The durability problem caused by environmental erosion factors is an important reason that restricts the long-term service of reinforced concrete structures. Among them, the corrosion of steel bar caused by chloride erosion is one of the main factors causing the durability problem. The addition of anti-corrosion additives can improve the rust resistance by promoting film formation on the surface of steel bar and improving the properties of concrete (pore structure, hydration process, Friedel’s salt generation), which has gradually become a research hotspot in recent years. In this paper, the anti-corrosion additives were divided into four categories: traditional corrosion inhibitor, green plant extract corrosion inhibitor, nano materials and mineral admixtures. The research on anti-corrosion additives was reviewed from the aspects of material development, action mechanism and influence factors of corrosion inhibition. Finally, the shortcomings in the research of anti-corrosion additives were analyzed, and the suggestions for future research were put forward, in order to provide a reference for the prevention and control of steel bar corrosion in concrete.

Concrete canvas (CC) offers the benefits of being soft and simple to lay, not requiring vibration mixing or formwork support during construction, hardening quickly, and not requiring heavy equipment. Since CC emerged, it has garnered much attention and extensively studied. This paper systematically reviewed the research progress on CC in two aspects: (1) The influences of cement types, water-cement ratio and space structure of 3D spacer fabric on the mechanical properties of CC were summarized. (2) The application scenarios of CC and material properties were summarized. These conclusions provide important references for further research on the application of CC.

Ettringite is one of the key hydration products of cementitious materials such as sulphoaluminate cement, common Portland cement and other clinker-free cement. Its crystal structure consists of a central column and grooves parallel to the central column. The hexagonal groove structure is around the central column and sulfate and water molecules connect in the grooves by a network of hydrogen bonds that keep the ettringite structure. In the hydration reaction of cementitious materials, ettringite crystals are easily affected by external factors. Among them, external factors such as supersaturation of reactant ions, temperature, water reducing agents, chloride ions and seed crystal often change the number of water molecules and hydrogen bonds of ettringite crystal structure, which in turn changes the stability of crystal structure as well as morphology. In addition, in the process of synthesizing ettringite crystal, the stirring paddle type and rotational speed also affect the crystal structure and morphology of ettringite, resulting in cognitive inconsistency. Based on a systematic review of the crystal structure of ettringite, the influences of various external factors on its structure and morphology in detail were summarized, various research methods were introduced, and some research suggestions on the crystal formation and morphology of ettringite were proposed.

The rheological properties of cement paste are not only related to its proportion, but also influenced by the environmental effects. In this paper, considering the main external effect factors existed in the actual engineering of cement-based materials, the influences of temperature and shear rate on the rheology of cement paste with low water-to-binder ratio were investigated. The results show that the rheological properties of cement paste are related to the pre-shearing before data logging, the yield stress decreases and shear-thickening intensity increases with the increasing pre-shearing rate. The superplasticizer adsorption on cement particles increases and the apparent viscosity at equilibrium decreases with the elevating temperature. Besides, the effects of temperature and shear rate on the equilibrium apparent viscosity of cement paste have a coupling effect. The higher the shear rate, the smaller the effect of temperature, and vice versa. The mathematical relationship of equilibrium apparent viscosity under different temperatures and shear rates is established.

In this paper, the MgO with different reactivity was prepared by the secondary constant temperature calcination of the raw material light burned magnesium oxide powder for 1.5 h at different temperatures. The setting time, fluidity, compressive strength and reaction solution pH value of a new type of magnesium silicate hydrate cement cementitious materials (also known as magnesium silicate phosphate hydrate cement, MSPHC) prepared with different reactivity MgO, silica fume (SF) and dipotassium hydrogen phosphate (K2HPO4) were investigated. The mechanism was analyzed through X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG) and scanning electron microscopy (SEM). The results show that with the increase of calcination temperature, the intensity of MgO diffraction peak increases and the reactivity decreases. The faster the setting time and poorer the fluidity of the MSPHC purified slurry prepared by MgO with higher reactivity, while the MSPHC prepared with moderate reactivity MgO can achieve better mechanical properties. The most important hydration product of MSPHC is magnesium silicate hydrate (M-S-H) gel, besides, Mg(OH)2 and MgKPO4·6H2O (MKP) are also generated. The MgCO3 component in the raw material light burned magnesium oxide powder does not participate in the system reaction. MSPHC prepared by MgO with moderate activity has the highest hydration product M-S-H gel generation within 28 d of age, so the hardened body has the highest compressive strength. The higher the reactivity of MgO in the MSPHC reaction system is, the faster the dissolution rate is, the faster the hydration reaction process is.

