Non-sintered lightweight aggregate (NSLA), also known as cold-bonded lightweight aggregate (CBLA), is a type of lightweight aggregate that does not require sintering and utilizes a large amount of industrial waste, while providing economic, environmental, and social benefits. Current NSLA preparation technologies and product qualities employing a variety of industrial wastes were summarized, as well as curing methods and applications in concrete and other industries. The strategies to reduce density and shell strengthening technologies were highlighted, such as air-introduce, using light raw materials, and employing core-shell construction, with a focus on the challenges of high density, high water absorption, and low specific strength. Furthermore, it is suggseted that the core-shell structure is the development direction for lightweight, high specific strength, and functionalization of NSLA, as well as the pressing issues that must be addressed to achieve lightweight, high-strength, and functionalization of NSLA.

The hydrate phase assemblage and content evolutions of ye’elimite-anhydrite-limestone ternary system were studied based on the thermodynamic modelling. The results show that the evolutions of hydrate phase and pH value can be divided into 5 regions (region Ⅰ~Ⅴ) according to the content of anhydrite and limestone, and the change of pH value of the liquid phase in ye’elimite-anhydrite-limestone ternary system. The boundaries between region Ⅱ and region Ⅲ, Ⅳ are exactly the fully-reaction boundary of limestone. The boundary between region Ⅳ and region Ⅴ is exactly the fully-reaction boundary of anhydrite. The hydration model of ye’elimite-anhydrite-limestone ternary system is established based on the thermodynamic modelling and verified by experimental data. The research results provide an important theoretical basis for the study of the hydration mechanism of ye’elimite-anhydrite-limestone ternary system and the batching design of sulfoaluminate cement.

The conversion of free chloride ions into bound chloride ions in the concrete pore solution can effectively reduce the corrosion of reinforcing steel in reinforced concrete structures in coastal and salt lake areas.The effect of nano-calcium carbonate on chloride ions binding amount of cement stone was investigated. Potentiometric titration was used to determine the content of bound chloride ions, and the chloride ion binding capacity of cement stone was analyzed by plotting the fitted relationship curve between bound and free chloride ions according to chloride ion isothermal adsorption theory. The chloride ion binding mechanism of cement stone was analyzed by XRD and thermogravimetry analysis. The results show that the admixture of nano-calcium carbonate increases the chloride ion binding amount of cement stone, and the total bound chloride ions content is the largest when its admixture reaches 3% (mass fraction). With the increase of chloride ion concentration, the chloride ion binding amount of nano-calcium carbonate doped cement stone increases accordingly. The admixture of nano-calcium carbonate could accelerate the hydration of cement and promote the generation of C-S-H gel and Friedel’s salt, which is beneficial to the chloride ion physical adsorption and chemical binding of cement stone.

Ultra-high performance concrete (UHPC) was designed and prepared by using large substitution level (60%, mass fraction) of limestone and calcined clay instead of cement. Its early hydration behavior and mechanical properties under standard curing and steam curing were studied by compressive strength test, X-ray diffraction (XRD) analysis, isothermal calorimetry analysis and comprehensive thermal analysis. It is found that steam curing significantly improves the loss of compressive strength caused by high cement substitution at 1 d and 3 d, while standard curing brings more excellent compressive strength at 7 d. When the mass ratio of calcined clay to limestone is 2∶1, the strength development of each age is the best. The hydration process is greatly accelerated under the condition of steam curing, and there is an obvious exothermic peak of aluminate phase reaction. Steam curing intensifies the consumption of calcium hydroxide by calcined clay, and the formation of monocarboaluminate is detected only when the mass ratio of calcined clay to limestone is 2∶1, indicating that in the environment of low water to binder ratio, the synergistic effect of early calcined clay and limestone mainly depends on the content of calcined clay.

The large early autogenous shrinkage of ultra-high performance concrete (UHPC) will put the concrete at cracking risk, and adding natural porous active powders to stimulate the synergistic effect of pozzolan and internal curing can effectively reduce the shrinkage deformation and improve the volume stability of UHPC matrix. In this study, UHPC matrix was prepared by replacing cement with calcined diatomite in a certain volume fraction (3%, 6%, 9%), its macro performances such as fresh behaviors, mechanical properties, autogenous shrinkage, durability, and microscopic characteristics such as pore structure and microstructure were investigated. The results show that the incorporation of calcined diatomite significantly improves the mechanical properties and volume stability of UHPC matrix, and further enhances its durability. The pore structure of UHPC matrix with calcined diatomite is optimized, the porosity is reduced and the pore diameter is refined. The average Ca/Si ratio of C-S-H gel in UHPC matrix with calcined diatomite decreases, the proportion of C-S-H (I) increases, and the compactness of hydration products is improved. With the optimized design, the 56 d compressive strength of UHPC matrix increases by 9%, 56 d flexural strength increases by 18%, 7 d autogenous shrinkage decreases by 29%, 28 d rapid chloride ion migration coefficient decreases by 35%, and 28 d electric flux decreases by 27%.

Basalt fiber reinforced polymer bars (BFRP bars) and alkali activated concrete provides a safety guarantee for the durability of concrete in the marine environment. A separate analytical model was proposed to examine the bond slip performance based on a series of pullout experimental tests. Based on the experimental data, the bond slip constitutive model and the plastic damage model of BFRP bars and alkali activated concrete were obtained, and the numerical model based on the nonlinear spring element was constructed. Through the numerical analysis and experimental results, it is concluded that the calculated results of the proposed model matches well with the test results. The test and simulation results show that the specimens with the bond length of 2.5d and 5d (d is the diameter of BFRP bars) all have pull-out failure, while the specimens with the bond length of 10d have splitting failure. The distribution of bond stress between BFRP bars and alkali activated concrete is not uniform. With the increase of bond length and BFRP bars diameter, the ultimate bond strength decreases gradually.When the diameter of BFRP bars is 12 mm and the bond length is 2.5d, 5d and 10d, the ultimate bond strength of alkali activated concrete test block is 13.92 MPa, 13.56 MPa and 12.60 MPa, respectively. Compared with ordinary concrete specimens with the same bond length, the ultimate bond strength increases by 6.58%, 10.97% and 9.76%, respectively.

