In order to ensure the working time, the magnesium phosphate cement coating needs to be mixed with a large amount of retarder under the conventional spraying process, which not only weakens the early hour strength of the coating, but also increases the cost of raw materials. Based on this, this paper adopted the integrated spray printing equipment with mixing and spraying function, and realized the preparation and spraying construction of the ultra-rapid setting magnesium phosphate cement coating without retarder by the spray mode of dry powder inlet and wet material outlet. The development law of bonding strength of the coating under different curing environments and the improvement effect of frost resistance under freeze-thaw cycle were further studied. The results show that when the magnesium-phosphorus molar ratio (M/P) is 6 and the water-binder ratio (W/B) is 0.18, the bonding strength of the ultra-rapid setting magnesium phosphate cement coating is the best, and the bonding strength can reach 2.46 MPa after 60 d. Compared with the air curing at the same age, the bonding strength of the ultra-rapid setting magnesium phosphate cement coating in the early stage of seawater and salt lake brine curing is significantly increased by 43.2% and 22.5%, respectively. In the early stage of curing, seawater and salt lake brine can promote the hydration reaction of unreacted magnesium oxide and potassium dihydrogen phosphate in the coating to generate more struvite, thereby enhancing the bonding strength of the coating. The bonding strength of the coating decreases slightly at the later stage of curing, but it can still be maintained 0.84 MPa. Compared with uncoated concrete, the compressive strength retention rate and relative dynamic elastic modulus of ultra-rapid setting magnesium phosphate cement coated concrete increase by 111.5% and 33.1%, respectively, and the mass loss rate decreases by 76.3% after 150 times freeze-thaw cycles. The research results provide a theoretical basis for the application of spray printing ultra-rapid setting magnesium phosphate cement coating in concrete structure protection engineering under harsh environment.

This study used cement as the primary material to investigate the effects of mixing water temperature and proportion of hydrogen peroxide on the mechanical properties, thermal insulation, and pore structure of foamed cement. By adjusting the water temperature (40, 50, 60 ℃) and proportion of hydrogen peroxide (6%, 7%, 8%, mass fraction), cement with varying densities were prepared via the chemical foaming method. The compressive strength, thermal conductivity, and pore structure of the foamed cement were thoroughly analyzed. The results show that when the water temperature is controlled at 50 ℃ and the proportion of hydrogen peroxide is 7%, the compressive strength of the foamed cement reaches 1.93 MPa, the thermal conductivity is 0.054 1 W/(m·K), the pore distribution is uniform with a dense structure. By appropriately regulating the proportion of hydrogen peroxide and water temperature, the compressive strength and thermal insulation performance of foamed cement can be significantly enchanced. At the same time, the pore structure distribution can be optimized, and the overall performance of foamed cement can be improved.

Aiming at the problem of fast setting time and poor workability of fast-setting and fast-hardening high belite calcium sulfoaluminate (HB-CSA) cement, the effect of ethylenediamine tetramethylene phosphonic acid (EDTMP) on the setting time, fluidity and mechanical properties of HB-CSA cement was investigated by hydration heat, X-ray diffraction, thermogravimetric and mercuric pressed tests. The mechanism of action of EDTMP in HB-CSA cement was analyzed. The results show that EDTMP can effectively retard the setting time of calcium sulfoaluminate cement and improve the fluidity. When the EDTMP contnet is 1.00% (mass fraction), it can prolong the initial setting time of HB-CSA cement to 62 min and prolong the final setting time of HB-CSA cement to 76 min. EDTMP can inhibit the reaction between anhydrous calcium sulfoaluminate (C4A3Sˉ) mineral and gypsum phase of HB-CSA cement in order to inhibit the rapid generation of ettringite (AFt), which is an early hydration product of cement, so that HB-CSA cement retarding can be achieved.

The purpose of this paper was to explore the effect of nano calcium aluminosilicate hydrate (C-A-S-H) and diethanol monoisopropanolamine (DEIPA) composite on the early hydration, setting time, chemical shrinkage and compressive strength of cement at different curing temperatures. The mechanism was analyzed by hydration heat, XRD, TG and SEM. The results show that after adding nano C-A-S-H and DEIPA at different curing temperatures, the hydration rate of silicate and aluminate is accelerated, more hydration products are formed in the system, and the setting time of cement is shortened. When the curing temperature is 10 ℃, the initial setting time and final setting time are shortened by 13.06% and 11.75% respectively compared with the blank group. At the curing temperature of 0, 10 and 20 ℃, the chemical shrinkage increases by 20.00%, 13.79% and 9.30% respectively compared with the blank group at age of 24 h. The compressive strength of cement mortar increases compared with the blank group. When the age is 24 h, and the curing temperature is -15, 0, 10 and 20 ℃, the compressive strength increases by 94.48%, 85.91%, 55.93% and 23.17%, respectively.

In view of the engineering requirements for the co-processing of nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the flue gas of waste in cement kiln, a series of CuCe-MCM-41 loading catalysts with different Cu/Ce doping ratios were prepared by impregnation method. The performance of catalytic removal of toluene and NOx in the pre-calcining system of cement kiln and the reasons for its excellent performance were discussed. The results show that the prepared Cu2Ce1-MCM-41 catalyst has a toluene conversion rate of more than 90% at 450~600 ℃, and the NOx conversion rate is close to 60% at 800~1 000 ℃. It shows that the Cu2Ce1-MCM-41 catalyst still has a certain denitration activity after catalytic oxidation of toluene. The introduction of Cu2+ and Ce3+ significantly increases the acidity and the number of active sites on the surface of MCM-41 molecular sieve, and the oxidation reduction cycle promotes the formation of oxygen vacancies. Therefore, the Cu/Ce coading MCM-41 catalyst shows excellent catalytic oxidation of toluene and denitration activity. It is expected to combine the cement process to remove VOCs from flue gas, greatly reduce the NOx concentration entering the NH3-SCR flue gas, prolong the service life of catalyst, and reduce NOx abatement costs.