In order to study the effect of single-doped cement and composite curing agent (composed of cement, raw basalt fiber, lime and raw plaster) on the static characteristics of plateau lacustrine peat soil in the Dianchi Lake area, a static triaxial non-consolidation and non-drainage shear test was carried out on cement improved soil and composite curing agent improved soil at different dosage levels, and the triaxial stress strain relationship and shear strength change law of the two improved soils were studied. The results show that with the increase of the dosage, the peak strength of the main stress difference between the two improved soils increases. When the mass fraction of the composite curing agent is 15%, compared with the two doping levels of 5% and 10%, the triaxial stress-strain relationship of the compound curing agent modified soil is changed from “strain hardening type” to “strain softening type”, and the shear strength is significantly improved. When the internal structure of the improved soil is damaged, the shear strength of the cement improved soil has a large loss, while the composite curing agent improved soil still maintains a high shear strength.

The alkali activated slag foamed concrete (AASFC) was prepared by chemical foaming method with hydrogen peroxide as foaming agent and water glass as activator. The effects of initial temperature of activator, dosage of catalyst, type of foam stabilizer and pore structure on the basic mechanical properties of AASFC were studied. The results show that by adjusting the initial temperature of activator and the dosage of catalyst, a good balance can be achieved between the gas generation rate and slurry setting and hardening. The AASFC with density of about 250 kg/m3 and good internal structure is successfully prepared by adding appropriate foam stabilizer. Comparing the compressive strength of AASFC prepared with different foam stabilizers at the same density grade, it is found that the performance of AASFC with plant protein as foam stabilizer is the best.

Fair-faced concrete protective agent has excellent waterproof performance and excellent environmental protection performance. It can greatly prolong the service time of buildings being built with fair-faced concrete. For drawing the accurate conclusion that protective agents effects on carbonation resistance of fair-faced concrete, the test for the effect was done with permeable water-soluble silicone protective agent and acrylic film forming agent for protection. The test results show that both film forming agent for protection and permeable water-soluble silicone protective agent can effectively reduce the carbonation depth of fair-faced concrete, and the function of film forming agent for protection is better than that of permeable water-soluble silicone protective agent. Both the carbonation depths of test pieces coated with two different types of protective agents decrease along with the increase of curing age. Curing age and permeable protective agent can act separately while curing age and film forming agent for protection can boost each other, and the carbonation depth of fair-faced concrete can be further reduced because of the mutual action between the curing agent and the film forming agent for protection. A prediction model of the carbonation depth of fair-faced concrete was built. The influences of type and thickness of protective agents on carbonation resistance of fair-faced concrete were considered while being built.

To study the influence of different mass ratio of coarse particles (0.075~4.75 mm) to stone powder (<75 μm) of manufactured sand on the performance of rock powder concrete, rock powder (limestone powder and granite powder) was used to replace manufactured sand with different mass ratio to prepare high-strength concrete. The evolution laws of concrete fluidity, compressive strength, and durability (drying shrinkage and electric flux) under different sand-powder ratio were tested. The results show that when the sand-powder ratio of manufactured sand is not less than 9, the reduction of sand-powder ratio is conducive to improve the workability of concrete mixture and enhance the compressive strength and durability of concrete. Further reducing the sand-powder ratio has little effect on the drying shrinkage performance, but it is unfavorable to the fluidity, mechanical properties, and chloride ion permeability of concrete. Reducing the sand-powder ratio is conducive to improve the compactness of manufactured sand concrete. However, too low sand-powder ratio is easy to increase the water demand of concrete, and the content of free stone powder particles is too high, which will weaken the spatial structure of hydration products, and be unfavorable to the performance of concrete.

In order to explore the enhancement effect of basalt fiber on the punching shear resistance of concrete slab, and propose amendments to the calculation method for the punching shear bearing capacity of such components, based on the current norms in China. The volume content of fiber (0%, 0.1%, 0.2%, 0.3%) and the fiber length (12 mm, 18 mm) were taken as variables. The effect of each variables on the ultimate bearing capacity of seven concrete slab specimens was studied by punching shear test. Moreover, a finite element analysis model verified by the test was established for expansion parameter analysis. The results show that with the increase of volume content, the ultimate bearing capacity of basalt fiber concrete slab increases first and then decreases. Furthermore, the specimens of basalt fibers with a length of 12 mm and 18 mm are significantly higher than the specimens without fibers, with the maximum increase of 40.9% and 37.3%, respectively. The punching shear resistance of concrete slab is best improved when the fiber length is 12 mm and the volume content is 0.4%. The calculation value of the punching shear bearing capacity of the code for design of concrete structures (GB 50010—2010) in China is more conservative than the test results. Considering the effect of preventing cracking of basalt fibers on the circumference of critical section, the calculation formula of the punching shear bearing capacity of the code is modified.

To monitor the change of the internal defect degree and locate the defect position of the concrete structure in service, this paper explored a detection method based on stress waves and carries out experimental research. Piezoceramics transducer (PZT) was installed on the concrete surface in the form of an array, and the concrete was divided into different areas. One sensor in the array emitted waves and the other received waves, and sweep frequency mode and five peak pulse modes were used to monitor different areas of concrete. The test results show that when the stress waves pass through the area to be monitored, due to the existence of internal defects in the concrete, the amplitude value of the stress waves attenuates and the wave energy decreases. In order to quantify the degree of internal defects in concrete structures, the energy index and damage index based on the received signal are constructed and their functional relationships with the degree of defects are established, respectively. According to the difference between the energy index and damage index in different areas, the areas where internal defects exist in concrete are determined. The test results are consistent with the actual situation of the test pieces, which verifies the feasibility of using piezoelectric sensors to monitor the internal defects of concrete in this paper.