To study the mechanical properties of rubber concrete under different strain rates, this paper presented an experimental study on rubber concrete under axial loading. The effects of rubber replacement ratio of fine aggregates and strain rate on the mechanical behavior of rubber concrete were analyzed. The test results show that the stress-strain curve and compressive strength of rubber concrete have increasing trend with the strain rate increasing, and the initial damage value of rubber concrete shows a decreasing trend with the strain rate increasing. However, the strain rate has insignificant effect on the elastic modulus of rubber concrete. When the strain rate increases from 3.3×10-5/s to 3.3×10-3/s, the compressive strength of rubber concrete with rubber volume replacement ratios of 0%, 20% and 30% increases by 31%, 24% and 10%, respectively. When the rubber volume replacement rate changes from 0% to 30%, the compressive strength of rubber concrete with strain rates of 3.3×10-5/s, 3.3×10-4/s and 3.3×10-3/s is reduced 17%, 15%, 30%, respectively. The energy consumption of rubber concrete tends to increase as the loading rate increases. Finally, a damage constitutive relationship model of rubber concrete under different strain rates is established based on the experimental data, and the accuracy of the newly established model is verified by the experimental data.

The effects of potassium, sodium, calcium and magnesium four cation types of chloride salt on chloride diffusion properties of fly ash concrete were studied by RCM method and natural diffusion method. Based on molecular dynamics simulation, the radial distribution functions and mean square displacement curves of K+, Na+, Ca2+, Mg2+ and Cl- five types of ions in aqueous solution were analyzed. The results show that the chloride diffusion coefficient of fly ash concrete is mainly affected by the valence state of cations. The higher the valence state is, the greater the diffusion coefficient is. The diffusion coefficient first increases and then decreases with the increase of chloride ion concentration, and the diffusion coefficient first decreases and then increases with the increase of fly ash content. The reason that cation types affect the chloride diffusion property is the different diffusion capacities of ions. The order of hydration capacity of each ion is Mg2+>Ca2+>Na+>K+>Cl-, and the order of self-diffusion coefficient is Mg2+>Ca2+>Cl->K+>Na+. Mg2+ and Cl- in MgCl2 both have corrosive effect on fly ash concrete, and Mg2+ inhibits the excitation of fly ash activity.

Based on the permeability test and scanning electron microscope (SEM) test of textile reinforced concrete (TRC) specimens under pressure water, the effects of different concrete water-cement ratios and fiber number of per bundle on the impermeability and internal mesostructure of TRC specimens were explored. The results show that, moisture migrates along the interface between concrete matrix and longitudinal fiber bundle under pressure water and the impermeability of TRC specimens decreases with the increase of water-cement ratio and fiber number of per bundle. Furthermore, SEM test shows that there are annular cracks at the interface between concrete matrix and fiber bundle, and the crack width increases with the increase of water-cement ratio and fiber number of per bundle. Based on the concentric circular slit theory, the impermeability calculation model of TRC specimen under pressure water is established, and the calculated results are in good agreement with the experimental values.

In order to study the effect of grid size on the tensile performance of basalt textile reinforced concrete (BTRC), BTRC sheets with different grid sizes were subjected to uniaxial tensile tests. The failure modes of BTRC sheets were analyzed from macroscopic and mesoscopic scales. In the analysis process, the ACK model was used to verify the constitutive relation equation of the BTRC sheet tension, and the results were compared and verified by finite element simulation. The results show that BTRC sheets exhibit obvious strain-hardening characteristics under tensile load. The failure mode of BTRC sheets is a typical debonding failure, and the smaller the grid size is, the better the bonding performance between the textile and concrete is, and the more microcracks develop by a single crack. The basalt textile cannot significantly improve the cracking strength of concrete matrix, but can effectively increase the ultimate tensile strength. The smaller the grid size of textile is, the more effective fiber bundles are, and the better the tensile strength is.

Hybrid fiber reinforced roller compacted concrete has been widely used at home and abroad, the ratio of fiber content is one of the main factors affecting its tensile and compression properties. To study the effect of the mix proportion of basalt fiber and coarse polypropylene fiber on the tensile and compression properties of roller compacted concrete, basalt fiber and coarse polypropylene fiber were single doped or hybrid with different proportions into roller compacted concrete. The compressive and splitting tensile tests of fiber reinforced concrete at different curing ages were carried out, the hybrid reinforcing effect of basalt fiber and coarse polypropylene fiber were analyzed. The curing ages were modified based on the maturity theory, and the splitting tensile strength prediction model of basalt-coarse polypropylene fiber roller compacted concrete was optimized. The incorporation of basalt fiber and coarse polypropylene fiber not only improves the compressive and tensile properties of roller compacted concrete, but also optimizes the brittle failure characteristics and improves the toughness of concrete specimens due to the bridging effect of fibers, especially when the mass mixing proportion of basalt fiber and coarse polypropylene fiber is 1∶2, which shows the optimal positive fiber hybridization effect. The compressive strength calculated by the equivalent curing age-compressive strength equation has a better power function relationship with the splitting tensile strength, and the model is convenient to calculate and predict the compressive and tensile properties of basalt-coarse polypropylene fiber reinforced roller compacted concrete at different curing temperatures.

