO Mingrui, DING Xiangqun, LI Yanfeng, WANG Fengchi

2026, 45(9):  3233-3244.  doi:10.16552/j.cnki.issn1001-1625.2026.0345

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In order to improve the mechanical and deformation properties of recycled concrete， two methods of using calcium carbonate whisker （CCW） to enhance recycled aggregate （RCA） and cement matrix were proposed in this paper. The effects of two strengthening methods on the compressive strength， stress-strain relationship， shrinkage resistance and creep properties of recycled concrete were systematically studied. The results show that the better treatment schemes of the two reinforcement methods are as follows： RCA enhancement method is soaked in CCW suspension with a concentration of 3% for 2 d， and the better volume content of CCW in cement matrix reinforcement method is 2%. Under the optimal treatment scheme， compared with the unreinforced specimens， the RCA reinforcement method and the cement matrix reinforcement method increase the peak stress of the specimens by 8.6% and 6.3%， respectively. The RCA reinforcement method can significantly improve the stiffness and strength of the recycled concrete， while the cement matrix reinforcement method is more conducive to improving the post-peak ductility. The 7 d shrinkage strain decreases by 35.7% and 13.5%， respectively， and the 90 d shrinkage strain decreases by 13.2 % and 8.1 %， respectively. At 90% and 95% stress levels， the creep failure time is extended by 22.5%， 9.9% and 78.6%， 35.7%， respectively. The creep deformation is reduced by 23.5 % and 19.8 % respectively at 85 % stress level for 80 d. Microscopic analysis shows that CCW can not only fill pores and bridge cracks， but also induce the nucleation of free Ca²⁺ and accelerate the formation of hydration products through surface adsorption， thereby strengthening the old mortar and interfacial transition zone attached to the RCA surface.

Adsorption Performance and Mechanism of Norfloxacin by Fe-Mn Modified Rice Straw Biochar

CUI Yaning, QU Shu, WANG Weiqi, LIANG Chunyang, OU Xiaoxia

2026, 45(9):  3245-3256.  doi:10.16552/j.cnki.issn1001-1625.2026.0372

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With the increasingly prominent problem of antibiotic residues in water， it is of great significance to develop low-cost， efficient and environmentally friendly adsorption materials for the pollution control of antibiotics such as norfloxacin （NOR）. Biochar was prepared from rice straw， and modified by iron and manganese to adsorb and remove NOR in water. The structure and surface properties of biochar before and after modification were analyzed by FT-IR， XRD， SEM and BET. The adsorption kinetics， thermodynamic properties and adsorption mechanism of NOR on different materials were systematically investigated. The kinetic adsorption test was carried out at 298 K and pH=5.2±0.1， and the isothermal adsorption test was carried out at 298， 308， 318 K and pH=5.2±0.1. The results show that iron-manganese modified biochar （FMBC） introduces more metal active sites， exhibits a high specific surface area （222.23 m²/g） and develops mesoporous structure dominated by 2 nm to 10 nm， which is conducive to the chemisorption of NOR. The NOR equilibrium adsorption capacity of FMBC is the largest at 318 K condition， which is 69.44 mg/g. The adsorption mechanism of NOR on FMBC mainly involves many physical and chemical mechanisms such as pore filling， hydrogen bonding， π-π electron donor-acceptor interaction and so on.

Ceramics and Glass

Influence of Carbon Powder on Crystallization Behavior of Fused Silica

DENG Weijie, BAO Qifu, DONG Weixia, LIU Mingyuan, ZENG Shuai, LI Zhe, LI Yamin

2026, 45(9):  3257-3266.  doi:10.16552/j.cnki.issn1001-1625.2026.0222

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In this work， the effects of carbon powder， both individually and in combination with hexagonal boron nitride （h-BN）， on the crystallization behavior of fused silica were systematically investigated. Based on compositional variations， four experimental groups were designed： pure fused silica， fused silica with h-BN addition， fused silica with carbon powder addition， and fused silica with a co-addition of carbon powder and h-BN. Following heat treatment at 1 250 ℃ for 0.5 h， various characterization techniques were comprehensively employed to evaluate the effects of carbon powder on the degree of crystallization， microstructure， and thermal behavior of the fused silica. Experimental results demonstrate that the addition of carbon powder significantly accelerates the formation of the cristobalite phase. Notably， in the carbon/h-BN co-addition system， the carbon powder effectively overcomes and even completely negates the crystallization-inhibiting effect of h-BN. Consequently， the degree of crystallization approaches or even exceeds that of the pure fused silica samples without any added inhibitors. Furthermore， excessive carbon powder severely impedes the densification process of the samples， leading to the deterioration of mechanical properties and an increase in the coefficient of thermal expansion. This study highlights that the interaction mechanisms between carbon impurities and h-BN must be considered when evaluating the high-temperature service reliability of fused silica and controlling raw material purity in practical production. These findings provide a crucial theoretical basis for raw material management， process optimization， and lifespan prediction of high-purity silica-based materials under complex operating conditions.

