It is imperative for the cement industry to reduce carbon emission in the context of Chinese active promotion of carbon peak and carbon neutrality goals. A large volume of mineral admixture is used in large volume mineral admixture concretewhich greatly reduces the amount of cementso it has attracted great attention. In this paperthe carbonation behavior and microscopic mechanism of concrete with large volume of mineral admixtureand the influences of common mineral admixtures on concrete carbonation resistance were reviewed. The influence factors on carbonation of cementthe test and evaluation methods of carbonation behavior and their advantages and disadvantages were summarized. Finallythe possible ways of carbonation were proposed and the further research direction was pointed outwhich is of great significance for improving the durability of concrete with large volume of mineral admixture and reducing the carbon emission of the construction industry.

The macroscopic mechanical properties of fiber reinforced concrete are closely related to the interfacial bonding of fiber/matrix. In this paperthe effect of graphene oxide (GO) on the interfacial bonding of polyvinyl alcohol fiber (PVA)/matrix was studied by molecular dynamics simulation. The results show that when GO and PVA fiber are connected by covalent bondthe tensile force required for PVA fiber to be pulled out from concrete is the largestand the presence of GO can improve the interfacial bonding performance between fiber and matrix. The concrete matrix and GO are mainly connected by calcium-oxygen bonds and hydrogen bondsin which the number of calcium-oxygen bonds is large and the strength of chemical bonds is high. Howeverwhen GO and PVA fiber are physically connectedGO and PVA fiber are only connected by weak hydrogen bondswhich has a negative effect on the bonding performance of interface. In additionGO is bound by more ionic bonds and hydrogen bondsthe atomic translational motion is reducedand the interfacial bonding performance with matrix is improved.

In order to study the effect of limestone powder fineness and dosage on the rheological properties and hydration process of cement pastethe rheological properties of freshly mixed paste were tested by Anton Paar rheometerand the thixotropy of paste was characterized by calculating the thixotropic annulus area. Meanwhilethe mechanism of the influence of limestone powder on the rheological behavior of cement paste was explained by using the results of wet stacking density test and the calculation of the thickness of water film powder on the rheological behavior of cement paste was clarified by microcalorimetry test and quantitative analysis. Finallythe influence of limestone powder on the hydration process of cement was clarified by microcalorimetric test and XRD quantitative analysis. The results show thatat 10% dosagethe doping of 1 000 mesh (525 μm) stone powder reduces the yield stress by 48.4% compared with that of 400 mesh (1734 μm) stone powderbut it improves by 15.6% compared with that of 600 mesh stone powder. At the same finenessthe doping of 10% and 20% 600 mesh (1123 μm) stone powder reduces the yield stress of the paste by 76.7% and 81.8% compared with that of the blank grouprespectively. Doping stone powder reduces the thixotropic behavior of paste and changes the variation rule of thixotropy with time. Increasing the fineness and dosage of stone powder increases the wet packing density of pasteand the thickness of water film layerresulting in a decrease in yield stress and consistency of slurry. Increasing the fineness of stone powder can shorten the hydration induction periodmove the second exothermic peak of hydration forwardand promote the early dissolution of C3S and the generation of C-S-Hwhich can accelerate the hydration process of cement.

In order to improve the economic applicability of engineered cementitious composites (ECC) and ensure its good tensile ductilitythe preparation method of PVA-ECC was studiedand PVA-ECC with high cost performance was prepared to provide more material selection for practical engineering. Firstlybased on the micro-mechanical model and multi-scale structural characteristics of ECCthe optimization direction of ECC mix ratio was determined. Thenthe uniaxial compression test and uniaxial tensile test were carried out by designing 12 groups of ECC specimens with different mix ratios. The effects of silica fumecement -fly ash ratiowater-binder ratioPVA fiber type and CaCO3 whisker on the mechanical properties of ECC were studiedand the optimal mix ratio of hybrid fiber cement-based composites was determined. Finallythe economic value of the hybrid fiber engineered cementitious composites prepared in this paper was compared and analyzed by the value engineering method. According to its cost and performancethree representative mix ratios were proposed: H12 with low costrelatively low tensile ductility and reinforced by domestic PVA fibersH11 with moderate costrelatively high tensile ductility and reinforced by hybrid PVA fibers and H8 with high costhigh tensile ductility and reinforced by Japanese PVA fibers and CaCO3 whisker. This study can provide data reference for achieving the dual goals of mechanical performance optimization and economic improvement.

Due to the high cost of fiber reinforced ductile cement-based composites (ECC)it has not been promoted in practical engineering applications. Steel fiber was added to the traditional ECC systemand Nissan PVA fiber was replaced by domestic PVA fiber according to different volume fraction (0%25%50%75%100%) to prepare cost-effective steel-PVA hybrid fiber reinforced ductile cement-based composites. The uniaxial compressive mechanical properties of hybrid fiber reinforced ductile cement-based composites were studied by cube axial compressive test. The results show that with the increase of domestic PVA fiberthe compressive strength of steel-PVA hybrid fiber cement-based composites decreases first and then increasesand the compressive toughness index increases first and then decreaseswhile the peak strain increases significantly. Compared with ordinary cement-based materialssteel-PVA hybrid fiber cement-based composites have better integrity and ductility. Based on the compressive properties and material cost of the compositesthe domestic PVA fiber can replace the Nissan PVA fiber to configure the steel-PVA hybrid fiber cement-based composites to maximize the functional value and economic value.