Basalt fiber reinforced high-strength mortar (BFHSM) has a bright prospect of applications in engineering due to its lightweight, high strength, and great durability. The mechanical properties and durability after high temperature are important indicators for evaluating structural safety performance. In this paper, the effect of temperature (20, 100, 150, 200, 250, 300, 350, 400 ℃) on the mechanical properties and the chloride ion penetration resistance of BFHSM with basalt fiber (BF) content of 0% (volume fraction, the same below) and 1.0% were investigated by high temperature test, compressive strength test, splitting tensile strength test, XRD analysis, and chloride ion penetration resistance test. The results show that the compressive strength and splitting tensile strength of BFHSM increase first and then decrease, and the compressive strength and splitting tensile strength can be improved with BF. XRD results indicate that the hydrated calcium silicate (C-S-H) gel, dicalcium silicate (C2S) and tricalcium silicate (C3S) in BFHSM matrix gradually decrease after the temperature exceeds the critical temperature, which is the main reason for the decrease in compressive strength of BFHSM. Also, the incorporation of BF can improve the chloride ion penetration resistance of BFHSM. Compared with the control group, the electric flux of BFHSM decreases by 19.82%, 5.33%, 7.61%, and 2.21% after 20, 100, 200 and 300 ℃, respectively. Moreover, the chloride ion penetration resistance of BFHSM decreases with the increase of temperature.

Polyacrylamide (PAM) generated during the sand washing process exerts an impact on the workability and mechanical properties of cement mortar. This research investigated the effect of PAM content on the setting time, initial fluidity and time-dependent fluidity loss rate and strength of cement paste and cement mortar. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the effect of PAM on the hydration process of ordinary Portland cement. Additionally, the effects of different types and content of water reducers and low-temperature heat treatment PAM sand on the fluidity and mechanical properties of cement mortar were examined. The results indicate that with the increase of PAM content, the final setting time of cement paste increases, the initial fluidity of cement mortar decreases, the time-dependent fluidity loss rate increases, and the 7 and 28 d strengths of cement mortar increases and then decline. The incorporation of PAM scarcely alters the cement hydration products, but suppresses the cement hydration process. The addition of water reducer can enhance the fluidity of cement mortar. Low-temperature heat treatment of PAM-containing sand at 240 ℃ can improve the fluidity and strength of cement mortar.

Calcium silicate hydrate (C-S-H) is the main hydration product of cement-based materials and contains internal gel pores, which significantly influence the durability of concrete. To investigate the creep deformation mechanism of C-S-H at the microstructure level, based on a molecular model of C-S-H gel, the creep performance of C-S-H under different various uniaxial loading directions and with gel pore defects of different sizes were studied by molecular dynamics simulation. The results indicate that C-S-H has better creep resistance along the calcium silicon layer, but poorer creep resistance in the direction perpendicular to layer. During the creep process, the creep resistance of Ca—O ionic bonds and Si—O covalent bonds are stronger than that of hydrogen bonding network structures, and the compressive creep resistance of C-S-H is superior to the tensile creep resistance. Microstructure analysis indicates that the creep primarily originates from the interlayer region, and deformation mainly caused by the displacement of interlayer atoms, among which water molecules make the most significant contribution to creep deformation. Furthermore, the gel pore defects will reduce the creep resistance of C-S-H, and significantly affect the creep rate in the initial creep stage.

Under high temperature conditions, the presence of defects and confined water in C-S-H gel significantly affects its strength and durability. This study employed reactive molecular dynamics to investigate the molecular structural characteristics and reactivity of type I defect C-S-H gel under high temperature environments. The findings reveal that the increase in temperature and Ca/Si ratio enhances the mobility of water molecules, accelerating their penetration into the layered structure, reducing structural order and connectivity, leading to an increase in Q1 and Q0, and weakening the thermal stability of C-S-H gel. Type I defect causes the C-S-H gel to expand along the interlayer direction, and the expansion rate increases with rising temperature and Ca/Si ratio. Under high temperature and high Ca/Si ratio conditions, the reactivity of water molecules is enhanced, promoting hydrolysis reactions and the formation of hydroxyl groups, and type I defect rapidly expands, significantly affecting the structural stability of gel. The results of this study provide theoretical support for improving the performance of concrete in extreme environments such as fires.

To investigate the frost resistance and durability performance of high-ductility engineered cementitious composites (ECC) made with Yellow River sand, the rapid freeze-thaw cycle test was carried out to study the mass loss rate, relative dynamic elastic modulus, cube compressive strength and splitting tensile strength of ECC materials under different Yellow River sand replacement rate. Based on the multidimensional evaluation of the replacement rate of the Yellow River sand, the optimal replacement rate was obtained. The microscopic characteristics and frost resistance mechanism under the optimal replacement rate were further analyzed by means of scanning electron microscope and X-ray computed tomography tests. The results show that the relative dynamic elastic modulus of the five groups of ECC specimens is not less than 97% after 150 freeze-thaw cycles, and the compressive strength and splitting tensile strength increase with the increase of the replacement rate of Yellow River sand. The results of multidimensional evaluation analysis show that the frost resistance of Yellow River sand ECC is the best at 100% frost rate. Microscopic analysis shows that the pore distribution is uniform, the proportion of small pores is high, the degree of internal hydration is high, and the fiber adhesion is good. The freeze-thaw damage model based on Weibull probability distribution can better predict the freeze-thaw damage state of Yellow River sand ECC.