As a powder material, nano calcium carbonate after modsfication is usually used in various fields such as rubber, paper, paint and medicine. Various application fields have different requirement to the modification effect of nano calcium carbonate. Therefore, from the perspective of the modification effect of nano calcium carbonate, two influencing factors, namely the modification process and the modifier were analysed and introduced in this paper. The characteristics, advantages, disadvantages and modification mechanisms of these influencing factors were concluded. In addition, some common evaluation methods were introduced and the relevant influencing factors and testing methods were described. On this basis, this paper also provides an outlook on the development trend of nano calcium carbonate modification to help the practitioners in this field.

As the waste produced by coal mining and coal washing process, massive piling of coal gangue has a serious negative impact on the ecological environment, and using coal gangue as the aggregate of concrete is in line with the concept of green sustainable development. The loose and porous characteristics of coal gangue aggregate and the feature of showing needle-like or flaky after damage will negatively impact various coal gangue concrete properties. The basic physical and chemical properties of coal gangue aggregate were described briefly, while the effect of coal gangue aggregate on workability, mechanical properties, durability, and interfacial transition zone of concrete was also summarized. To compensate for the various defects of gangue aggregates used in concrete, reinforcement techniques relating to gangue aggregates have been proposed to improve the efficiency of gangue resource utilization. Four modification techniques-surface coating, such as water glass modification, thermal activation, and microbial-induced calcium carbonate precipitation techniques can strengthen coal gangue’s defects as an aggregate. On this basis, a summary of the strengthening mechanism and research progress of the above modification technology, and the future of the gangue aggregate and its modification technology in the concrete research direction were put forward to promote the application and development of coal gangue concrete.

In order to promote the application of coal gangue in concrete in cold regions, the coal gangue was compound activation by mechanical-microwave method. The damage and deterioration law of coal gangue powder concrete was studied from the aspects of apparent morphology, mass loss rate, relative dynamic elastic modulus, compressive strength and splitting tensile strength. The modification mechanism of activated coal gangue powder on the frost resistance of concrete was studied by scanning electron microscope, nuclear magnetic resonance spectrometer and X-ray diffractometer. The results show that activated coal gangue powder has the best effect on improving the frost resistance of concrete when it replaces cement with 20% (mass fraction). After 300 times freeze-thaw cycles, the mass loss rate and relative dynamic elastic modulus are 2.32% and 91.32%, and the compressive strength and splitting tensile strength decrease by 1640% and 26.12%, respectively. Activated coal gangue powder can fill and refine pores, and its secondary hydration can consume cement hydration product Ca(OH)2, and produce C-S-H and C-A-S-H, which can improve the compactness of cement paste, improve the pore structure and reduce the proportion of macropores.

The low-cost preparation approach of porous cordierite ceramics has always been a research hotspot for experts and scholars. In this study, taking asbestos tailings, fly ash and kaolin as raw materials, porous cordierite ceramics were successfully prepared by direct sintering method without adding foaming agent. The phase evolution, microstructure and physicochemical properties of porous cordierite ceramics were systematically studied. The results show that the increase of sintering temperature and the amount of kaolin contribute to the synthesis of cordierite, and the addition of kaolin can effectively reduce the foaming temperature and increase the porosity of samples. When the calcination temperature is 1 240 ℃ and the mass ratio of roasted asbestos tailings, roasted fly ash and kaolin is 5∶5∶3, the bulk density of porous cordierite ceramics is only 0.6 g/cm3, and the porosity reaches the maximum value of 76.94%. When the calcination temperature is 1 220 ℃ and the mass ratio of roasted asbestos tailings, roasted fly ash and kaolin is 5∶5∶5, the water absorption of porous cordierite ceramics reaches the maximum value of 34.57%. In addition, the porous cordierite ceramics show the good alkali resistance.

To enhance the erosion resistance of steam curing high-ferrite Portland cement (HFC) elements and promote the application of HFC in marine engineering, the effects of slag (SL) and fly ash (FA) on the capillary pore structure and erosion resistance of HFC based materials were investigated under steam curing conditions at 50 ℃ by means of mechanical properties tests, capillary pore tests, chloride binding tests and X-ray diffraction. The results show that the incorporation of SL improves the early mechanical properties of steam curing HFC mortar due to its higher pozzolanic reactivity, while reduces the 28 d capillary porosity of HFC mortar. The significant reduction of the early mechanical properties of HFC mortar is attributed to the incorporation of FA, inducing a slow strength gain in the later stage, whereas the capillary porosity of HFC mortar also decreases owing to the “micro aggregate” effect of FA. The chloride binding results indicate that SL and FA promote the physical adsorption and chemical binding of chloride by cement, respectively. Both SL and FA improve the chloride binding capacity of HFC composite cementitious materials.