High shrinkage is one of the bottlenecks limiting the large-scale engineering application of high performance engineered cementitious composites (HP-ECC). This work alleviated the shrinkage of HP-ECC by introducing superabsorbent polymers (SAP). The effects of different amounts of SAP on the compressive strengthflexural strengthtensile propertiesautogenous shrinkage and dry shrinkage properties of HP-ECC were investigated. Scanning electron microscopy (SEM) was used to observe the changes in fiber surface morphology after stretching of HP-ECC caused by SAP. The results show that the addition of SAP reduces the compressive strength and flexural strength of HP-ECC and alleviates autogenous shrinkage and dry shrinkageand the autogenous shrinkage and dry shrinkage decreases with the increase of SAP content. MoreoverSAP reduces the tensile strength of HP-ECC and increases the tensile strain of HP-ECC. The incorporation of SAP reduces the fracture toughness of the matrixmaking it more prone to microcracksthereby improving the strain hardening behavior and multiple cracking of HP-ECC. It is observed that with the increase of SAP contentthe surface morphology of the fibers as they are pulled out of the matrix becomes smootherindicating a decreasing in fiber matrix interface adhesion.

In order to study the early-age shear bond performance of special mortar for autoclaved lightweight concrete (ALC) panelfour groups of special mortar bonded Z-shaped specimens and one group of ordinary mortar bonded Z-shaped specimens were designed and fabricated. Through single-sided shear tests on these specimensthe shear bond strengthfailure characteristics and load-slip curves of ordinary mortar bonded specimens and special mortar bonded specimens under different curing ages were analyzedAdditionallya shear finite element model of special mortar bonded specimens was established by ABAQUS software. The results show that the early-age bond strength of special mortar is higher and develops more rapidly. After 1 d of curingthe shear bond strength of special mortar is 3.5 times higher than that of ordinary mortar of the same strength grade after 28 d of curing. With the increase of curing agethe shear stiffness and ultimate slip of the bond surface of special mortar increase slightly. Compared with the ordinary mortarthe plastic deformation capacity and the bond strength of the test block-mortar interface of special mortar are significantly improved. The load-slip curve and failure characteristics calculated by finite element are in good agreement with the test resultswhich verifies the effectiveness and reliability of the traction-separation law simulation of the bond behavior of special mortar.

The service performance of seamless expansion joints made of polyurethane (PU) material for bridge structures was studied using full-scale tests and finite element models. Firstthree modified PU materials with different mix ratios were prepared. The initial setting timetensile strengthtear strengthhardnessroad adhesionwater absorption rateresistance to ruttingand aging performance were tested and compared to determine the optimal PU mix ratio for seamless expansion joints for bridges. Thenfour full-scale seamless expansion joint specimens were designed and fabricated using the selected PU materialand a corresponding finite element model was also developed. Finallyby comparing the experimental measurements and the finite element calculationsit is shown that the designed seamless expansion joint exhibits excellent service performance under uniaxial tension/compressionvertical deformationand low-cycle fatigue loading conditions. Additionallythe research results indicate that setting a 45° inclination angle between the modified PU seamless expansion joint and the road surface could significantly improve the stress state and prevent early cracking at the joint.

Vibration is an essential mean of concrete compaction and forming. The effect of vibration directly determines the mechanical properties and durability of hardened concrete. Based on Stokes’ lawthis paper proposed a new method for measuring and evaluating the rheology of fresh concrete under vibrationnamelythe pulling-ball method. The correlation between the rheological parameters obtained by this method and those obtained by the rheometer at static state was analyzeddemonstrating the pulling-ball method’s reliability for evaluating the rheology of fresh concrete. The results show good linear correlations between the plastic viscosity and the yield stress obtained by the pulling-ball method and those obtained by the rheometer individually. Vibration can reduce the viscous drag force of cement mortar near the internal poker vibrator by more than 90% and effectively discharge large bubbles (pore size Φ>500 μm) and retain tiny bubbles (Φ<200 μm). Vibration substantially affects removing large bubbles with increasing air-entrained agent (AEA) content. When the AEA content roses from 0.015% to 0.030% (mass fraction)the decreasing of air void content with the pore size of ［500, 1 000) μm increases from 31.0% to 84.8%and those with the pore size of ［1 000, 2 000) μm increases from 103% to 36.4%.

Taking aeolian sand concrete as research objectthe micro-pore structuremicro-morphology and product characteristics of concrete under different aeolian sand content and different concentration of sulfate erosion were observed by nuclear magnetic resonancefield emission scanning electron microscope and energy spectrometer. The results show that with the increase of aeolian sand contentthe compressive strength of aeolian sand concrete increases first and then decreasesand the porosity decreases first and then increases. When the content of aeolian sand is 40% (mass fraction)the mechanical properties are the best. With the increase of magnesium sulfate concentration and the extension of erosion periodthe relative dynamic elastic modulus of aeolian sand concrete increases first and then decreases. When the concentration of magnesium sulfate is 3.5% and the content of aeolian sand is 40%the aeolian sand concrete still meets the standard requirements after soaking for 360 d. At this timethe porosity of aeolian sand concrete is 2.553%of which the proportion of less harmful and harmful pores reaches 63.8%and more needle-like ettringite is produced. When the concentration of magnesium sulfate is 5.0% (mass fraction)the porosity increases to 2.879%the proportion of less harmful and harmful pores decreases to 57.3%and the enrichment degree of ettringite further increases.