Ultra-high performance pervious concrete (UHPPC) is an indispensable material for heavy-duty road paving in the construction of sponge cities, but insufficient toughness is the main reason why UHPPC heavy-duty paving is easy to crack. In this paper, a novel hybrid fiber-reinforced UHPPC material was prepared by introducing CaCO3 whiskers, PVA fibers and PE fibers, and its compressive strength, water permeability and flexural properties were investigated. It is found that the addition of either PVA fibers or PE fibers improves the compressive strength, flexural strength and ultimate deflection of UHPPC, and the enhancement effect of PVA fibers is better than that of PE fibers. Compared with PVA fibers or PE fibers alone, the hybrid use of CaCO3 whiskers further improves the compressive strength, flexural strength and ultimate deflection of UHPPC. The hybrid blending of PVA fibers with CaCO3 whisker achieves greater improvement in compressive strength, flexural strength, ultimate deflection and flexural cracking pattern than PE fibers blending with CaCO3 whisker. However, the addition of PVA fibers or PE fibers reduces the water permeability coefficient of UHPPC, and the introduction of CaCO3 whiskers further aggravates this reduction effect. Especially the hybrid use of PVA fibers and CaCO3 whiskers in UHPPC, its water permeability coefficient decreases significantly, but still reaches 1.05 mm/s to meet the requirements of engineering application.

Improving the wear resistance of road concrete is beneficial to driving safety and road service life. In this study, the wear resistance of concrete was improved by optimizing particle packing of aggregate. The effects of coarse aggregate gradation, type of fine aggregate, sand ratio, amount of cementitious material, and water-to-cementitious material ratio on the mechanical properties and wear resistance of road concrete were investigated herein. The results show that the wear loss of concrete reduces by 29% when the mass fraction of coarse aggregate with diameter of 16~31.5 mm increases from 25% to 70%. The wear loss of concrete with manufactured sand reduces by 58.3% compared with that with river sand. Higher wear resistance of concrete is achieved by using higher sand ratio. Moreover, reducing the amount of cementitious material and water-to-cementitious material ratio rationally are effective ways to improve the strength and wear resistance of concrete (the abrasion loss is low as (0.320±0.070) kg/m2). The enhancement of bonding between manufactured aggregates and cement paste, which can be attributed to the rough surface and angular of manufactured aggregates, is beneficial to the formation of stable interlocking skeleton. The present investigation provides theoretical foundation and technical support for design and optimization of high wear resistance road concrete.

In order to explore the effects of different lithology and gradations of manufactured sand on concrete properties, the workability and compressive strength of three different lithological manufactured sand concrete and natural river sand concrete were carried out. In addition, the sulfate resistance of four types of concrete under the dry-wet cycle system was compared and analyzed. The results show that the workability of natural river sand concrete is better than that of manufactured sand concrete, and the workability of calcareous manufactured sand concrete is slightly better than that of siliceous manufactured sand concrete. The compressive strength of manufactured sand concrete is better than that of natural river sand concrete and the change trend of mechanical properties of manufactured sand concrete under the action of sulfate attack cycle is basically the same as that of natural river sand concrete. Under the same gradation conditions, the corrosion resistance index of manufactured sand concrete is higher than that of natural river sand concrete; the lithology of manufactured sand does not negatively affect the sulfate resistance of concrete. Well-graded manufactured sand can enhance compressive strength and sulfate resistance of concrete.

The flake particles in manufactured sand (MS) affects the properties of concrete. The effects of the size (1.18~2.36 mm, 2.36~4.75 mm, 4.75~9.50 mm) and the content (10%, 20%, 30%, both are mass fraction) of the flake particles on the fluidity and strength of mortar were studied, and the workability, compressive strength and electrical flux of the concrete prepared from the MS with different content of flake particles were measured. The interface microstructure and pore structure of the MS mortar with different content of flake particles were examined by scanning electron microscope and mercury porosimeter. The results show that with the increase of the content or size of flake particles, the flowability, strength and impermeability of the MS mortar and concrete gradually decrease, and the reduction of flexural strength affected by flake particles from the MS is higher than that of compressive strength. Compared with the regular particles, flake particles weaken the interface transition zone between cement paste and MS particles, and increase the porosity of the mortar and the proportion of large-sized and harmful pores, resulting in the performance degradation of mortar and concrete. Therefore, the content of flake particles in MS, especially the flake coarse sand particles, should be strictly limited.

Electric heat tracing pre-curing is a simple and efficient method to ensure the curing temperature and strength development of ready-mixed concrete in cold weather. The research analyzed the effects of pre-curing temperature and aging on the compressive strength of a high slump C30 normal concrete. Tests of 7 d constant negative temperature (-5 ℃, -10 ℃, -15 ℃) once-freezing to standard curing pretreatment test were reported. According to the definition of critical strength, the reasonable critical strength values and pre-curing time under the electric heat tracing pre-curing treatment were acquired. The results show that concretes pre-cured by electric heat tracing subjected to high temperatures attain higher compressive strengths than concretes subjected to normal temperature. Nevertheless, the pre-curing temperature should be controlled at 30 ℃, because the rate of strength development and R-7+28 (compressive strength of negative temperature curing for 7 d and then standard curing for 28 d) are reduced at higher pre-curing temperatures. When the pre-curing temperature is 30 ℃ and the hardening temperature is not lower than -15 ℃, the pre-curing time is between 36 h and 48 h. Under the hardening condition of constant negative temperature (-5 ℃, -10 ℃, -15 ℃), the critical strength of concrete pre-cured with electric heat tracing is in the range of 6.6 MPa to 17.8 MPa, which is 22.0% to 59.3% of the standard value for the compressive strength of concrete cubes. This paper aims to compare the influence of electric heat tracing pre-curing treatment on the mechanical properties of common concrete and to guide the relevant engineering applications.