KR desulfurization slag is a kind of waste residue produced by desulphurization process of hot iron. The synergistic preparation of cementitious materials with various solid wastes is an effective way to recycle the desulfurization slag. In this paper, KR desulfurization slag, granulated blast-furnace slag and desulfurization gypsum were used to prepare solid waste-based cementitious materials, and the effects of KR desulfurization slag content and granulated blast-furnace slag content on the mechanical properties of cementitious materials were studied, so as to optimize the ratio of raw materials. The hydration products and hydration characteristics of solid waste-based cementitious materials were studied by XRD, TG-DSC, IR, SEM-EDS and hydration heat test methods. The results show that the optimum ratio of solid waste-based cementitious materials is KR desulfurization slag 25% (mass fraction, the same below), granulated blast-furnace slag 60%, and desulfurized gypsum 15%. The 3 d, 28 d and 90 d compressive strength of cementitious materials reach 30.01 MPa, 49.47 MPa and 55.73 MPa, respectively. The early hydration heat release rate of solid waste-based cementitious materials is low, and the cumulative heat release in 3 d is only 37.9% of ordinary Portland cement (OPC). The main hydration products are needle-rod ettringite (AFt) and amorphous calcium silicate hydrate (C-S-H) gel. A large amount of Ca(OH)2 in KR desulphurized slag can excite the slag alkali at the early stage of hydration to disintegrate the glassy silicate, and react with desulphurized gypsum to promote the formation of AFt. In the later stage of hydration, the synergistic reaction of KR desulfurization slag, granulated blast-furnace slag and desulfurized gypsum makes the hydration products increase continuously, and the dense structure is formed by mutual cementation, which is conducive to the continuous growth of strength.

In order to improve the comprehensive utilization of industrial solid waste such as iron tailings and desulfurization ash, sodium hydroxide and calcium sulfate were used as composite excitant, and iron tailings powder, desulfurization ash and slag powder were used as raw materials to prepare iron tailings powder-desulfurization ash cementitious material. The orthogonal test was carried out to analyze the effects of iron tailings powder content, desulfurization ash content, sodium hydroxide content and calcium sulfate content on the compressive strength of the cementitious material and the mix proportion was optimized. The microstructure was characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The results show that the content of sodium hydroxide, iron tailings powder and calcium sulfate has the most significant effects on the 3 d, 7 d, and 28 d compressive strength of the cementitious material, respectively. The optimal content of iron tailings powder, desulfurization ash, sodium hydroxide and calcium sulfate are 20%, 10%, 1% and 9% (mass fraction), respectively. Meanwhile, the 3 d compressive strength of cementitious material is 4.59 MPa, and the 28 d compressive strength is 18.44 MPa, with a dense microstructure and the highest macroscopic strength.

By alkali activation reaction, compression moulding and carbonated conservation, copper tailings cured bricks were prepared using fine-grained copper tailings as main raw material, sodium silicate as activator, with a small amount of cement and fly ash. The phase composition, carbonized products, pore distribution and microscopic morphology of different samples were analyzed by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), mercury intrusion porosimeter (MIP) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS). Then, the synergistic mechanisms of alkali activation-carbonated conservation on the performance improvement of copper tailings cured bricks were discussed. The results show that sodium silicate can stimulate part of the gelling activity of copper tailings, and generate flocculated calcium silicate hydrate (C-S-H) gels to improve the microscopic pore structure and the compressive strength of the cured bricks. Timing of carbonated conservation is critical. If the cured brick is carbonated conservation immediately after forming, the carbonization reaction will compete with the alkali activation reaction for OH- to generate aragonite-type and calcite-type CaCO3, resulting in the reduction of C-S-H gel generation, and then causing increasing porosity, and compressive strength reduction. When the cured brick is cured for 84 h in airtight condition and then carbonated cured for 84 h, the 7 d compressive strength would increase by 20.9%, and the internal pores are filled with the carbonized product CaCO3, in which the volume of harmful pores and multi-harm pores greatly reduce and the number of harmless pores increases, thus improving the overall structure density, there by solving the problem of efflorescence on the surface of the copper tailings cured brick.