Higher strength and toughness concrete infrastructures are essential for resilient city construction. There are still some challenges in the existing mesoscopic model and fracture performance simulation research of steel fiber reinforced concrete (SFRC). Herewith the secondary development of Abaqus pre-processing method aiding with Python softwarea three-dimensional mesoscopic model of SFRC was establishedand cohesive units were inserted globally to simulate the interface between the aggregate and concrete matrix to study the effects of volume content of steel fiber VSFconcrete matrix strengthand particle size of aggregate on the uniaxial compressive fracture performance of SFRC. Results show that in the range of 0% to 2.0%the larger the VSF isthe superior the rupture resistance of SFRC isand the greater the residual stress is. When VSF is 2.0%the stress of SFRC is 60.64% higher than that of concrete without steel fiber. When the strength of concrete matrix increasesthe maximum stress corresponding to C60 and C80 grade concrete increases by 6648% and 91.39%respectivelycompared with that for C40 grade concretethe toughness of SFRC also increases and the stress-step curve of SFRC becomes steeper in the elastic phase. In the 5~7 mm range of aggregate particle sizethe rupture resistance of SFRC increases significantly with the increase of aggregate particle size. Thereforeit can be concluded that the incorporation of dispersednon-directional ductile steel fiber into a brittle concrete matrix can effectively enhance the seismic toughness and rupture resistance of the corresponding concrete infrastructure.

In order to explore the influence of high temperature on the dynamic and static mechanical properties of steel fiber reinforced self-compacting concrete (SFRSCC)the dynamic and static mechanical properties of SFRSCC at room temperature (25 ℃) and after heat treatment at different temperatures (200400600800 ℃) were testedand the numerical simulation analysis was carried out by combining LS-DYNA software and HJC constitutive model. The results show that the static compressive strength of SFRSCC increases first and then decreases with the increase of temperature gradeand reaches the maximum value of 66.9 MPa at 200 ℃. Under the same level of impact loadwith the increase of temperature gradethe dynamic compressive strength of SFRSCC increases first and then decreasesand reaches the maximum at 200 ℃. The dynamic compressive strength of SFRSCC increases with the impact load leveland the dynamic strength growth factor increases with the increase of strain rate. The failure modes of simulation and test are consistent.

In order to study the influence of straight through pore diameterwater depth and horizontal runoff velocity on the anti-clogging performance of new self-compacting pervious concrete (NSPC)the permeability coefficient of NSPC after blockage and high-pressure water gun flushing was tested. Based on the probability that the blockage is captured by straight through porea NSPC clogging model was established. The results show that the permeability coefficient of NSPC increases with the increase of diameter of straight through pore. When the ratio of straight through pore diameter to blockage particle size is greater than 5the particle flow formed by blockage still causes NSPC blockage. The increase of water depth reduces the permeability coefficient of NSPC after blocking. The horizontal runoff velocity has little effect on permeability coefficient of NSPCbut it delays the time of permeability coefficient reduction. The highest recovery rate of permeability coefficient of NSPC after high pressure water gun flushing reaches 85%. The established NSPC clogging model can predict the variation of the mass of blockage and the attenuation rate of permeability coefficient in straight through pore channel.

Strength prediction method of high performance concrete based on stacking model fusion was proposed to address the issues of large deviations and low efficiency of traditional empirical formulas for high-performance concrete strength prediction. Firstly1 030 sets of high-performance concrete compressive strength test data were preprocessed through data cleaning and normalization to eliminate abnormal data and the dimensional influence among data. Secondlybased on extreme gradient boosting (XGBoost)category boostingmulti-layer perceptronand random forest (RF) algorithmshyperparameter optimizationmodel training and evaluation were conductedand the overall effect of the four base learners on strength prediction were compared and analyzed using coefficient of determination R2root mean square error and mean absolute error. Based on thisa Stacking ensemble learning model was constructedwhich fuses multiple machine learning algorithms for concrete strength prediction. Finallythe model was validated using 103 sets of new dataand interpretable analysis was performed. The results show that compared to other combinations of base learnersthe fusion model using XGBoost and RF significantly improves prediction accuracy and performanceand has good generalization performance. The interpretable analysis shows that the most important input feature variables are age and cementindicating that the internal prediction logic of the model is more in line with engineering practice experiencehaving high rationality and reliability. The research results provide reference for further improving the accuracy of high-performance concrete strength prediction.

Compared with normal rigid concrete pavement overlaythe overlay constructed with ultra-high ductile engineered cementitious composites (ECC) has a longer service life. Life cycle assessment and cost analysis of overlayer made of six typical ECC materials were carried out. The results show that although ECC overlays do not have short-term advantages in terms of environmental impact and costtheir long-term environmental impact and cost are significantly lower than those of normal rigid concrete overlay due to their exceptionally long service life and lower maintenance frequency. Compared with normal rigid concrete overlayECC overlays with supplementary cementitious materials (fly ash or ground granulated blast furnace slag) and environmentally friendly fibers (polypropylene fiber or basalt fiber) reduce the global warming potential by 63.2%~68.5% within a life cyclewhile their costs only account for 9.6%~23.3% of normal concrete overlay.