Both loading and wet-dry cycle have a key influence on the internal material transport and service life of concrete structures. In order to study the capillary water absorption properties of concrete under the coupled effect of loading and wet-dry cycle, continuous compressive loading at 0%, 10%, 20% and 35% load levels were applied to the concrete specimens, and the changes in the water level in the tube were observed during the 1st, 3rd and 7th wet-dry cycle of water absorption at different load levels, and the cumulative water absorption curves for the first 300 min of the water absorption process were obtained by processing. The results show that the cumulative water absorption of concrete and the water absorption rate at each stage are negatively correlated with the times of wet-dry cycle. When the times of wet-dry cycle are the same, there is a threshold value for the change of the initial water absorption rate S1 of concrete with higher stress level, and the threshold value decreases with more times of wet-dry cycles. The difference between the initial water absorption rate S1 of concrete and the later water absorption rate S2 decreases with more times of wet-dry cycles. The establishment of correlating regression model can well describe the variation trend of concrete capillary water absorption properties under the coupling effect of loading coupled with dry-wet cycle.

Marine concrete is a necessary basic material for ocean development. However, the service life of marine concrete is adversely affected by microbiologically influenced corrosion (MIC). A new type of Ag/TEOS/IBTS composite emulsion (ATS) which can be coated on the concrete surface to prevent MIC was fabricated, characterized and evaluated. Compared with Ag/TEOS composite emulsion (AT) and Ag/IBTS composite emulsion (AS), ATS has the best hydrophobicity among the three emulsions, with a contact angle of 119.67°. Confocal laser scanning microscope (CLSM) results prove that ATS, AT and AS possess good antibacterial adhesion properties, and the silver particles endow the emulsions with excellent bactericidal ability. Results of FT-IR and SEM show that the hydrophobic layer is formed by the cross-linking of Si—O—Si on the surface of the mortar. The new type of coating is meaningful for the service life improvement of marine concrete.

Silica sol grout has advantages of good groutability, controllable gelation time, non-toxicity and high durability, however the compressive strength of silica sol grouted sand is relatively low, which restricts its application. In this paper, a series of single-factor tests were carried out to examine the effects of various factors on the compressive strength of grouted sand. Those factors include the type and concentration of gel-agent, the mass ratio of silica sol to gel-agent and the pH value of grout. In addition, response surface method was used to study the effect of the interaction of the factors including the concentration of gel-agent, the mass ratio of silica sol to gel-agent and the pH value of grout on the compressive strength of grouted sand. The experimental results demonstrate that the following factors are arranged in a descending order in terms of the influencing degree of a single factor, the concentration of gel-agent, the pH value of grout and the mass ratio of silica sol to gel-agent. Moreover, the following factors are arranged in a similar manner regarding interaction effects between two factors, interaction between gel-agent concentration and grout pH value, interaction between gel-agent concentration and the mass ratio of silica sol to gel-agent, and interaction between the mass ratio of silica sol to gel-agent and the pH value of grout. Based on response surface method, the optimized compressive strength of silica sol grouted sand can be achieved when the mass concentration of gel-agent, the mass ratio of silica sol to gel-agent and the pH value of grout are selected as 7%, 7∶1 and 7, respectively. The difference between predicted values of response surface method and experimental measurement is minor, suggesting that response surface method can be used to optimize the proportion of silica sol grout.

In order to utilize the strong alkaline waste mud in commercial concrete mixing plants, the artificial stone was prepared from strong alkaline waste mud of commercial concrete mixing plants simulated in laboratory. The influences and mechanism of metakaolin content and water-cement ratio on the strength of artificial stone were studied in detail. The phase composition and microstructure of artificial stone were analyzed by XRD and SEM. The results show that the addition of metakaolin significantly increases the compressive strength of artificial stone. The compressive strength increases most when the content of metakaolin is 6% (mass fraction), and the strength growth rates at 14 d and 28 d are 18.2% and 20.3%, respectively. The compressive strength of artificial stone increases first and then decreases with the increase of the water-cement ratio. The compressive strength at 14 d and 28 d reaches the maximum when the water-cement ratio is 0.44 and 0.46, reaching 44 MPa and 46 MPa, respectively.

In this study, calcined coal series kaolin with high oil absorption value was prepared from coal series kaolin (Shuozhou, Shanxi province) by using aluminum fluoride trihydrate (AlF3·3H2O) additive which promotes the growth of mullite whiskers and subsequent ultrasonic crushing treatment. The effect of particle morphology on the oil absorption value of the powder was subsequently analyzed. The mechanism of AlF3·3H2O increasing the oil absorption value of calcined coal series kaolin was analyzed by scanning electron microscopy, X-ray diffraction and specific surface area analyser. The results show that the addition of AlF3·3H2O produces a large amount of mullite whiskers on the particle surface of the calcined coal series kaolin, and the submicron mullite whiskers on the particle surface significantly increase the oil absorption value of the samples. In addition, ultrasonic treatment of the samples can further increase their oil absorption values. When the ultrasonic treatment time is 45 min, the oil absorption value reaches 86.14 g/100 g. The circularity of the particles has a great influence on the oil absorption values of the powders. The circularity of the calcined coal series kaolin with high oil absorption values is generally lower than that of the ordinary calcined coal series kaolin, and the distribution of circularity is more concentrated.