The steel slag-miscellaneous fill base was prepared by mixing steel slag, slag micropowder and waste concrete debris, and its performance was studied. The volume stability test shows that the slag micropowder has obvious anti-expansion effect. The 10 d high temperature water bath expansion rate of the specimen mixed with 50% (mass fraction, the same below) steel slag, 50% miscellaneous fill and 30% slag micropowder is only 1.32%, while the 3~5 d expansion rate of the specimen without slag micropowder exceeds the 2% limit. The orthogonal test of 7 d unconfined compressive strength and 28 d splitting strength shows that the order of influencing factors of 7 d unconfined compressive strength and 28 d splitting strength is steel slag, cement content, concrete debris proportion and soil stabilizer. The maximum values of 7 d unconfined compressive strength and 28 d splitting strength in each group are 12.41 MPa and 2.24 MPa, respectively. The optimum ratio of steel slag-miscellaneous fill base is 50% steel slag, 50% miscellaneous fill (m(concrete debris)∶m(plain soil)=6∶4), adding 40% slag powder, 5% cement and 0.018% stabilizer. At this time, the specimen has good water stability. The test of strength influencing factors show that slag micropowder has the greatest influence on the increase of specimen strength. X-ray diffraction and scanning electron microscope analysis show that f-CaO in steel slag is effectively digested under the action of slag micropowder and soil stabilizer. The dense package of aggregates, concrete particles and steel slag particles prevents the volatilization of internal water and the invasion of external free water, which not only ensures the strength of steel slag-miscellaneous fill base, but also effectively inhibits the expansion.

By means of rotational rheometer, microcalorimeter, environmental scanning electron microscope (ESEM) and X-ray diffractometer (XRD), the effects and mechanism of three kinds of water reducer including naphthalene formaldehyde sulfonates (NFS), sulfonated melamine formaldehyde (SMF) and polycarboxylate (PC) on the rheological and setting properties of high-strength gypsum paste (HSGP) were studied systematically. The results show that the order of improving the fluidity of HSGP by the three water reducers is PC>SMF>NFS. The deflocculation effect of water reducer promotes the dissolution of hemihydrate gypsum, delays the nucleation of dihydrate gypsum, and causes the HSGP to produce segregation and shear-thickening. Under the saturated content, NFS delays the nucleation of dihydrate gypsum, but promotes the growth and formation of crystal-network-structure (CNS) of dihydrate gypsum, so it has little effect on the early hydration and setting time of HSGP. SMF promotes both the growth and formation of CNS of dihydrate gypsum crystals, without affecting the nucleation of dihydrate gypsum, thus accelerating the early hydration process of HSGP and shortening the setting time significantly. PC hinders both the nucleation and growth of dihydrate gypsum crystals, thus greatly postponing the early hydration process of HSGP and linearly improving the setting time.

The effects of different length and content of ramie fibers on the water resistance and mechanical properties of ramie fiber reinforced calcined phosphogypsum composite materials were studied through the tests of water absorption, softening coefficient, flexural strength and compressive strength, combined with Fourier transform infrared spectroscopy and scanning electron microscopy. The results show that adding ramie fiber can improve the water resistance and mechanical properties of ramie fiber reinforced calcined phosphogypsum composite materials, and also promote the ductility of composite materials. Adding 0.5% (volume fraction, the same below) 10 mm ramie fiber makes the softening coefficient of composite materials reach the maximum, which increases by 20.0% compared with the control sample. The incorporation of ramie fiber can effectively improve the flexural strength of composite materials. At the age of 28 d, the flexural strength of composite materials with 1.5% 10 mm ramie fiber increases by 39.5% compared with the control sample. The compressive strength of composite materials with less than 20 mm ramie fiber decreases, but increases by addition of less than 1.5% 30 mm ramie fiber. At the age of 28 d, the compressive strength of composite materials with 1.5% 30 mm ramie fiber increases by 10.1% compared with the control sample. Ramie fiber hydrolyzes in the composite materials matrix. The degree of hydrolysis increases and the surface becomes rougher with the increase of age.

Foam insulation material was prepared by recycled powder (RP) using wet foam mixing method. The effect of slurry composition on foam survival state was discussed by measuring foam stability time, slurry setting process, compressive strength, dry density, porosity and thermal conductivity. The maximum content of RP was also investigated. The results show that there is a suitable matching state between the stability of foam and the viscosity and setting process of slurry. The preformed foam has a good survival state when the water to solid ratio is 0.80, the viscosity of slurry is about 1.7 Pa·s, and the final setting time of slurry is less than 30 min. The maximum content of RP can reach 70%. The compressive strength of prepared foam insulation material is 1.15 MPa, and the thermal conductivity is 0.118 W/(m·K), which meet the requirements of JG/T 266—2011 foam concrete standard A06 grade.

To solve the problem of massive piling and overcome the difficulty of treatment for waste wind turbine blade (WTB), the recycled WTB (rWTB) fiber was obtained by mechanical crushing, and the influence of rWTB fiber content (0%, 10%, 20% and 30%, mass fraction) on the mechanical properties and frost resistance of concrete were investigated. The economic and environmental benefits of the reuse of waste WTB in concrete were discussed. It is revealed that adding 10%, 20% and 30% rWTB fiber significantly increase the flexural strength and splitting tensile strength of concrete, the flexural strength of concrete increases by 2.8%, 2.8% and 11.1%, and the splitting tensile strength increases by 56.3%, 68.8% and 40.6%, respectively. The freeze-thaw cycles of 20% rWTB fiber concrete are 75 times, far exceeding that of plain concrete (25 times), illustrating the highly improved frost resistance. However, the compressive strength and frost resistance decrease with excessive addition of rWTB fiber (30%), and the water absorption increases obviously. Compared with the incineration treatment, adding 20% rWTB fiber can reduce the cost of concrete by 69.2 yuan/m3 and the CO2 emission by 0.04 t/m3.