In order to study the influence of stress level on ultrasonic wave velocity of concreteplain concrete axial tensile specimensplain concrete axial compressive specimensplain concrete cube compressive specimens and reinforced concrete flexural members were designed and poured in this paper. The ultrasonic wave velocity tests of plain concrete specimens and reinforced concrete members under different stress levels were carried out respectively. The results show that the tensile and compressive stress levels have little effect on ultrasonic wave velocity of concrete specimenswhich can be ignored. The low stress level has little effect on ultrasonic wave velocity of reinforced concrete membersand the high stress level has a great influence on ultrasonic wave velocity when cracks appear in concrete members. The tensile stress-ultrasonic wave velocity relationship curves of concrete members can be divided into four stagesincluding no damage perioddamage development perioddamage stability period and component failure period. When the tensile stress reaches 15%～25% of ultimate tensile stressthe component enters damage development period from non-damage periodand the ultrasonic wave velocity does not change at this time. When the tensile stress reaches 35%～55% of ultimate tensile stressthe component enters damage stabilization period from damage development periodand the ultrasonic wave velocity is reduced by about 5%. When the tensile stress reaches 60%～75% of the ultimate tensile stressthe component enters failure period from damage stable periodand the ultrasonic wave velocity is reduced by about 8%.

The use of seashells to replace traditional cement-based materials and study their adsorption capacity for pollutants can expand the functional engineering application range of cement-based materials. This paper first reviewed the principles of adsorption kinetics and adsorption isotherms to demonstrate the adsorption mechanism of seashell materials. Then the effects of pH valuecontact time pollutant concentration and other factors on the adsorption of heavy metal ions and basic dyes to seashells were discussed. Finallythe relevant applications of seashells in the construction field were reviewed. The results show that the experimental use of seashells instead of cementitious materials or natural aggregates in cement-based materials shows good adsorption capacity. The optimal pH value in the process of seashell adsorption is 5~7the active site on the surface of seashell particles is limitedand that it would reach saturation at a certain concentration. The active site of seashell would increase with the decrease of particle sizeso the seashell powder with small particle size is conducive to enhancing the absorption capacity and removal efficiency. By analyzing the adsorption performance of seashell and the applications of seashell in cement-based materialsthis paper could provide ideas and methods for the design of functional cement-based adsorption materials from multiple angles.

Life cycle assessment was used to investigate the environmental impacts associated with the production of slag-calcium sulfoaluminate cement. The main sources of global warming potential (GWP) and primary energy demand (PED) were identified through sensitivity analyses. The CO2 mitigation effect of slag-calcium sulfoaluminate cement relative to Portland cement was further analyzed. The results show that the clinker calcination stage has the highest contribution to GWP and the raw material extraction stage contributes the most to PED in the production of slag-calcium sulfoaluminate cement. Sensitivity analysis shows that the most important factors influencing GWP are limestone and coal contentand the most important factors influencing PED are coal and electricity. Compared with Portland cementslag-calcium sulfoaluminate cement shows a significantly lower GWP and a slightly lower PED. The deficiency on mechanical properties at high slag dosages may hinder the application of slag-calcium sulfoaluminate cement as an alternative to Portland cement.

In order to improve the utilization of industrial waste residuephosphogypsumblast furnace slag and sodium silicate were conducted to replace part of cement stabilize silt. The regression equation of unconfined compressive strength cured for 3 and 7 d was obtained through the D-optimal mixture designand the optimal mass ratio was calculated. The unconfined compressive strength for 3 and 7 d were separately 4.88 and 5.84 MPa by using the optimal formula to solidified soil samples. The microscopic mechanism of solidified soil was studied by X-ray diffraction and scanning electron microscopy. The results show that the hydration reaction of the optimal solidified soil is more complete than that of the cement solidified soilthe connection between the particles is more denseand the structure is more stable. Finallythe environmental and economic evaluation of the optimal formula was carried outand it is concluded that the formula is superior to cement in strengthenvironment and economy.

Neutralization slag (NS) is an industrial waste residue with calcium sulfate as the main component produced by mineral mining and metallurgical treatment processes. The large accumulation and storage of NS will pose a great threat to the environment. Thereforeit is urgent to explore a new technology for recycling NS. The mechanical properties of NS based geopolymers with different granulated blast furnace slag (GBFS) blending levels were investigatedand the phase compositionhydration ratepore structure and micromorphology of the NS geopolymer were characterized by X-ray diffractionreaction heat testingmercury intrusion porosimetryFourier-transform infrared spectroscopy testing and scanning electron microscopy. The results show that the main product of the geopolymerisation between NS and GBFS under the action of activator is C(N)-A-S-H gel. The incorporation of GBFS can increase the rate of polymerization reaction generate more geopolymer gelsmake the microstructure of NS based geopolymer denser and the mechanical properties higher. The 28 d compressive strength of the NS based geopolymer with 30%(mass fraction) granulated blast furnace slag can reach 17.8 MPa.