In this study, fiber pullout tests were conducted under varying fiber embedment depths and loading rates to investigate the interfacial bonding properties of glass-sand ultra-high performance cementitious composite (GS-UHPCC). Quantitative analysis was performed on the interfacial bonding properties and mechanical properties of steel fibers and the matrix. Furthermore, the load-slip model of steel fiber was established. The results show that the interfacial bonding properties between steel fiber and GS-UHPCC are significantly improved with the increase of fiber embedment depth. When the fiber embedment depth increases to 12 mm and 18 mm, the pullout peak load of steel fiber increases by 43.81% and 87.56%, respectively, compared with specimen with fiber embedment depth of 6 mm. Similarly, the pullout energy increases by 63.27% and 176.36%, respectively. In addition, the interfacial bonding properties between steel fiber and GS-UHPCC exhibit obvious rate sensitivity. When the loading rate increases from 0.5 mm/min to 5.0 mm/min, the average increases of the pullout peak load and pullout energy of steel fiber are 27.16% and 127.98%, respectively. The load-slip model considering the steel average bonding strength and decayed bonding strength can effectively characterize the interfacial behavior between the steel fibers and the matrix.

In order to reduce the risk of cracking of high strength mass concrete due to significant early self-shrinkage and temperature drop shrinkage, the effect of temperature rise inhibitor (TRI) dosage on the hydration heat release process, setting time and mortar strength of pure cement and cement-7% (mass fraction) calcium and magnesium oxides based expansive agent (CMEA) composite cementitious materials were studied, and the effect on the adiabatic temperature rise and deformation properties of concrete with 7%CMEA was also investigated. The results show that the increase of TRI dosage can reduce the early hydration heat release rate, heat release and early strength of pure cement and cement-7%CMEA composite cementitious materials, and prolong the setting time, but it has little effect on the late strength. After adding 0.20% (mass fraction) TRI, the 1 d cumulative heat release of CMEA cement decreases by 26.7%, and the 1 d adiabatic temperature rise of CMEA concrete decreases by 31.1%. In addition, the expansion deformation peak value of CMEA concrete increases by 288 in the temperature rise stage compared with 0.15%TRI, and the shrinkage deformation decreases by 7.2% in the temperature drop stage, which is more conducive to reducing the early concentrated heat release of high strength mass concrete and improving its crack resistance.

In order to investigate the effect of nano-SiO2 on resistance of concrete to sulfate attack, concrete specimens mixed with 0%, 0.5%, 1.0%, 2.0%, and 3.0% (mass fraction, same as below) nano-SiO2 were immersed in 5% (mass fraction) sodium sulfate solution for sulfate attack experiment in this paper. The effects of concrete specimens mixed with nano-SiO2 on mass change, relative dynamic elastic modulus, loss coefficient of compressive strength, and resistance to sulfate attack in the accelerated sulfate attack experiment by wet-dry cycling were investigated. The results show that as the content of nano-SiO2 increases, mass loss rate, relative dynamic elastic modulus and loss coefficient compressive strength of the concrete show an increasing and then decreasing trend. Compared with the NS0 group specimens, when the nano-SiO2 content is 2% the performance of concrete is the best. Through X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis mechanism, it is found that the addition of nano-SiO2 has a good improvement effect on improving the internal microstructure of concrete. Nano-SiO2 can accelerate the hydration reaction inside the cement, promote the formation of hydrated calcium silicate gel, and form an interlaced dense network structure inside, further improving the compactness and resistance of concrete to sulfate attack.

To address the rapid deterioration of concrete durability under combined salt freezing erosion in cold-arid regions, this study designed experimental schemes with varying basalt fiber volume fraction and length through laboratory freeze-thaw tests. Using deionized water and a composite salt solution (3% (mass fraction) NaCl+5% (mass fraction) Na2SO4) as erosion media, this paper investigated the evolution of concrete’s durability properties during freeze-thaw cycles. Nuclear magnetic resonance (NMR) technology was employed to measure porosity variations in concrete specimens under different conditions, and a fractal dimension model was developed to analyze pore size distribution characteristics. Results show that basalt fiber incorporation effectively improves concrete’s mechanical properties and reduces salt-freeze erosion damage. Both relative dynamic elastic modulus and compressive strength initially increase then decrease with increasing basalt fiber content. Fiber incorporation reduces concrete’s internal porosity. The fractal dimension model indicates optimal pore structure densification occurs at 0.15% (volume fraction) fiber content and 25 mm length. Results from NMR tests and fractal modeling show good agreement with experimental data. The findings provide both theoretical basis and technical references for optimizing and maintaining hydraulic concrete in cold-arid regions.