The exploitation of combustible gas and the recycle of solid waste are important measures to respond the national policy of low-carbon development and energy transformation. In this paper, ceramic particle proppant was synthesized by the solid waste material of calcined coal gangue for realizing the efficient exploitation of coalbed methane. By adjusting the synthetic conditions, the mechanical properties of the material were finally strengthened for the efficient exploitation of coalbed methane. The experimental results show that the proper addition of calcined coal gangue can effectively adjust the anti-crushing strength of ceramic proppant, and the lowest crushing rate is 3.66% at 42 MPa and 7.97% at 52 MPa, respectively. After the interfacial corrosion treatment of ceramic proppant, it is found that the uniform distribution of Fe element is conducive to the generation of molten liquid in proppant and structural densification. Moreover, the microstructural stress generated by the gap filling of the α-Fe2O3 particle during the process of grain nucleation and growth. The material structure has been strengthened through the dispersive α-Fe2O3 particle, which significantly improves the mechanical properties and crushing resistance of ceramic proppant.

The coal gangue after grinding was added into concrete instead of part of cement, and the coal gangue foam concrete was prepared by physical foaming process. Then, the pore size distribution, average pore size and pore diameter of foam concrete were characterized by FiJi-imageJ image analysis technology. The reasons for improving the porosity of foam concrete by coal gangue and the effect of coal gangue particle size on the compressive strength of foam concrete were analyzed. The results show that when the coal gangue powder with particle size of 45 μm is added, the strength of foam concrete decreases with the increase of coal gangue content, while when the coal gangue powder with particle size of 15 μm is added, the strength increases first and then decreases with the increase of coal gangue content. The coal gangue powder with particle size of 45 μm is better than the coal gangue powder with particle size of 15 μm in adjusting the pore structure, and the optimal effect is achieved at the content of 50% (mass fraction).

To achieve more comprehensive utilization, subway muck was incorporated into expanded polystyrene (EPS) lightweight concrete, and composite sandwich wall panels were prepared with this concrete as the core material. The rheological properties of slurry were studied. Besides, the compressive strength, thermal conductivity and EPS beads areal distribution of EPS concrete were investigated. The results show that the addition of muck slightly increases the yield stress of slurry, but exhibits limited effect on the fluidity. With the increase of muck dosage, the plastic viscosity of slurry increases greatly, contributing to more uniform distribution of EPS. The dry density, compressive strength and thermal conductivity of EPS concrete decrease with the increase of muck dosage. EPS concrete with dry muck to cement mass ratio of 0.8 demonstrates the dry density of 857 kg/m3, the compressive strength of 4.16 MPa and the thermal conductivity of 0.231 W·m-1·K-1. The composite sandwich wall panel (silicon calcium board as panel) with dry muck to cement mass ratio of 0.8 reveals good bonding performance, and the areal density is 81 kg/m2, the compressive strength is 3.75 MPa, the softening coefficient is 0.83 and the fire resistance is greater than 1 h. All indexes meet the performance requirements for the composite sandwich wall panels in Chinese standard.

Based on the ternary cementitious materials composed of cement, fly ash and slag, the mineral admixture metakaolin was added to prepare quaternary cementitious materials. The relationship between hydration products of quaternary cementitious materials and chloride binding capacity was qualitatively analyzed by X-ray diffraction (XRD) and thermogravimetric analysis (TGA/DTG). The content of chloride by chemical binding and physical adsorption was quantitatively analyzed by TGA/DTG and Rietveld’s external standard method. The results show that the addition of metakaolin increases the hydration rate of cement in early stage, and promotes the hydration of fly ash and slag powder, which makes the quaternary cementitious material hydrated to produce more AFm (4CaO·Al2O3·CaSO4·13~19H2O) and C-S-H gel. At the same time, the quaternary hydration system also increases the molar ratio of aluminum to calcium, which makes the monosulfoaluminate more inclined to the conversion of monocarboaluminate in the presence of carbonate. The results of isothermal adsorption of chloride ions show that the content of AFm phase is positively correlated with the binding capacity of chloride ions. The results of Rietveld’s external standard method show that with the addition of metakaolin, the chemical chloride binding capacity of quaternary system is increased, but the physical adsorption capacity of quaternary system is reduced. Compared with the ternary system, the chemical chloride binding capacity increases by 94.16%, and the physical adsorption capacity decreases by 7.62%. TGA/DTG quantitative results show that Rietveld’s method is feasible.

Alkali activated cementitious materials were prepared using lead-zinc tailings as the main materials and adding the supplementary cementitious materials which consist of slag, steel slag, and fluor gypsum. These raw materials were activated by an alkali activator composed of NaOH and sodium silicate. Through orthogonal test, the effects of the modulus of sodium silicate, the content of sodium silicate, and the mass ratio of tailings to supplementary cementitious materials on the mechanical strength of cementitious materials were discussed, and the optimal ratio of raw materials was obtained. Alkali activated cementitious materials based on thermally activated lead-zinc tailings were prepared using tailings that pretreated at 800 ℃, 1 000 ℃, and 1 200 ℃. X-ray diffraction analysis, Fourier infrared spectrometer analysis and scanning electron microscopic analysis were used to characterize tailings and cementitious materials before and after thermal activation. The results show that when the modulus of sodium silicate is 1.8, the mass ratio of sodium silicate is 0.15, and the mass ratio of tailings to supplementary cementitious is 7∶3, the compressive strength of the cementitious material is the highest. The compressive strength of 28 d reaches 20.68 MPa. Inside alkali activated cementitious material exists a generous three-dimensional network structure formed by C-S-H and silicon aluminum polymer which covers the surface of tailings crystal to form a dense matrix providing strength for cementitious materials. When the thermal activation temperature is 1 000 ℃, the compressive strength of cementitious material is enhanced to the greatest extent and the compressive strength of 28 d reaches 28.05 MPa. The internal structure of thermally activated tailings is looser which is conducive to depolymerization of aluminosilicate under alkaline conditions. Meanwhile, more silicon aluminum polymers instead of C-S-H gels were formed, which responsible for higher compressive strength and early hardening characteristics of cementitious materials. The cementitious materials can immobilize Pb and Zn in the internal structure and substantially reduce the leaching of Pb and Zn in tailings. The application of alkali activated cementitious materials may provide a solution to alleviate the harm of heavy metals in tailings to environment.