Effect of Carbon Black on Microstructure and Mechanical Properties of Fused Deposition Modeling 3D-Printed Silicon Carbide Ceramics

QIN Shuni, DONG Haolin, ZHANG Shuai, LIANG Haozhang, LIU Ziyu, LIU Peng, YANG Xianfeng, LUO Deping

2026, 45(9):  3267-3279.  doi:10.16552/j.cnki.issn1001-1625.2026.0223

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Pressureless sintered silicon carbide （SSiC） ceramics have broad application prospects in aerospace and other fields due to their excellent mechanical properties and thermal stability. In this study， SiC ceramics were prepared by fused deposition modeling （FDM） combined with pressureless solid-state sintering. The effects of carbon black specific surface area （10， 80， 150， and 230 m²/g） and content （2.0%， 2.5%， 3.0%， 3.5%， and 4.0%， mass fraction） on the printing performance as well as the microstructure and mechanical properties of the sintered bodies were systematically investigated. The results show that when the specific surface area of carbon black is 150 m²/g and the content is 3.5%， feedstock ensures extrusion stability while achieving good shape retention. Under these conditions， the green body density reaches 2.18 g/cm³， and the flexural strength is （16.2±2.0） MPa. Too low specific surface area or insufficient content of carbon black leads to an incomplete carbothermal reduction reaction； whereas too high specific surface area or excessive content induces carbon black agglomeration， thereby inhibiting the densification process. After pressureless sintering at 2 150 ℃， when the specific surface area of carbon black is 150 m²/g and the content is 3.5%， the silicon carbide ceramic achieves a density of 3.02 g/cm³， a flexural strength of （344.0±52.0） MPa， and a hardness of （24.2±1.2） GPa. Using this process， various complex components were successfully fabricated using this process. This study provides a new approach for the fabrication of complex silicon carbide components by fused deposition modeling.

Structure and Mechanical Properties of Magnesium Aluminum Spinel Ceramics Strengthened by Manganese Ion Diffusion

XUAN Songtong, KONG Xiangchen, WANG Kaiyue, TIAN Yuming

2026, 45(9):  3280-3288.  doi:10.16552/j.cnki.issn1001-1625.2026.0124

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To prepare high-performance magnesium aluminum spinel structural ceramics， this study used bauxite and magnesite as raw materials and pyrolusite as an additive to prepare MgAl₂O₄ ceramics via a solid-state sintering method. The effect of the additive on the spinel structure was analyzed， the role of manganese ions in modifying impurity phases was elucidated， and the mechanism by which manganese ion diffusion enhanced the densification and mechanical properties of MgAl₂O₄ was revealed. The results show that adding pyrolusite to the natural raw materials allow Mn²⁺ to dissolve into the MgAl₂O₄ lattice， forming a （Mn _x Mg_1-x ）Al₂O₄ solid solution. This process weakens the Kirkendall effect， reduces porosity on the MgO side during spinel formation， enhances the diffusion and mass transfer rate of Mg²⁺， and improves the densification and flexural strength of the samples. Meanwhile， the reaction between Mn²⁺ and anorthite generates johannsenite and Al₂O₃， which induces lattice distortion in the pyroxene， increases the concentration of lattice defects， and further promotes the ions diffusion rate. When the pyrolusite addition reaches 3% （mass fraction）， the bulk density of the material reaches 3.29 g/cm³， the apparent porosity decreases to 0.24%， and the flexural strength increases to 140.2 MPa.

Microstructure and Mechanical Properties of Transparent Li₂O-SiO₂ Microspheres Prepared by Plasma Melting

WEN Bin, ZHANG Hanxiao, WU Yuesheng, XIE Jun, ZHANG Jihong

2026, 45(9):  3289-3298.  doi:10.16552/j.cnki.issn1001-1625.2026.0198

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In this study， Li₂O-SiO₂ transparent microspheres with different compositions were fabricated via a combined spray granulation and plasma melting spheroidization process. Their microstructure， structural characteristics， and mechanical properties were systematically investigated. The results indicate that， after spheroidization in the Li₂O-SiO₂ system， increasing the mole fraction of Li₂O induces a structural transformation from an amorphous to a crystalline state. Meanwhile， the silicate network gradually depolymerizes， the proportion of non-bridging oxygens increases， and the structural units evolve from highly polymerized to less polymerized configurations. Mechanical testing demonstrates that the Vickers hardness and elastic modulus of the microspheres are strongly dependent on composition and structure. Samples with lower Li₂O content （33.3%， mole fraction） exhibit higher hardness and modulus values， with a maximum Vickers hardness of 5.83 GPa and an elastic modulus of 83.39 GPa. This research provide a valuable reference for the composition design and mechanical performance control of silicate microspheres. The fabricated microspheres have potential applications in functional structural materials.