As a new type of shear connector in composite beams, bolts can improve the degree of structural assembly and avoid welding defects. In this paper, static and fatigue tests were carried out on 13 groups specimens. The evolution of friction performance of steel-concrete composite interface through bolted joints under fatigue loading was explored. The static friction bearing capacity of steel-concrete composite interface and the relative slip, shear stiffness, bolt preload and friction coefficient after wear under cyclic load were obtained. The results show that there is no fatigue failure of the friction shear connection after 2 million cycles. The pre-tightening force of the bolt continues to decay during the cycle and is positively correlated with the peak load, with a loss of about 8.38%. The friction coefficient of interface after wear decreases to the lowest value of 0.486 after 100 000 cycles, but it continues to increase and even exceeds the initial static friction coefficient. Due to the change of occlusion shear and the migration of abrasive particles, the depth of wear marks increases first and then decreases, which explains the evolution mechanism of fatigue of friction performance of concrete interface at the micro scale. The research results provide some reference for the design of friction bolt shear connectors.

In order to enhance the mechanical properties and durability of tunnel shotcrete, a high-performance shotcrete admixture (referred to as high-performance admixture) for tunnel shotcrete was developed in this paper. By means of hydration heat, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), the mechanism of high-performance admixtures to improve the mechanical properties, rebound rate and durability of shotcrete was studied. A predictive model for relative dynamic elastic modulus was established based on the number of freeze-thaw cycle and high-performance admixture content in shotcrete. The results show that the high-performance admixture promotes cement hydration process, increases hydration product formation, and refines pore structure in hardened cement, resulting in denser microstructure that enhances both strength and durability. When the content of high-performance admixture is 10% of the mass of cementitious material, the compressive strength of shotcrete increases by 51.7% and the rebound rate decreases by 54.5% compared with the reference group.

Concrete engineering in cold regions is often damaged by freeze-thaw in varying degrees, but currently, there is limited research on the re-service of concrete after damage repair in freeze-thaw environments. To study the effect of freeze-thaw cycles on the mechanical properties of cracked concrete specimens with grouting repair by different materials, cracked concrete specimens were prepared and repaired by grouting with ordinary Portland cement (OPC) and epoxy resin polymer (ERP), and freeze-thaw cycle tests and uniaxial compression tests were conducted on the grouting repair specimens. By using particle flow code (PFC) to establish models of different bonding modes, the freeze-thaw cycle simulation of concrete was realized based on the water ice particle phase transition coupled expansion method. By combining with indoor tests, the study explored the variations in mechanical properties, crack propagation, and failure modes of specimens across different freeze-thaw cycles. The test results show that with the increase in the freeze-thaw cycles, the apparent freeze-thaw deterioration state of the grouting repair specimens gradually increase, and the quality increases first and then decreases. The development of freeze-thaw damage accelerates in the later stages of freeze-thaw cycles, and the frost resistance of ERP repaired specimens is better than that of OPC repaired specimens. The simulation results show that the bonding performance between grouting materials and concrete has a significant impact on the degree of freeze-thaw deterioration of the slurry-concrete bonding interface layer, leading to differences in the frost resistance of the specimens. As the number of freeze-thaw cycles increases, the accumulation of freeze-thaw damage will change the main crack propagation path of the specimen, resulting in a change in the failure mode of the specimen. The strength and bonding performance of grouting materials can change the stress state of the specimen and affect its crack propagation law.

Under the effect of “three highs and one disturbance”, the surrounding rock of deep coal mine roadways is prone to continuous large deformation, coal and rock softening and poor permeability. In this study, acrylamide (AM) monomer was used to in-situ polymerize and modify sulfoaluminate cement grouting material (SCGM), and the effect of AM dosage on the slurry property, mechanical properties and microstructure of SCGM was systematically studied, and its toughening mechanism was discussed. The results show that AM can improve the fluidity of slurry, but when the AM dosage reaches 30% (mass fraction), the initial setting time of slurry is greater than 50 min, and the maximum reaction temperature is greater than 80.0 ℃, which affects the self-sealing effect and safety of slurry. In-situ polymerization modification of AM can enhance the bonding strength between stone body and coal body, and significantly improve SCGM toughness. When the AM dosage is 20%, compared with control group, the coal bonding strength at 28 d increases by 20.6%, the relative compressive relative toughness at 28 d increases by 35.4 times, and the tensile relative toughness at 28 d increases by 15.2 times. The field application results of the 2715 lower roadway in Cheji Coal Mine show that the SCGM modified by in-situ polymerization of AM with a dosage of 20% has a better effect on improving the integrity and stability of coal rock, and the shrinkage rate of roadway after excavation for 100 d is controlled within 2%. This study provides a high-toughness material for the field of deep coal mine roadway surrounding rock grouting reinforcement, which is of great significance for the stability and safety guarantee of deep coal mine roadway.

Rubber cement-based materials provide a new idea to the utilization waste rubber. Waste rubber tires are ground into rubber particles and incorporate into cement-based materials to produce rubber cement-based materials. Compared with ordinary cement-based materials, rubber cement-based materials exhibit varying degrees of improvement in toughness, impact resistance, and durability, and have become a hot topic in the research of road construction materials. This article summarizes and analyzes the research results on the durability of rubber cement-based materials in recent years both domestically and internationally. The results show that adding rubber to cement-based materials can improve the impermeability, frost resistance, carbonation resistance and salt corrosion resistance to varying degrees. By modifying rubber, its surface morphology can be changed, and the adhesion between the rubber and cement interface can be improved, thereby improving the durability of the rubber cement-based materials. This paper aims to provide references and inspiration for further research on rubber cement-based materials both domestically and internationally.