This paper explores the possibility of using fine iron tailings sand (FIOTS) instead of silica sand (SS) to prepare high-strength alkali-activated mortar (HAAM). Fly ash and slag were used as precursors of alkali-activated materials, the effects of FIOTS/SS mass ratio and curing conditions on the basic mechanical properties of fly ash-slag based HAAM were investigated using MTS universal testing machine, and X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy spectrometry (EDS) were used to reveal the relationship between microscopic phase composition, morphological characteristics and chemical composition of alkali-activated products and macroscopic mechanical properties. The test results show that the compressive strength and splitting strength of HAAM gradually decrease with the increase of FIOTS/SS mass ratio. The highest mechanical properties of HAAM under indoor curing are followed by those under standard curing and under water curing, while the reduction of mechanical properties of the specimens under water curing is more significant with the increase of FIOTS substitution rate. The reduction of mechanical properties of HAAM is mainly due to the inhibition of the alkali-excited reaction process by Fe element in FIOTS, and the formation of mineral phases which are not beneficial to the mechanical properties.

The influence of ultrafine ground granulated blast furnace slag (UFS) and metakaolin (MK) on the chemical shrinkage, autogenous shrinkage and drying shrinkage of calcium sulfoaluminate (CSA)cement were studied. The results indicate that the addition of UFS and MK increases the internal relative humidity of cement paste. The chemical shrinkage, autogenous shrinkage and drying shrinkage of cement paste decrease with the increase of UFS and MK. The autogenous shrinkage can be predicted roughly by the internal relative humidity of cement paste. The incorporation of UFS and MK accelerate the early hydration of cement paste. The time for chemical shrinkage to reach peak value is ahead with the addition of UFS and MK. The autogenous shrinkage and drying shrinkage of the cement paste with 20% (mass fraction, the same below) UFS or 10%, 20% MK are less than that of the control sample. Among them, the autogenous shrinkage of cement paste at 7 d decreases by 42.21%, 35.89% and 63.73%, respectively, and the drying shrinkage at 7 d decreases by 24.89%, 16.42% and 30.87%, respectively. In addition, the pastes with MK show less chemical shrinkage, autogenous shrinkage and drying shrinkage than that of the pastes with the same content of UFS. The proportion of autogenous shrinkage to linear chemical shrinkage decreases with the increase of curing time, and decreases with the incorporation of UFS and MK.

Lithium slag (LS) powder and steel slag (SS) powder were used to partly replace the P·O 42.5 cement (PC) to prepare composite cement pastes. SEM, XRD and FT-IR were used to analyze the effects and mechanism of the two slags on samples. The results show that the replacement of part of cement with LS reduces the fluidity of paste, while the replacement of part of cement with SS is beneficial to improve the fluidity. LS promotes coagulation, while SS slows coagulation in paste. The fluidity and setting time of pastes are controlled by the combined effects of LS and SS. LS has more obvious advantages than SS in improving the mechanical properties of paste. When the water-binder ratio is 0.4, the compressive strength at 28 d of the sample mixed with 20% (mass fraction) LS reaches more than 62.3 MPa, which is about 23% higher than that of control sample. SEM results show that the microstructure of paste with 20% LS is denser than that of control sample at 28 d. XRD results show that the hydration products of the composite pastes are mainly C-S-H gel and calcium hydroxide. FT-IR results show that the peak position of Si—O bond has a red shift, and the H—O—H bond has a blue shift.

In order to promote the resource recycling of industrial waste residues, the industrial waste residues composite cementitious material (RC) and the corresponding foamed lightweight soil was prepared. The composite foaming agent was prepared by mixing rosin resin and protein foaming agents and surfactants by high-speed shear. The optimum process was optimized based on the fluidity, wet density and compressive strength of RC foamed soil with different foaming agents, stirring speed and stirring time. The mechanical properties of RC foamed soil and cement foamed soil were compared based on compressive strength at different wet densities and ages. The durability of RC foamed soil and cement foamed soil was compared based on dry shrinkage test and freeze-thaw cycle test. The composition of RC foamed soil was analyzed by XRD. The results show that the composite foaming agent combines the advantages of good stability of rosin resin foaming agent and high foaming multiple of protein foaming agent. The optimum stirring speed is 200 r/min and the stirring time is 2 min for the preparation of RC foamed soil. The fluidity of the two kinds of foamed soil of RC and cement meet the requirements of the specification, and the initial compressive strength is equivalent.With the increase of age, the growth of RC foamed soil strength is higher than that of cement foamed soil. At 28 d and 56 d, the strength of RC foamed soil is 1.21 times and 1.35 times of the corresponding strength of cement foamed soil respectively.The dry shrinkage and freeze-thaw resistance of RC foamed soil are better than those of cement foamed soil in the same condition. Compared with cement hydration products, RC hydration products contain newly added ettringite and higher content of hydrated calcium silicate.