In order to explore the toughening effect of recycled rubber aggregate in geopolymer concrete, different proportion of recycled rubber aggregate (particle size 0.15~0.3 mm and 1~4 mm) was used to replace the natural aggregate in geopolymer concrete. Firstly, geopolymer cementitious material was prepared with granulated blast furnace slag powder as raw material, sodium silicate solution and NaOH as activators, and combined with natural aggregate and recycled rubber aggregate to prepare geopolymer rubber concrete. Then the mechanical properties, impact resistance and strength mechanism of geopolymer rubber concrete were studied. The results show that the compressive strength of geopolymer concrete can be improved with an increase of about 5% by adding an appropriate proportion of recycled rubber aggregate, which is related to the oxidation and degradation of recycled rubber aggregate surface in NaOH alkali environment. However, geopolymer rubber concrete is easy to fracture under indirect tensile load and bending load, and the indirect tensile strength and flexural strength are reduced by 20%~30%, which is a typical feature of geopolymer rubber concrete. In drop hammer impact test and flexural tensile impact test, recycled rubber aggregate can greatly improve the impact resistance of geopolymer concrete with the maximum increase up to more than 200%. It is due to the flexible and elastic characteristic of recycled rubber aggregate, which absorbs some impact energy. At the same time, recycled rubber aggregate also delays the process from initial cracking to failure of concrete under impact load, reduces the stress concentration of crack cracking, and improves the ductility of geopolymer concrete. Under the alkaline condition of geopolymer, the surface of rubber particles is oxidized and degraded, and the surface becomes rough and closely combines with geopolymer matrix. Under the action of NaOH, hydrophilic groups such as hydroxyl and carboxyl groups are produced on the rubber surface, which is conducive to the adhesion of hydration products on the surface of recycled rubber aggregate.

Pore structure is an important composition of concrete microstructure and affects the macroscopic properties of concrete. This paper aims to study the effect of the substitution of municipal solid waste incineration bottom ash (MSWIBA) for natural sand on the pore structure and compressive strength of concrete. Nuclear magnetic resonance technology was employed to investigate the porosity and the variation character of the pore size distribution for concrete with MSWIBA. Meanwhile, according to the fractal theory, the fractal characteristics of pores were explored, and the fractal dimension of each pore size interval and the overall fractal dimension were obtained. Moreover, the grey entropy correlation degree between each pore size ratio, porosity, fractal dimension, and compressive strength was discussed. The results show that the porosity of concrete increases, and the proportion of harmless pores and compressive strength decrease with the increase of the replacement of natural sand with MSWIBA. Furthermore, the fractal dimension decreases with the increase of the content of MSWIBA. The fractal dimension increases and the pore structure is improved with age due to the potential hydraulic properties of MSWIBA. Meanwhile, the overall fractal dimension and the proportion of harmless pores of concrete with MSWIBA have the greatest influence on the compressive strength based on the grey entropy correlation degree analysis.

Lanthanum chromate ceramics have been widely used in many fields because of their excellent properties. Dense lanthanum chromate ceramics can be used as the solid oxide fuel cell connector materials for high temperature. This paper reviewed the synthesis method of lanthanum chromate powder such as the solid phase method, sol-gel method, combustion and hydrothermal method, and also analyzed the reasons for difficult densification of lanthanum chromater ceramics. Based on current preparation methods, a variety of new sintering methods for densification of lanthanum chromate ceramics were investigated. At the same time, the progress of the improvement of electrical properties was investigated by doping modification at different positions, compositing and other methods. At last, the future research and development directions were prospected.

Bioglass ceramic bone implants prepared by photocuring technology have many advantages in the field of bone repair. However, due to the influence of powder particle size, there are great differences in photocuring printing process, structure, mechanical and biological properties of bioglass ceramics. In this paper, based on the change of particle size in the process of photocuring 3D printing, two kinds of bioglass ceramic suspension with different particle sizes were prepared. The stability, rheological properties and curing behavior of bioglass ceramic suspension were characterized, respectively. Besides, the debinding sintering curve was drawn according to TG-DSC curves, and the surface quality, structure and mechanical properties of bone scaffold were evaluated. At last, the degradation performance was analyzed by skull repair experiment. The results show that the suspension with small particle size powder has good stability and high viscosity, and its corresponding curing depth and over-curing width are also small. The surface quality, structural densification and bending strength of bone scaffold prepared with small particle size powder are better than those prepared with large particle size powder. However, the degradation rate of bone scaffold prepared by small particle size powder is slow. After 2 months of implantation, new bone tissue in the scaffold pores is observed. This study provides guidance for the preparation of bioglass ceramic bone scaffolds with different particle sizes, which will help to promote the development and application of gradient controllable degradable bone scaffold based on particle size distribution.