In order to study the freeze-thaw resistance of iron tailings sand foam concretefive groups of foam concrete with a target density of 900 kg/m3 were prepared. The mass lossstrength losspore area rate and microstructure of foam concrete with different iron tailings sand content after freeze-thaw cycle in sulfate environment were compared and analyzed. Taking the mass loss and strength loss as the measurement indexesthe optimal mix ratio was selectedand the reliability analysis and residual life prediction were carried out based on the Wiener degradation process. The results show that during the sulfate freeze-thaw cyclethe surface of foam concrete is damagedthe internal pores are connected to form cracksand the mass of each specimen increases first and then decreases. The compressive strength and pore area rate continue to declineand the addition of fine iron tailings sand effectively alleviates the damage of foamed concrete. Among themthe foam concrete with 20% (mass fraction) iron tailings sand content has the strongest freeze-thaw resistanceand the specimen fails after about 300 freeze-thaw cycles. This study can provide ideas for the application of foam concrete in frozen soil areas.

With ground granulated blast furnace slag as the main materiala slag-carbide slag based geopolymer was prepared under the excitation of alkaline carbide slag. Through XRDSEMEDSFTIRTG-DSC and other microscopic testing techniquesthe performance and action mechanism of the slag-carbide slag based geopolymer were analyzedand the heavy metal leaching test was carried out for the geopolymer. The results show that when the mass fraction of carbide slag is 14% and the water to cementitious material is 0.34the compressive strength of the slag-carbide slag based geopolymer is 31.8 MPa under the condition of 4 d ambient temperature curing and 32 h steam curing. The hydration products of geopolymer are mainly calcium aluminosilicate hydratecalcium carboaluminate hydrate and a small amount of ettringite crystals. The concentration of heavy metals in the leaching solution meets the national toxicity control standard indicating the safety of geopolymer. Carbide slag has good effect on alkali activation of slag.

In order to improve the utilization rate of solid wastes such as fly ashslagiron tailing sand and manufactured sand and prepare early strength and slightly expansive high-strength grouting material the mechanical properties and microstructure of grouting materials were analyzed under the joint action of solid waste composite materials by mixing ordinary Portland cement and sulphoaluminate cementdesigning the ternary composite system of quartz sandiron tailing sand and manufactured and orthogonal test. The test results show that the optimal mass mix ratio of ordinary Portland cement and sulphoaluminate cement is 4∶1the optimal mass mix ratio of quartz sandiron tailings sandlimestone manufactured sand is 7∶1∶2and the influence degree of four factors on strength of grouting materials from large to small in the orthogonal test is water binder ratiofly ash contentbinder sand ratio and slag content. Through range analysisthe optimal factor level combination is water binder ratio is 0.33binder sand ratio is 1.0∶1.2and the fly ash content and slag content are 6% and 10% (mass fraction)respectively. Through the analysis of XRD and SEMit is found that the density of C-S-H gel will affect the strength of grouting material. The water binder ratio has an effect on the phase of ettringiteand ettringite and tricalcium aluminate hexahydrate can improve the early strength of specimens.

In order to investigate the influence mechanism of various industrial solid waste powders on the mechanical properties and durability of high-performance self-compacting concrete (HPSCC)an experimental investigation was conducted on the concrete with various mass fraction of fly ashfurnace slaglime powdercoal gangue powder and marble powder. The slump flowT50 flow timeL-box and V-funnel flow time were experimentally measured to evaluate the workability of HPSCC. The concrete mechanical properties were evaluated by measuring ultrasonic pulse velocity and compressive strength. In additionthe power consumption and water penetration depth were tested to characterize its durability. The results show that fly ashfurnace slaglime powdercoal gangue powder and marble powder can be used to prepare HPSCC with excellent workability and durability. The allowable mass fraction of fly ash and furnace slag powder is 35% and 60%respectively. Whilethe allowable mass fraction for coal gangue powderlime powder and marble powder is 30%respectively. The addition of fly ash significantly improves the concrete workabilitywith a maximum slump flow of 750 mm. Except for lime powderthe increase of other industrial solid waste powders leads to a better concrete anti-chloride ion permeability. Howeverthe increase of industrial solid waste powders can reduce the impermeability and compressive strength of concrete. The concrete mixed with 30% lime powder shows the largest decrease in compressive strengthwith a reduction of 20.8%.

As a kind of solid wasteflue gas desulfurization (FGD) gypsum can be used to prepare calcined gypsum by calcining at high temperature to realize the resource utilization of solid waste. FGD gypsum was used as raw materialcalcium oxide and aluminum sulfate were added as composite crystal modifiersand calcined gypsum was prepared by calcining at 170 ℃ for 2 h. The effects of the composite ratio and dosage of composite crystal modifiers on the properties of calcined gypsum were studiedand the composite crystal conversion mechanism was revealed. The results show that when the content of composite crystal modifier is 1% (mass fraction) and the composite ratio of calcium oxide and aluminum sulfate is 1∶1 (mass ratio)the prepared calcined gypsum has the best property. The gypsum block is dense after hydrationand the hydration products are in the form of alternating short columns or fibers. The 2 h flexural and compressive strength of calcined gypsum are 3.6 and 9.7 MPathe dry flexural and compressive strength are 68 and 235 MPawhich meets the requirements of grade 3.0 calcined gypsum in Calcined Gypsum (GB/T 9776-2022).