In this work, (Ti0.25Zr0.25Nb0.25Ta0.25)C high entropy ceramics (HECs) was successfully prepared by spark plasma sintering (SPS) of carbide powder. The microstructure evolution, mechanical properties and oxidation behavior of HECs were systematically studied. The results show that the formation temperature of single-phase HECs is 1 800 ℃, which is below the reported HECs sintering temperature. The ceramic grains sintered at 1 900 ℃ are fine, average grain size is about 7.5 μm, and the element distribution is uniform, with a relative density of 99.2%. The room temperature microhardness of HECs sintered at 1 800 ℃ and 1 900 ℃ is 30.9 GPa and 33.2 GPa, respectively, and the fracture toughness is (4.6±0.24) MPa·m1/2 and (4.5±0.31) MPa·m1/2, respectively, higher than most reported HECs. The results of high-temperature nanoindentation test show that the hardness of HECs decreases with the increase of temperature. When the temperature reaches 500 ℃, the hardness of the ceramics sintered at 1 800 ℃ and 1 900 ℃ decreases to 21.9 GPa and 22.2 GPa, respectively, with outstanding high temperature stability. When the temperature is lower than 500 ℃, there is no obvious oxidation of HECs. When the temperature is higher than 650 ℃, there is obvious oxidation and the oxidation rate increases with the increase of temperature.

BiFeO3-based lead-free piezoelectric ceramics often had poor piezoelectric properties due to large leakage currents. However, the methods of improving its insulating and electrical properties were more complicated, limiting its industrial production and application. In this work, the high insulating and high piezoelectric properties were achieved by simple raw material pretreatment (changing the drying time of Fe2O3 raw material) without component doping and atmosphere sintering of 0.7BiFeO3-0.3BaTiO3 ceramics. The results show that with the increase of the drying time of Fe2O3 raw materials, the grain sizes and insulating of 0.7BiFeO3-0.3BaTiO3 ceramics are significantly improved, and their electrical properties and temperature stability are also significantly enhanced. When the drying time of the raw material is increased to 192 h, the sample grain size is the largest, the insulating is the best, and the piezoelectric properties (d33=203 pC/N, kp=0.33) and Curie temperature (Tc=460 ℃) are also optimal. This provide a new idea for the future study of the piezoelectric properties of BiFeO3-based ceramics.

The surface of silicon nitride (Si3N4) powder was functionally modified by hydroxylation combined with silane coupling agent (KH560) to prepare Si3N4 paste with high solid content and high curing depth. High strength Si3N4 complex structures based on stereolithography (SL) process were fabricated. The results show that KH560 on the surface of Si3N4 improves the compatibility of powder and resin, and reduces the viscosity of Si3N4 paste. At the same time, the epoxy group (—CH(O)CH2) of KH560 is combined with epoxy resin (EA) through chemical bonds or other ways to form an EA core-shell structure, which reduces the refractive index difference between the resin and ceramic particles. Thus, the curing depth of Si3N4 paste is improved. After the surface hydroxylation treatment, more KH560 is adsorbed on the surface of Si3N4, which further reduces the viscosity of Si3N4 paste and increases the curing depth of Si3N4 paste. Finally, the Si3N4 paste prepared with hydroxylated and KH560 modified Si3N4 powder has a solid phase content of 50% (volume fraction) and a curing depth of 64 μm. After sintering, the density of Si3N4 sample is 83%, the fracture toughness is (4.38±0.45) MPa·m1/2, and the flexural strength reaches (407.95±10.50) MPa.

Compared with traditional soda lime silicate glass and high alumina silicate glass, lithium aluminum silicate glass has the characteristics of dense network structure, high elastic modulus, suitable for two-step chemical strengthening and so on. It is regarded as the third generation high strength glass substrate and can be used for the cover plate of electronic information products, aviation transparent parts, observation windows of ships and special vehicles and so on. At present, the research on lithium aluminum silicate glass mainly involves: (1) Exploring relationship among composition, structure and performance so as to provide theoretical guidance and performance prediction for the design and optimization of high-performance lithium aluminum silicate glass. (2) Improving the existing overflow and float forming methods and equipment to realize the preparation of large-size, multi-thickness and high-precision lithium aluminum silicate glass. (3) The two-step chemical strengthening method of lithium aluminum silicate glass is studied to break through the problem of synchronous improvement of surface compressive stress and stress layer depth, and significantly improve the strength, hardness and drop resistance of the glass. The worldwide research progress of lithium aluminum silicate glasses from the three above-mentioned perspectives were summarized.

MgO-C refractories, as key basic materials for iron and steel smelting, are widely used as lining brick of converter furnace, furnace wall of electric arc furnace, and brick of ladle slag line. Therefore, it is of great significance for the development of refractory and metallurgical industry to explore new ways of preparing high-performance low-carbon MgO-C refractories. In order to provide a reference for further promoting the development of low-carbon MgO-C refractories, the research progress of improving the structure and properties of low-carbon MgO-C refractories was reviewed from the aspects of the introduction of nanocarbon sources, the surface modification of aggregates and introduction of magnesium-based aggregates, the modification of phenolic resin, the introduction of antioxidants, and the in-situ formation of ceramic phase. Finally, the future research directions of MgO-C refractories were prospected.

The effects of conventional carbon sources such as pitch, carbon black, coke and graphite, etc., surface modified carbon and new carbon sources on the properties of Al2O3-SiC-C iron trough castable were summarized. It was pointed out that pitch plays an important role in Al2O3-SiC-C castable. After softening by heating, pitch penetrates or volatilizes and condenses into the grains boundary or pores of the castable, which enhances the bonding between grains. Pitch which is uniformly distributed in matrix of castable can improve the liquid phase distribution in matrix and avoid over sintering at high temperature, so as to significantly improve the slag resistance of the castable at high temperature. The particle size of carbon black is very small, which can fully fill the pores, reduce the average pore size of the calcined sample, and improve the corrosion resistance at high temperature. Carbon black, coke and graphite are suitable to be used together with pitch to achieve complementary effects. Granular graphite in surface modified carbon has good application effect, which can introduce more graphite in Al2O3-SiC-C iron trough castable by adding pelletized graphite and significantly improve the slag resistance. Besides, it can also effectively improve the service life of iron trough by adding Carbores P together with pitch to Al2O3-SiC-C castable.