Copper tailings (CTs), as one of the major industrial solid wastes, have garnered significant attention due to their potential for comprehensive resource utilization. Currently, the cumulative reserves of CTs in China account for approximately one-quarter of the total tailings volume, second only to iron tailings, indicating a large reserve. However, the development of tailings recycling technologies in China is relatively slow, and the utilization efficiency of CTs remains is low. It is urgent to explore a reasonable and efficient methods for CTs. While research on the application of CTs in cement and concrete has been extensive, these studies typically focus on specific aspects of performance or application research, with relatively few comprehensive reviews available. This paper categorizes the use of CTs in cement production and concrete application, reviews the fundamental properties of CTs, as well as their application characteristics and advantages in cement and concrete, and provides a summary and outlook on the control of heavy metal ion leaching and activation techniques for CTs. The goal is to offer technical and theoretical support for the comprehensive and efficient utilization of CTs.

The active Si/Al ratios of metakaolin-based geopolymer raw materials are closely related to their mechanical properties. In this study, the content of active Si and active Al in metakaolin were determined by acid leaching-alkali dissolution method and the complexometric titration method. By adding active Si and active Al and employing characterization techniques such as XRD, FTIR, DSC-TG, and SEM, the effects of different active Si/Al ratios on the geopolymerization process and mechanical properties of metakaolin-based geopolymers were investigated from the perspectives of material composition and microstructure. The results show that the acid leaching-alkali dissolution method and the complexometric titration method can effectively quantitatively analyze the contents of active Al and active Si in metakaolin. With the increase of active Si/Al ratio, the 3 d compressive strength of the metakaolin-based geopolymer initially increases and then decreases. When the active Si/Al ratio is relatively low (0.4~0.8), the “encapsulation effect” in the metakaolin-based geopolymer system leads to an increase in unreacted aluminosilicates, and the structure with numerous pores and cracks, resulting in low compressive strength. When the Si/Al ratio is relatively high (2.2~2.4), the system forms zeolite structure and becomes a multiphase system, and the compressive strength is also low. When the active Si/Al ratio is 1.0, the degree of geopolymerization reaction is maximized, yielding the highest amount of gel phase and the best compressive strength, with a compressive strength of 33.7 MPa. These findings provide a theoretical basis for the regulation of the compressive strength in metakaolin-based geopolymers.

To realize efficient resource utilization of coal gangue, the influences of modification treatments on performance of coal gangue mortar using coal gangue fine aggregate were investigated. Coal gangue fine aggregate was modified through fly ash-cement slurry encapsulation modification, CO2 mineralization combined with fly ash-cement slurry encapsulation modification, and epoxy resin encapsulation modification methods. The aim was to study the influences of these coal gangue fine aggregate modifications on the working performance, mechanical properties, and microstructure of coal gangue mortar to elucidate their mechanisms. The results demonstrate that compared to unmodified coal gangue mortar, the modified coal gangue mortar exhibits improved water absorption, mechanical properties, and microstructure. Among these modifications, epoxy resin encapsulation modification proves most effective with a 28.8% increase in compressive strength and a 32.4% increase in modulus of elasticity, while reducing water absorption by 25.3%. This can be attributed to the enhanced overall strength and reduced porosity of aggregates due to epoxy resin hardening, as well as improvements in interfacial transition zones, leading to enhanced mechanical properties.

The influence of vitreous content on the pozzolanic activity of fly ash is very important. In this study, low-calcium fly ash with vitreous content of 60%, 70%, 80%, and 90% (mass fraction) was selected using the XRD-Rietveld method. The influence of fly ash with different vitreous content on the micro and macro properties of cement-based materials with similar fineness was analyzed and compared, and the hydration activity of fly ash with varying vitreous content was evaluated. The results indicate that, under the premise of essentially consistent fineness, fly ash vitreous content has approximately posititve linear relationship with activity index. Fly ash with 90% vitreous content achieves an activity index of 85.1%, which is 14.6% higher than fly ash with 60% vitreous content. The most significant growth trend of activity index is observed in the fly ash with range of 70% to 80% vitreous content. The increase of vitreous content of fly ash accelerates the hydration process of composite cement at all ages and optimizes the microstructure of cement. In the later stages of composite cement hydration, fly ash with higher vitreous content significantly improves both the mechanical properties and pore structure. After 28 d, composite cement containing fly ash with 90% vitreous content shows a 7.7 MPa increase in compressive strength compared to cement with fly ash containing 60% vitreous content.

In order to solve the problems of high wet subsidence of loess in contact with water and high carbon emission of traditional cement curing agent, sodium silicate excitation granulated blast furnace slag powder was used to cure loess. The feasibility of geopolymer as an environmentally friendly curing agent to replace cement was evaluated by unconfined compressive test, scanning electron microscope and mercury-in-pressure test. The results show that the compressive strength of geopolymer-cured loess is significantly higher than that of cement-cured loess under the optimal conditions (alkali dosing of 1.5% (mass fraction), curing age of 28 d). The compressive strength of geopolymer-cured loess and cement-cured loess tend to increase and then decrease with the number of dry and wet cycles. The cumulative mass loss of the different cured loess samples after the dry and wet cycles is less than 20%. The surface fissure rate of the different cured loess samples increases with the increase in the number of dry and wet cycles. Under the action of dry and wet cycles, the geopolymer-cured loess generates more cementation products due to the secondary polymerization reaction, which improves the compressive strength. The results of this study can provide theoretical reference for the application of geopolymer-cured loess in practical engineering.