Road Materials

Preparation and Properties of Cement-Based Repair Materials for Road

ZHANG Yibin, LUO Jianlin, SHANG Huaishuai, JING Yuan, LIU Chao

2026, 45(9):  3299-3316.  doi:10.16552/j.cnki.issn1001-1625.2026.0163

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To ensure the service life of modern roads and driving safety， fast repairing damaged roads with high-performance repair materials is an efficient and environmentally friendly approach. In this paper， Portland cement and sulfur-aluminate cement were combined to form a compound cementitious system. Recycled tire rubber powder （RP） and dispersible latex powder were added simultaneously， and graphene oxide was further introduced to prepare a nanomaterials/polymer/rubber ternary modified cement-based composites （NPRM）. The orthogonal optimization method was used to comprehensively and quantitatively analyze the various repair properties of NPRM. After conducting the analysis of variance， the optimal ratio of NPRM is determined. The flowability， final setting time， 28 d flexible/compressive strength ratio， 28 d flexural tensile bond strength， and 90 d drying shrinkage of NPRM with the optimal ratio are 194 mm， 115 min， 0.319， 5.35 MPa， and 93.57×10^-6， whose comprehensive repair performances are superior to those of traditional repair mortar. Moreover， the incorporation of RP can significantly reduce the impact and noise generated by vehicle loads， hereafter achieves energy absorption and sound absorption effect when use NPRM to repair deteriorated urban roads.

Design and Application of Composite Solidified Agent for Stabilizing Iron Tailings Sand

DONG Yonggang, JIA Hongjun, PAN Yating, MA Xikai, JIANG Hui, ZHOU Qiang, CHEN Xiao

2026, 45(9):  3317-3329.  doi:10.16552/j.cnki.issn1001-1625.2026.0186

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To address the problems of low strength， insufficient strength growth rate， and large shrinkage of iron tailings sand stabilized materials， a composite solidified agent was prepared from ordinary Portland cement clinker， ground granulated blast-furnace slag powder， and gypsum， and the effects of its composition and dosage of the solidified agent on the mechanical properties， volumetric stability， and durability of iron tailings sand base mixtures were investigated. The results show that the mechanical properties of iron tailings sand stabilized with the solidified agent improve significantly with increasing clinker content. Gypsum exhibits an optimum content， and when the gypsum content is 15% （mass fraction）， the 7 d unconfined compressive strength of iron tailings sand stabilized with the solidified agent reaches 3.43 MPa. Moreover， the drying shrinkage of iron tailings sand stabilized with the solidified agent is markedly reduced with increasing gypsum content. The optimum proportion of the solidified agent is identified as m（clinker）∶m（slag）∶m（gypsum）=15∶70∶15. Compared with cement-stabilized iron tailings sand base mixtures at the same binder dosage， iron tailings sand stabilized with the solidified agent exhibits up to a 46.26% increase in the 180 d strength growth rate and up to a 41.47% reduction in drying shrinkage strain， while water stability and freeze-thaw resistance are also improved. Microstructural analysis shows that a large amount of C-S-H gel forms at later ages in iron tailings sand stabilized with the solidified agent， which significantly enhances later-age strength development rate. Meanwhile， gypsum promotes the early formation of abundant needle- and rod-like ettringite crystals and induces slight expansion， which effectively compensates for the drying shrinkage of iron tailings sand base mixtures and significantly reduces the risk of cracking.

Effects of Quarry By-Products on Performance of Cement-Stabilized Iron Tailings Pavement Base Materials

CHEN Xiao, MA Xikai, JIANG Rui, SHU Yang, HUANG Min, HUANG Shijie

2026, 45(9):  3330-3340.  doi:10.16552/j.cnki.issn1001-1625.2026.0254

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Applying quarry by-product （QBP） to cement-stabilized iron tailings pavement base material for roads can improve the problems such as insufficient strength and shrinkage cracking of the base material caused by the fine particles of iron tailings sand， thereby achieving large-scale resource utilization of iron tailings. This paper systematically studied the effects of QBP content and the fine particle plasticity index （particle size d<0.075 mm） on the mechanical properties， volume stability， and durability of cement-stabilized iron tailings. The shrinkage strain was regulated by an expansion agent， and the mechanism of QBP was revealed through microscopic analysis. The results show that when the QBP content is 40%（mass fraction）， compared with the unmodified group， the 7 d unconfined compressive strength increases by 48.37%， the shrinkage strain decreases by 42.50%， and the frost resistance coefficient and water stability coefficient increase by 15.22% and 13.83%， respectively. Increasing the fine particle plasticity index improves the mechanical and durability properties of cement-stabilized iron tailings， but it also increases the risk of shrinkage cracking. After adding expansion agent， the shrinkage strain decreases by 48.69% compared with the unadulterated group， and is almost equivalent to the shrinkage strain of cement-stabilized crushed stone of the same strength grade. Microscopic analysis shows that QBP can optimize the packing structure of the cement-stabilized iron tailings mixture， improve the density and reduce the porosity， thereby improving the road performance.