The structural instability of yttrium hexaboride (YB6) at high temperature limits its application in the ultra-high temperature field. By introducing Yb element, high-temperature stable (Y1-xYbx)B6 solid solution can be formed. In this paper, (Y0.5Yb0.5)B6 powders were prepared via boron/carbon thermal reduction method using (Y0.5Yb0.5)2O3 and B4C as raw materials, and the ceramics were densified by pressureless sintering. The crystal structure, microstructure and mechanical properties were investigated based on the experimental results and density functional theory calculations. The results show that the (Y0.5Yb0.5)B6 powders synthesized at 1 650 ℃ have the highest purity when B4C is excess by 6.25%. (Y0.5Yb0.5)B6 ceramics have a relative density of 95.80% after pressureless sintered at 2 000 ℃, but the grains are coarse with the average size of (80.71±35.51) μm. The relative density, grain size, hardness and fracture toughness of ceramics obtained by two-step sintering are 95.47%, (14.54±6.31) μm, (14.53±1.37) GPa and (2.81±0.34) MPa·m1/2, respectively. The fracture morphology of ceramics is very similar to that of typical high damage tolerance ceramics Ti3SiC2 and Hf3AlN, which indicates that (Y0.5Yb0.5)B6 has good damage tolerance and is expected to improve the toughness and ductility of ultra-high temperature ceramics.

To toughen Si3N4-based ceramic materials, W/Si3N4 composite ceramic materials were prepared in this article by the pneumatic sintering method with tungsten (W) as the second phase material and Y2O3-Al2O3 as sintering additive. Then the effect of W content on the compactness, mechanical properties, and microstructure of W/Si3N4 composite ceramic materials was investigated. The results indicate that the densities of samples all reach more than 97% when the W content is less than 5% (mass fraction). The most outstanding overall performance of W/Si3N4 composite ceramic materials is obtained when W content is 5% (mass fraction), and the bending strength, hardness, and fracture toughness are (670.28±40.00) MPa, (16.42±0.22) GPa, and (8.04±0.16) MPa·m1/2, respectively, which are 3808%, 13.08%, and 44.34% higher than Si3N4 ceramic materials without the addition of metal W. By analyzing the microstructure of the polished surface and indentation cracks of W/Si3N4 composite ceramic material samples, it is found that the introduction of W can trigger toughening mechanisms such as deflection and bifurcation of cracks in the propagation path, and consume crack expansion energy, thus improving the fracture toughness of Si3N4 ceramics.

Using KMnO4 and MnSO4·H2O as raw materials, active manganese dioxide was prepared at room temperature and pressure and hydrothermal condition. The synthesized active manganese dioxide was characterized by XRD, TEM and N2 adsorption-desorption, respectively. The effects of different preparation methods on structure and adsorption performance of the synthesized products were investigated. The results show that the reaction temperature and pressure have a great effect on the morphology and adsorption performance of active manganese dioxide. The shapes of active manganese dioxide prepared at room temperature and pressure are all rod. The products synthesized by hydrothermal method are mesoporous fibers and have better adsorption performance. The adsorption behavior of 2,4-dinitrophenol on active manganese dioxide is well described by Langmuir isotherm equation (R2>0.99) and pseudo-second-order kinetic equation (R2>0.99), which indicate that the adsorption process is monolayer and chemical adsorption. The pH value of solution has a significant effect on the adsorption of 2,4-dinitrophenol on active manganese dioxide, and the maximum adsoption capacity is 2.539 mg/g at pH=7.

The crystal quality is the key to determining the absorption efficiency of the copper-zinc-tin-sulfur-selenium (Cu2ZnSn(S,Se)4, CZTSSe) absorber layer thin film, and spin coating is the first step in the preparation of the CZTSSe absorber layer by solution method, therefore, the choice of the spin coating method is crucial. To explore the effects of different spin coating modes on the quality of CZTSSe absorber layer thin film and the performance of corresponding devices, three groups of copper-zinc-tin-sulfur (Cu2ZnSnS4, CZTS) precursor thin films were prepared by different spin coating modes and the effects of different spin coating modes on the crystal structure, element composition, phase purity and surface morphology of CZTSSe absorber layer thin films were analyzed by X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), Renishaw Raman system (Raman), and field emission scanning electron microscope (FE-SEM), separately. At the same time, the photoelectric characteristics of the CZTSSe thin film solar cell were characterized by current density-voltage (J-V) characteristic and external quantum efficiency (EQE) tests. The results show that the spin coating mode with 7 cycles and 2 times spin coatings before each baking in the first cycle result in uniform CZTS precursor thin films without cracks, higher crystallinity of CZTSSe absorber layer thin films, flatter, and denser film surface, and more uniform grain size. As a result, the CZTSSe thin film solar cell with a photoelectric conversion efficiency of 9.63% is realized. Through the statistical analysis of the performance parameters of devices based on different spin coating modes, it concludes that the new spin coating modes can improve the repeatability of CZTSSe thin film solar cells and pave the way for possible large-scale commercial applications in the future.