In this paperthe recycling of waste cement is the research goal, a desulphurized gypsum-waste cement system was constructedand the effect of carbonization on the mechanical properties and apparent density of the desulphurized gypsum-waste cement system was evaluated. The compositionchemical structure and morphology changes of the recycled blocks were revealed by XRDFTIR and SEM. The results show that the carbonization of waste cement can proceed smoothly in the presence of gypsum. The carbonization process can effectively improve the compressive strength of desulphurized gypsum-waste cement samples. When the water-cement ratio is 0.4 and the waste cement content is 60% (mass fraction)the compressive strength of carbonized sample increases by 1083% compared with that of the uncarbonized sample. When the water-cement ratio is 0.8 and the waste cement content is 65% (mass fraction)the compressive strength of carbonized sample increases by 270.0% compared with that of the uncarbonized sample. The chemical structure and microstructure of carbonized products can be controlled by adjusting water-cement ratio and waste cement content. The carbonization process can promote the hydration of waste cementenhance the mechanical properties of the systemand reduce the apparent density of the block. The research results will provide a new idea and a reliable recycling scheme for the comprehensive utilization of waste cement and desulphurized gypsum.

To investigate the mechanical properties and microscopic damage evolution of recycled sand/powder concreteABAQUS based on Python language was used to establish a multi-phase three-dimensional finite element model considering virgin aggregateold/new mortar matrix and corresponding interfacial transition zones. The effectiveness of the model was verified by compressive tests on recycled sand/powder concrete samples. The results show that the microscopic model of recycled sand/powder concrete established in this study efficaciously simulates its mechanical properties and microscopic damage circumstances. The discrepancy between the measured and simulated compressive strength is minimalnot exceeding 1065%. The destruction of recycled sand/powder concrete specimen is generally in an “X” shapewhich is fundamentally consistent with experimental phenomenon. The initial damage emerges in interface transition zone and subsequently develops progressively until it penetrates. As the content of recycled fine aggregate and recycled micro powder increasesthe extent of damage expansion becomes more severeand its mechanical properties correspondingly decline.

Construction solid waste can now be recycled and used in a more environmentally friendly manner by utilizing the sand powder created during the process of crushing it into recycled aggregate. This recycled sand powder has beneficial filling and volcanic ash effects. In this studymixed recycled sand powder (recycled composite micronized powderrecycled fine aggregate)and recycled coarse aggregate were produced using discarded bricks and concrete as raw materials. The study examined the effect of mixed recycled sand powder on the durability of cement-stabilized aggregates. The ideal composition of mixed recycled sand powder was determined using the orthogonal test methodalong with indoor compaction testsfreeze-thaw testsand dry shrinkage tests. The influence mechanism of mixed recycled sand powder on the durability of cement-stabilized aggregates was revealed using scanning electron microscope (SEM) in conjunction with energy spectrum analysis. The results show that the compressive strength loss of specimens after freeze-thaw cycle is smaller than that of benchmark specimenwith a maximum decrease of 11.63%and the maximum increase of dry shrinkage strain is 69.75%. Mixed recycled coarse aggregate has the most significant impact on the optimal moisture content and frost resistance of cement-stabilized aggregates. Mixed recycled fine aggregate reduces the deformation resistance of specimen and has a significant effect on its dry shrinkage. Mixed recycled sand powder can effectively improve the density of mixture. The volcanic ash effect reduces the Ca/Si ratio of specimens by 52.83%. Variance analysis identifies that the ideal replacement amount of mixed recycled composite micronized powderrecycled fine aggregateand recycled coarse aggregate is 40%20%and 40% (mass fraction)respectively. These research findings can serve as a guide for recycled materials in the base layer of cement-stabilized aggregates used in road construction.

In order to explore the influences of rubber particles and basalt fibers after interaction and coupling on the mechanical properties of concreteconsidering the three main factors of rubber volume contentbasalt fiber volume content and basalt fiber lengththe influences of these factors on basalt rubber concrete were studied through compressive strengthaxial compressive strengthsplitting tensile strength and flexural strength tests. The results indicate that the increase of rubber content reduces the mechanical properties of concretebut improves its deformation ability and reduces its brittleness. The addition of basalt fibers improves the mechanical strength of concretebut when the content is too highexcept for the tensile strengthall other strength decreases. Comprehensive analysis shows that when the rubber volume content is 10%the basalt fiber volume content is 0.10% and the basalt fiber length is 18 mmthe mechanical properties of concrete are optimal. Based on the analysis of the compressive stress-strain curvesa compressive stress-strain constitutive model for basalt rubber concrete is proposedwhich can be used as a reference for nonlinear analysis and engineering design of basalt rubber concrete components.

In order to explore the resource utilization prospects of municipal solid waste incineration bottom ashthe feasibility of preparing geopolymer from waste incineration bottom ash and tuff was investigated. The effects of bottom ash contentsilicon-sodium molar ratio and alkali equivalent content on the properties of bottom ash-tuff based geopolymer were studied through uniaxial compressive strength testXRDFTIR and SEM. Test results show that the curing time has a great influence on the physical and mechanical properties of bottom ash-stuff based geopolymer. The optimal process parameters of bottom ash-stuff based geopolymer are bottom ash content of 20%the silicon-sodium molar ratio of 1.7 and the alkali equivalent content of 8%. Bottom ash-stuff based geopolymer has a uniaxial compressive strength of 23.2 MPa and bulk density of 1.56 g/cm3 for curing 28 d. The main phases of bottom ash-stuff based geopolymer are quartzsanidineyeelimite and calcite. A large number of aluminosilicate gels are generated during the geopolymerization processresulting in the microscopic structure of bottom ash-stuff based geopolymer shows a binding structure of small and larger particles. Toxicity characteristic leaching procedure of heavy metals in bottom ash-stuff based geopolymer meets the requirements of safety and environmental protection.