To enhance the engineering durability of the loess in various environments, this paper employed biopolymer combined fiber to treat the loess, conducted unconfined compressive tests, and explored the compressive strength of biopolymers combined with fiber-treated loess as well as its variation rule and action mechanism under the influence of drying-wetting cycles and freezing-thawing cycles. The results indicate that, in comparison to untreated loess, the compressive strength and ductility of loess are markedly enhanced when biopolymer and fiber are incorporated. Specifically, when the mixture contains 2.0% (mass fraction) biopolymer and 1.00% (mass fraction) fiber, the compressive strength of the treated loess attains its peak value of 6.47 MPa. Under drying-wetting cycles and freezing-thawing cycles, the compressive strength of both treated loess and untreated loess decrease with the increase in the number of cycles. Nevertheless, after 10 drying-wetting cycles, the compressive strength of the treated loess is 7.40 times that of the untreated loess, and after 10 freezing-thawing cycles, the compressive strength of the treated loess is 2.30 times that of the untreated loess. In summary, biopolymers combined with fiber-treated loess can effectively enhance the engineering durability of loess in drying-wetting and freezing-thawing environments.

The use of various solid wastes to prepare geopolymers can promote the engineering application of low-carbon cementitious material and the recycling of solid waste resources. This study used air-cooled nickel slag with low reactivity as the main precursor and incorporated ground granulated blast furnace slag to prepare geopolymers. The influence of ground granulated blast furnace slag content and alkali activator modulus on autogenous shrinkage and drying shrinkage were investigated. The pore structure of the hardened body was characterized by the nitrogen adsorption method, and the relationship between shrinkage performance and pore structure was explored. The results show that the increased ground granulated blast furnace slag content enhances the compressive strengths of geopolymers, and meanwhile reduces the autogenous shrinkage. The formation of calcium alumino silicate hydrate (C-A-S-H) gel phase fills into the pores in geopolymer to reduce the overall pore volume. This is helpful in constraining the capillary pore water loss under drying conditions, and consequently the drying shrinkage is mitigated. The increased alkali activator modulus enhances the capillary pore volume. The development of higher capillary pressure due to self-desiccation and water evaporation on drying results in both higher autogenous shrinkage and drying shrinkage.

The construction of filling retaining walls is one of the necessary process links in phosphate mining using the filling method. Using phosphogypsum-based blocks to build filling retaining walls is an important way to support green mining technology and the utilization of phosphogypsum resources. However, the compressive strength, permeability, and water resistance of phosphogypsum-based blocks prepared on-site near common mining sites are difficult to ensure. This paper proposed a type of special-shaped brick structure formed by extrusion process using high-temperature calcined phosphogypsum, calcium powder, cement, etc. as basic raw materials. Through indoor test block production and testing, the compressive strength of phosphogypsum-based extruded special-shaped brick (PG-ESB) meets the brick strength requirements. To clarify the internal structural characteristics of PG-ESB, the internal pore distribution characteristics of PG-ESB were studied by low-temperature liquid nitrogen adsorption test, high-pressure mercury intrusion test, scanning electron microscope (SEM), X-ray computed tomography and other methods. PG-ESB has a lower cost and its strength meets the standard for building retaining walls. The results of low-temperature liquid nitrogen adsorption test, high-pressure mercury intrusion test, and SEM show that PG-ESB has a large number of pores with a size of 0.5~2.0 m. X-ray computed tomography results further confirm that there are a large number of irregular micropores inside PG-ESB, 11.02% of the micropores are distributed in a circular shape, 85.23% of the micropores are distributed in a nearly circular or elliptical shape, and 3.75% of the micropores are in an irregular shape. To correct the shortcomings of test results, this paper proposes to use a three-parameter distribution method to completely describe the internal structural micropore distribution characteristics of PG-ESB. The research results provide references for further enriching and perfecting the damage theory of phosphogypsum-based cementitious materials.

The purpose of this study is to improve the resource utilization rate of flue gas desulfurization gypsum, and to explore the effect of flue gas desulfurization gypsum content on the hydration characteristics of supersulfated cement co-activated with calcium aluminate and carbide slag. The effect of flue gas desulfurization gypsum on the hydration mechanism and performance evolution of supersulfate cement was revealed by mechanical property test, hydration product analysis and microstructure characterization. The results show that the compressive strength of supersulfated cement continues to increase with the increase of flue gas desulfurization gypsum content. When the flue gas desulfurization gypsum content increases to 20% (mass fraction), the compressive strength reaches the maximum value. In the early hydration stage, flue gas desulfurized gypsum reacts rapidly with calcium aluminate to form ettringite. Carbide slag provides an alkaline environment, promotes the dissolution of slag, and accelerates the reaction of slag and flue gas desulfurized gypsum to form a large amount of ettringite. At the same time, the formation of hydration products such as calcium silicate hydrate and hydrotalcite accelerates the development of early strength in coordination with the above reactions. In the later hydration, with the gradual consumption of flue gas desulfurized gypsum, the formation rate of ettringite decreases, and calcium silicate hydrate gradually transforms into the main hydration product, continuously improving the strength of matrix.

Reaction-sintering is a common process for the preparation of SiC ceramics, and the prepared SiC ceramics not only have superior performance and low sintering temperature, but also the shape and size of sample are not limited, which have a wide range of application prospects. However, The reaction-sintering SiC remains a lot of residual silicon, which seriously affects the high-temperature performance of material. In this study, the addition of Al2O3-Y2O3-SiO2 sintering additive was used to reduce the residual silicon content. SEM, EDS, TEM and other analytical methods were used to study the effect of sintering additive on the structure and properties of reaction-sintering SiC ceramics. The results show that the sintering additive can effectively fill the grain boundary pores and improve the material properties. When the addition contnet is 1.5% (mass fraction), the fracture toughness and bending strength of sample reach 3.28 MPa·m1/2 and 135.20 MPa. At the same time, the hardness and thermal conductivity also increase to 18.1 GPa and 18.60 W/(m·K). In addition, the presence of alumina and other phases in the sintering aids can effectively improve the stability of SiO2 oxide film and reduce the oxidation rate, thereby avoiding film cracking and significantly improving high-temperature performance of SiC ceramics.