Lithium ion batteries have been widely used in portable electronic devices, electric vehicles and power grids, which have a profound impact on people’s daily life. It is necessary to develop stable and efficient electrochemical energy storage materials due to their low energy density and safety. Clay minerals have great application potential in the construction of lithium battery materials because of their unique nanostructures, rich active sites, high specific surface area, rich reserves and cost-effectiveness. In this paper, the classification, structure and chemical composition of clay mineral were introduced firstly. Then, the application research progress of clay mineral in the separator and solid-state electrolytes of battery was reviewed. Finally, the advantages and disadvantages of clay mineral in the energy-storage systems were discussed, and the future development trend was also prospected.

Zeolite-based slow release fertilizers have broad application prospects in agricultural sustainable development due to many advantages such as nutrient retention, soil amendment, soil moisture retention, environment protection, etc. The research on mechanism and application of zeolite-based slow release fertilizers in recent years was reviewed. It was concluded from slow-release mechanism that the exceptional high cations exchange capacity and strong affinity of zeolites for NH+4 and K+ can be exploited to maximize the nitrogen and potassium use efficiency in agricultural applications. Although almost all of zeolites have no high affinity for anionic fertilizers such as NO-3, PO3-4 and SO2-4, by modifying their surface chemistries using cationic surfactant, multifunctional zeolite adsorbents with capability to trap anions and non-polar organics can be obtained. In addition, controlled available phosphorus is achievable by a combination of zeolite ion exchange and phosphate rock dissolution. The application study showed that factors affecting the performance of zeolite-based slow release fertilizers mainly includes zeolite type and application rate, method of the application, zeolite particle size and density, soil texture and structure, as well as nutrition type and supplies. Based on the current research, it pointed out that the economic evaluation, technological development and application demonstration of zeolite-based slow release fertilizers will be the focus of future research.

The industrial waste cenospheres of fly ash (CFA) were calcined to prepare easily recoverable adsorbent materials. Using trichloroethylene (TCE) as the target pollutant, the feasibility of adsorption and the effects of different modification parameters on the removal of pollutant were investigated. Box-Behnken design (BBD) based on response surface methodology (RSM) was applied to demonstrate the effect of the interaction of calcination temperature, calcination time and particle size on the adsorption of TCE. X-ray diffraction (XRD), Scanning electron microscope and energy dispersive spectrometer (SEM-EDS), Brunner-Emmet-Teller (BET) were employed to explore the adsorption properties of materials. The results show that the surface of CFA after calcination modification is loose and porous, resulting in the increase of specific surface area by about 2.4 times. The order of factors affecting the adsorption of TCE by modified CFA is as follows: calcination time > calcination temperature > particle size. The optimum conditions are confirmed as follows: the particle size is 0.25~0.38 mm, the calcination temperature is 640 ℃ and the calcination time is 80 min. The adsorption value of CFA is 1 344 μg/g under the optimum conditions, with the difference of 1.4% compared with the predicted adsorption of 1 326 μg/g. CFA modified by high temperature calcination have better adsorption properties, which is a kind of environmental protection material that can be easy for mass production, waste utilization and recycled.

In order to improve the permeability of the soil-bentonite (SB) isolation barrier and its adsorption effect on phenol, a polyacrylamide modified soil-bentonite (PSB) was prepared. The effects of polyacrylamide content, phenol concentration, dry-wet cycles and freeze-thaw cycles on the permeability coefficient of PSB isolation barrier and the adsorption effect on phenol were studied, and the mechanism of these effects were revealed at micro level. The results show that phenol concentration has no effect on permeability coefficient of PSB isolation barrier. The permeability coefficient of PSB isolation barrier increases under dry-wet cycles but remains the same order of magnitude. The permeability coefficient of PSB isolation barrier increases by 1~2 orders under freeze-thaw cycles. Polyacrylamide reduces the permeability coefficient of PSB isolation barrier under dry-wet cycles and freeze-thaw cycles, indicating that it can effectively restrain the destructive effects of dry-wet cycles and freez-thaw cycles. The adsorption rate of phenol on the PSB isolation barrier with 0.7% (mass fraction) polyacrylamide reaches over 69%, which is about 50% higher than that on the SB barrier, and gradually increases with the increase of concentration of phenol contaminated solution. The research can provide theoretical basis and parameter support for isolation and closure of phenol pollution.

If diatomite is made into diatomite/molecular sieve composites, its specific surface area and adsorption capacity will be significantly improved. In this paper, diatomite/aluminum phosphate molecular sieve composites were prepared by a series of combined treatment processes of washing, sintering and acid hydrothermal treatment, and the feasibility of forming aluminum phosphate molecular sieve was verified by adding aluminum source, and the microstructure evolution behavior and pore structure change law during the formation of high-quality diatomite were discussed. The results show that the pore structure of diatomite includes macroporous, mesoporous and a small amount of microporous structure. Sintering at 500 ℃ dredge the holes of diatomite shell, but too high sintering temperature lead to the collapse of tubular structure. The aluminum phosphate molecular sieves with mesoporous structure are synthesized by acidic hydrothermal treatment. With the addition of aluminum source, the content of aluminum phosphate molecular sieves in diatomite/molecular sieve composites increases. When the aluminum source is 1.5 times of aluminum content in diatomite, the specific surface area and adsorption performance reach the maximum.