In recent yearsthe removal of heavy metal ions is one of the difficult problems faced by water treatment under complex environments. Characterized by high-temperature resistance and strong acid resistancethree-dimensional SiO2 prepared by electrospinning is an ideal precursor material for water treatment in complex environments. SiO2@PEBS nanofiber cotton was prepared by in situ polymerization of ethylene benzenesulfonic acid and diethylbenzene monomer catalyzed by initiator azobisisobutyronitrile on three-dimersional SiO2 nanofiber cotton as the substraterealizing the uniform coating of polyvinylbenzene sulfonate acid on the surface of SiO2 nanofiber cotton. The morphology and chemical composition of SiO2@PEBS nanofiber cotton were revealed using SEM and FT-IRand the thermal stability of the sample was tested with a thermogravimetric analyzer. The adsorption regeneration performance of nanofiber fiber wool under high temperature and acidic conditions was investigated. The results show that SiO2@PEBS nanofiber cotton has high adsorption capacity on Cu2+Cd2+ and Pb2+. Under pH value of 5.5 and initial ion concentration of 100 mg/Lthe adsorption capacity of Cu2+Cd2+ and Pb2+ is 73.091.0 and 161.0 mg/grespectively. At 80 ℃the adsorption capacity still reaches 81.064.0 and 123.0 mg/grespectively. The adsorption process conforms to pseudo second-order kinetics and Langmuir isothermal adsorptionwith high regeneration performance. After 10 times ion adsorption and desorption cyclesthe capacity retention rates for Cu2+Cd2+ and Pb2+ are 835%811% and 776%respectively.

Compared with traditional metal materialAl2O3 fiber reinforced Al2O3 matrix (Al2O3/Al2O3) composites have become a new generation of thermos-structured composites for aerospace that have attracted much attention from scholars all over the world due to their high specific strengthlow densityhigh temperature resistance and oxidation resistance. This paper introduces the commonly used Al2O3 fibers and their basic propertiessummarizes the frequently used interfacial phases in Al2O3/Al2O3 composites and their influence on performance of compositessummarizes the preparation process of Al2O3/Al2O3 composites and their propertiesand points out the future development trend of this materialaiming to provide a reference for the research of Al2O3/Al2O3 composites in China and promote the widespread application of Al2O3/Al2O3 composites in high-temperature components at the hot side of aerospace industry.

Gold conductor slurry is widely used in low-temperature co-fired ceramics (LTCC) because of the good stability and weldability. The surface morphologyparticle size of gold powder have great impact on the gold conductor paste. With chlorinic acid as the raw materialD-isoreascorbic acid as the reducing agent and acacia senegal as the dispersantthree kinds of spherical gold powder with high purity were prepared by different experimental conditionsand their surface morphologyparticle size and specific surface area were all different. The growth process of gold powder belongs to the seed-mediated growth methodand controlling the Cl- concentration and the pH value of the reaction solution can finally obtain different morphology and particle size. The results show that the specific surface area of three kinds of gold powder are 07400418 and 0447 m2·g-1respectively. The specific surface area of gold powder significantly affects the viscosity of gold paste. Gold conductor paste for LTCC with the viscosity of 326209 and 214 Pa·s are prepared in the same ratio with the three kinds of gold powder as the function phaserespectively. The experimental results show that the gold conductor slurry is prepared from the gold powder made when dissolving chloruric acid in NaOH solution and adjusting the pH value to 2as well as the setting 30%(mass fraction) diethylene glycol ether solution as agent solventwhich has the highest density low square resistance and the highest gold wire bond strength. The square resistance and gold wire bond strength are 1.11 mΩ/□ and 8.66 grespectively. The weldability of all the three kinds of gold conductor paste are better.

The effective utilization of fly ash based porous ceramics can not only reduce the pollution of fly ash to the environment but also show high application value in wastewater treatment and other fields. In this paper porous ceramics with excellent performance were prepared by direct molding sintering method with fly ash as the main raw materialbentonite as the binder and activated carbon as the pore forming agent. The effects of sintering temperature and activated carbon amount on the structures and properties of porous ceramics were studied. The results show that sintering fly ash and bentonite forms the porous ceramic skeletonoxidized activated carbon forms the poresand porous ceramics are formed under their synergetic effects. At the same timewith the increase of sintering temperature and the decrease of activated carbon amountthe apparent porosity and water absorption decreasethe bulk density and compressive strength increase. When the sintering temperature is 1 100 ℃ and the amount of the activated carbon is 60% (mass fraction)the prepared porous ceramics with good comprehensive performance can be prepared. Its apparent porosity is 6175%bulk density is 093 g·cm-3water absorption is 63.48%compressive strength is 4.29 MPa. Moreoverits removal rate is 98.4% and the saturated adsorption capacity is 45.79 mg·g-1 in the Pb2+ solution of 100 mg·L-1.