Aluminum titanate (Al2TiO5) is widely utilized in refractory materials due to its high melting point, low thermal expansion coefficient, and exceptional thermal shock resistance. However, the poor sintering densification of Al2TiO5 limits its broader application. In this paper, dense Al2TiO5 ceramics were prepared by spark plasma sintering (SPS), and the effects of SPS and pressureless sintering on the densification of Al2TiO5 ceramics were compared. The results indicate that Al2TiO5 ceramics prepared via SPS exhibit the highest density at 1 350 ℃, 60 MPa and 10 min sintering condition. Compared to pressureless sintering, the apparent porosity of Al2TiO5 ceramics prepared by SPS decreases from (11.34±0.53)% to (2.41±0.61)%. Additionally, the bulk density increases from (3.09±0.01) g/cm3 to (3.64±0.02) g/cm3, and the relative density improves from (83.97±0.22)% to (97.85±0.43)%.

In this study, a foamed ceramics with excellent thermal insulation properties was prepared by high-temperature foaming method using gangue solid waste and feldspar as the main raw materials, MnO2 as the blowing agent and Na2B4O7 as the flux. The effects of sintering temperature, Na2B4O7 addition and sintering time on the performance of foamed ceramics were experimentally investigated. The results indicate that when the sintering temperature is 1 180 ℃ and the sintering time is 30 min, the prepared foamed ceramics exhibit better overall properties, including lower density, higher porosity, and improved thermal insulation. Further exploration of the foaming mechanism of MnO2 as a blowing agent reveals that the oxygen generated from the thermal decomposition of MnO2 at high temperatures effectively promotes pore formation, enhancing the porosity and thermal insulation properties of the foamed ceramics. Additionally, the foamed ceramics not only improves the resource utilization of gangue but also reduces the environmental impact of waste, offering lower production costs and significant potential for energy savings and consumption reduction.

An oxide composite hydrogen barrier coating was fabricated on 316L stainless steel via the sintering method, mainly composed of -Al2O3/Cr2O3/SiO2. The influences of sintering temperature and slurry mass ratio on the macroscopic morphology of the coating were investigated. The microstructure analysis, hydrogen barrier performance, and thermal shock resistance of the coating were also examined. The findings reveal that when the sintering temperature is 725 ℃, and the slurry mass ratio is 1∶5, the surface of the coating is smooth, the number of pores and cracks is small, and the morphology is uniform, with an average thickness of approximately 64 m. The composition phases of the coating are -Al2O3, Cr2O3, and SiO2, in which -Al2O3 and SiO2 are layered and unevenly distributed within the coating, while Cr2O3 is uniformly distributed in the coating. The obtained oxide composite hydrogen barrier coating exhibits excellent hydrogen barrier performance, with a reduction factor 15.3 compared to 316L stainless steel, and capable of withstanding 20 times thermal cycles at 450 ℃.

Samples were prepared based on the chemical composition of Ru porcelain celadon glaze unearthed from Qingliangsi site. High-temperature microscopy, scanning electron microscopy, and colorimeter were employed to study the influence of calcium/potassium molar ratio in the glazes on firing temperature range, microstructure and coloration. The results show that chromatic a* value and gloss of the glazes first decrease and then increase, while b* value does the opposite with calcium/potassium molar ratio decreased gradually from 8.70 to 3.45. When calcium/potassium molar ratio is 5.08, the glaze characteristic shows a sudden change, showing a semi-matte surface, and the color is similar to that of unearthed samples. The microstructures are mainly the changes of morphology of anorthite and phase separation. When calcium/potassium molar ratio is in the range of 8.70~6.47, the morphology of anorthite is columnar, acicular and lamellar, and the phase separation structure gradually changes from isolated droplet to cotton wool, and the average size decreases. When calcium/potassium molar ratio is in the range of 5.08~3.45, the surface tension of the glaze melt begins to fluctuate greatly, the form of dendrite begins to appear, and the secondary branches appear, which decreases the “clarity” of the glaze. When the firing temperature is below 1 170 ℃, glaze with calcium/potassium molar ratio of 8.70 exhibits good melting effect due to its lower softening temperature, while the other samples show poor melting effect due to their higher softening temperature. When the firing temperature is between 1 170 ℃ and 1 220 ℃, glaze with calcium/potassium molar ratio of 5.08 has a relatively wide firing range, with a relatively large amount of liquid phase and changing smoothly. The color is relatively stable and glaze has a good melting effect, which can improve the color fluctuation issue in Ru porcelain celadon glaze caused by the narrow firing range.

In the field of nuclear waste vitrification, Joule-heated ceramic melters (JHCM) is widely employed for the treatment of high-level liquid waste (HLLW) due to their mature technology, high throughput, and suitability for remote operation. In this study, with the aid of the GFM glass furnace model, the operating status of a certain ceramic melter for high-level liquid waste vitrification under different bubbling rates and different bubbling positions was analyzed. The distribution information of each physical field in the melting pool was obtained, and the influence of bubbling rate and bubbling position on the mass and heat transfer of the furnace and the melting rate of the feed was evaluated. The results indicate that as the bubbling rate increases, the average temperature at the cold cap bottom rises slightly, and the scouring velocity at the bottom increases. Lowering the position of the bubbling nozzle expands the circulation region of the flow field, thereby improving the uniformity of temperature distribution within the melter. This study simulates the influence of different bubbling processes on the melting performance of ceramic melter for high level liquid waste vitrification, with the aim of providing technical support for efficient nuclear waste management.

Thin-chamber insulating glazing (TC-IG) possesses a typical double cavity structure, and the influencing factors of its load-bearing deformation performance are more complex. Moreover, the deformation and strength of middle glass also exhibits the significant thickness effects. In this paper, ABAQUS finite element analysis software was used to build a solid modeling of TC-IG, and the effects of glass thickness and wind load on the displacement, maximum principal stress and load distribution ratio of TC-IG under wind load are studied. The results show that the maximum displacement of each piece glass of TC-IG locates at the center of the plate and decreases uniformly around the glass under wind load. With the thickness of middle glass decreases, the maximum displacements of the outer and inner glasses increase, and the maximum displacement of the middle glass first increases and then decreases. The maximum principal stress of the middle glass is lower than that of the outer and inner glasses. With the thickness of the middle glass decreases, the maximum principal stress of the outer and inner glasses increases, while the maximum principal stress of the middle glass decreases. With the wind load increase, the maximum principal stress of the middle glass is shifted from the center of the plate and nearby positions to the four corner positions. The thinner the thickness of the middle glass is, the closer the maximum value of the maximum principal stress is to the four corner positions, which may become the starting point of fracture of the middle glass under high wind load. The wind load distribution ratio of each piece glass of TC-IG is mainly related to the thickness of the middle glass. When the thickness of the outer and inner glass is constant, the thinner the thickness of the middle glass is, the lower the load distribution ratio is, and the outer and inner glass become the main part of the wind load.

Analyzing the interface reaction and thermal stress distribution between materials and slag, the damage mechanism of MgO-CaO refractory in the air gun area of the argon oxygen decarburization furnace (AOD furnace) was investigated. The study of the interface reaction between MgO-CaO refractories and slag finds that the slag preferentially reacts with CaO in the material to form tricalcium silicate (C3S) and dicalcium silicate (C2S). Meanwhile, the dissolution rate of these two products into the slag is much larger than that of MgO and CaO, which is prone to producing liquid. The study of the thermal stress distribution in the air gun area finds that when the hot face of the air gun brick reaches 1 730 ℃ and the average temperature of the cold face is 150 ℃, the introduction of cold airflow creates a great temperature gradient within the MgO-CaO refractory in the air gun area. This causes the maximum thermo-mechanical stresses in the material at a depth of 8 mm from the hot surface. Based on the interface reaction and thermal stress distribution results, it can be inferred that the MgO-CaO refractory in the air gun area bears the maximum thermal stress at a distance of 8 mm from the hot surface during high-temperature service. This leads to stress concentration and crack formation in this area. At the same time, the C3S and C2S generated by the interface reaction between slag and refractory quickly dissolve into the slag, significantly reducing the high-temperature strength of the material. Under the combined action of slag erosion and thermal stress accelerate cracks, accelerating structural spalling, which occurs cyclically during the smelting process and ultimately damages MgO-CaO refractory in the air gun area of AOD furnace.

MgO slurry was prepared by using light-burnt MgO as raw material and aluminum lactate, magnesium lactate and calcium lactate as additives. The hydration process of MgO was systematically characterized by hydration heat test and ionic conductivity analysis. The effects of different lactate salts on the setting time, microstructure of hydration products and hardening strength of MgO paste were studied. The results show that lactate significantly inhibits the hydration process of MgO in the early stage, but has little effect on the hydration process in the later stage. The introduction of lactate not only prolongs the setting time of MgO paste, but also improves the hardening strength of MgO paste. The hardening strength of the sample with aluminum lactate is 24% higher than that of the sample without admixture. Lactate has a significant effect on the microscopic morphology of MgO hydration products. The hydration products of the samples with aluminum lactate show irregular petal-like structure with large specific surface area. The hydration products of the samples with magnesium lactate show regular and interlaced petal-like structure, while the hydration products of the samples with calcium lactate show spherical petal-like structure.

Cement stabilized macadam is the most commonly used material for pavement base. Basalt fiber can enhance the mechanical properties of cement stabilized macadam to different extents. In view of the content of fine aggregate below 4.75 mm is large in cement stabilized macadam with suspended dense structure, the effects of length and content of basalt fiber on the compressive strength and rupture strength of cement stabilized fine aggregate were studied firstly. Based on this, the overall mechanical properties of cement stabilized macadam with basalt fiber and ordinary cement stabilized macadam were compared. The results indicate that the compressive strength and rupture strength of cement stabilized fine aggregate reach highest when the content of fiber with different lengths is 1.2‰ (mass fraction). The fiber content of 1.2‰ in cement stabilized fine aggregate is equivalent to the fiber content of 0.48‰ in cement stabilized macadam. After mixing the fiber of different lengths at content of 0.48‰ into the cement stabilized macadam, it is found that the cement stabilized macadam with 12 mm fiber shows higher unconfined compressive strength and splitting strength. The 28 d unconfined compressive strength, 7 d splitting strength and 14 d flexural-tensile strength of cement stabilized macadam with suspended dense structure increase respectively by 23.4%, 34.2% and 34.1% at the fiber length of 12 mm and content of 0.48‰. In addition, basalt fiber reduces the compressive resilience modulus of cement stabilized macadam, and the reduction rate reaches 22.1% at 14 d.