Gradient refractive index infrared imaging system can greatly reduce the sizeweight and cost of system while maintaining imaging performancewhich is expected to advance the development of infrared imaging system towards lightweight and compactness. Howevercurrently available infrared gradient refractive index optical materials are not accessible. Based on 65GeS2-25In2S3-10CsCl chalcogenide glassa gradient temperature field was used to thermally induce the precipitation of axially gradient-distributed β-In2S3 nanocrystals to produce a gradient refractive index transparent chalcogenide glass-ceramics. The results show that the precipitated β-In2S3 crystals are polycrystalline structures composed of nanocrystals with different crystallographic orientationswith a size of about 25 nmand the size and number of crystals are closely related to gradient temperature field. The gradient refractive index chalcogenide glass-ceramics still maintain good transmission in long-wave infraredand their maximum refractive index difference Δn reaches 0.047 at 10 μm.

Using analytical pure reagents as raw materials to simulate zinc-containing smelting slagglass-ceramics were prepared by melting method. X-ray diffractionscanning electron microscopyand Raman spectroscopy were used as characterization methods, and the effect of different zinc oxide content on the formationcrystallizationphysical and chemical properties of glass-ceramics was explored. The results show that the main crystalline phase of glass-ceramics is cordieriteand the addition of a small amount of zinc oxide (less than 0.5%mole fractionsame as below) can enhance the glass-forming ability. As the zinc oxide content gradually increases (0.5%~20.0%)the integrity of glass network structure deterioratesand the viscosity of glass decreases. The main phase of glass-ceramics is transformed from cordierite to spineland the crystallinity and grain size of glass-ceramics increase. Consequentlythe bulk densityhardness and resistance to acid/alkali corrosion of glass-ceramics also increase. Heavy metal zinc has good curability in glass-ceramicsso the leaching concentration of zinc is much lower than the standard valueand leaching rate tends to be stable. This study provides a reference for the solidification of heavy metals through glass-ceramics.

Ultra-short pulse laser has broad development prospects in the field of glass welding due to its unique advantages of high processing accuracysmall heat affected zone and high efficiency. In practical scenariosglass often needs to enhance itself strength through strengthening to meet the reliability of its application. This article successfully realizes welding between chemically tempered glass using infrared ultra-short pulse laser. By observing the shape of welding spot with microscopethe regression equation of welding powerfrequencyspeed and laser welding joint size was summarizedand the accuracy of regression equation was verified. The results show that under the conditions of welding frequency 500 kHz and welding speed 10 mm/sas the welding power increasesthe mechanical strength of welding chemically tempered glass increases first and then decreases. The maximum shear stress of welding chemically tempered glass can reach 11.09 MPaand the maximum tensile stress can reach 7.10 MPa. During laser weldingthe chemically tempered glass is not only subjected to its own thermal expansion pressure but also superimposed tensile stressso it is easier to cause damage to surrounding area.

Glass ceramics have attracted much attention and been widely applied because of corrosion resistance and high strengthas well as easy forming and unique optical properties. Based on SCI papers about glass ceramics from 2013 to 2022which were divided into two stages of 2013 to 2017 and 2018-2022the visual knowledge maps of author scientific collaboration networks and keyword clustering on glass ceramics were constructed with CiteSpace 6and the author scientific cooperation networksacademic activity and visualization development trend were explored simultaneously. The results show thatresearchers are more concerned on luminescence performancebiological activity and solid-state electrolytes of glass ceramics from 2013 to 2017. From 2018 to 2022in addition to continuous study of biological activity of glass ceramics researchers’ attention has shifted to energy conversion and alkali activation of glass ceramics. After summing up the previous resultswe propose that the antibacterial properties of bioactivehigh transparency luminescent and containing micro/nano crystalline phases of glass ceramics are worthy of further researching.

The development of high-performance thermal insulation materials is of great significance to the development of aviationconstructiontransportation and other fields. Silica (SiO2) fiber has the advantages of low densitylow thermal conductivity and oxidation resistanceand is a kind of thermal insulation material with great development potential. Howeverthe thermal conductivity of SiO2 fiber needs to be further reducedso how to further improve its thermal insulation performance is an important topic. Based on the thermal insulation mechanism of SiO2 fiberthe preparation methods and research status of SiO2 fiber with different morphologies (solidhollowporous) are analyzed in this paper. The research progress of SiO2 fiber composite with organic materialsinorganic materials is aslo summarized. At the same timethe main application fields of thermal insulation materials are briefly described. Finallythe development direction of SiO2 fiber-based thermal insulation materials in the future is prospected.

Using the first-principles theorythe electronic structures and magnetic properties of S vacancies (VS) and Tc-doped monolayer MoS2 were investigated. Results reveal that the Tc-doped monolayer MoS2 is a n-type semiconductor with ferromagnetism. Compared with the Tc-doped systemthe introduction of VS does not lead to a significant change in the total magnetic moment of the (TcVS) co-doped systemand the magnetic moment of the doped system is mainly contributed by the Tc atom. In the 2Tc-doped systemthe most stable configuration was determined by formation energy analysis. The magnetic moment of the 2Tc-doped system is 2048 μB and mainly comes from two Tc atoms. The spin charge density analysis shows that the (Tc-4d)-(S-3p)-(Mo-4d)-(S-3p)-(Tc-4d) coupling chain may be the reason for the ferromagnetic coupling of the 2Tc-doped system.