In this paper, g-C3N4 and In2S3 were synthesized by thermal polycondensation and hydrothermal method, respectively. In2S3/g-C3N4 composite photocatalyst was prepared by simple mechanical grinding technology. The crystallographic structure, morphology, microstructure and optical properties of In2S3/g-C3N4 composite photocatalyst were characterized by X-ray diffraction (XRD), scanning electron microscope(SEM), transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), and UV visible diffuse reflectance spectrum (UV-Vis DRS). The photocatalytic activity was evaluated by degradation of tetracycline (TC) under visible light irradiation. The results show that the In2S3/g-C3N4 composite photocatalyst with grinding molar ratio of 1∶4 displays the best photocatalytic activity. The observed rate constant of TC degradation under xenon lamp is 0.025 1 min-1, which is 2.9 times and 1.6 times higher than that of In2S3 and g-C3N4, respectively. The observed rate constant of TC degradation under natural light is 0.010 4 min-1, which is 2.6 times and 1.4 times higher than that of In2S3 and g-C3N4, respectively. The superior photocatalytic performance of In2S3/g-C3N4 composite photocatalyst is attributed to the efficient migration and separation of charge carriers and the enhanced light absorption capacity. This paper provides a promising approach for designing and developing visible-light-response photocatalysts applied to antibiotic wastewater treatment.

To prepare thermal insulation refractory for high-temperature kilns with excellent thermal insulation and mechanical properties, porous spherical mullite-based castable was prepared with porous spherical mullite, bauxite powder, α-Al2O3 powder, silica powder, and Secar71 cement as main raw materials. The effect of bauxite powder content on mechanical properties, thermal conductivity, corrosion resistance, and thermal shock stability of porous spherical mullite-based castable was studied. The results show that changing the content of bauxite powder can improve the thermal insulation, thermal shock stability, and corrosion resistance of porous spherical mullite-based castable while maintaining high mechanical properties. As the content of bauxite powder increases, the mechanical properties of porous spherical mullite-based castable change little, but the thermal conductivity decreases slightly, the corrosion resistance is quite different, and the thermal shock stability increases first and then decreases. When the bauxite powder content is 28%(mass fraction), the mechanical properties, thermal shock stability, and corrosion resistance of porous spherical mullite-based castable are excellent, and the thermal conductivity at 1 000 ℃ is 0.905 W·m-1·K-1. The thermal conductivity of porous spherical mullite-based castable is lower than that of high-alumina castable for tundish and ladle permanent layer, therefore, it can be used as a substitute for high-alumina castable for tundish and ladle permanent layer, and its heat loss can be reduced.

The molten iron ladle lining material has long service in alternating environments with long intervals of high and low temperatures, which is very prone to peeling and corrosion damage. To explore the main factors affecting the service life of the molten iron ladle lining material, the chemical composition, phase composition, physical properties and microstructure of the four molten iron ladle Al2O3-SiC-C lining bricks on the market were analyzed. The corrosion mechanism of molten iron ladle Al2O3-SiC-C lining brick for stainless steel smelting was mainly studied by using blast furnace slag as a corrosion medium. The results show that the higher the content of Al2O3 in the molten iron ladle Al2O3-SiC-C lining brick, the lower the liquid phase content of the product at high temperature, which is more conducive to improving the high temperature mechanical properties of the refractory brick. With the increase of carbon content, the slag resistance of molten iron ladle Al2O3-SiC-C lining brick is improved, but the oxidation resistance and high temperature flexural strength show a downward trend. CaO and MgO in the furnace slag penetrate the refractory brick and react with Al2O3 and SiO2 in the refractory brick to form magnesium-aluminum spinel with high melting point and calcium feldspar with low melting point, etc., and the low melting phase will aggravate the corrosion of refractory bricks.

The argon oxygen decarburization (AOD) furnace smelting process is widely used in the stainless-steel production. The corrosion mechanism of AOD slag to MgO-C bricks used by ladle lining was studied to provide theoretical basis for improving the service life and performance of MgO-C bricks used by ladle lining. The phase change, microstructure and chemical composition change of MgO-C bricks after corrosion were analyzed by FactSage6.2 software, X-ray diffraction (XRD), field emission scanning electron microscope (SEM) and energy dispersion spectrum (EDS). The results show that, as the corrosion reaction proceeds, periclase is gradually eroded, and the low melting point phases such as Ca3MgSi2O8 and the high melting point phases such as MgAl2O4 gradually appear. The corrosion is resulted by the penetration of AOD slag through the matrix in the MgO-C bricks, and the reaction between slag and periclase to form Ca3MgSi2O8. The generation of MgAl2O4 at the boundary of periclase hinders the corrosion of AOD slag to MgO-C bricks.

In this paper, corrosion resistance experiment on fused-cast refractory materials was performed to study the cast refractory materials. The erosion behaviors of soda-lime glass, high aluminum glass and lithium aluminum glass on fused-cast refractory materials were studied by chemical analysis, lithofacies analysis and electron microscopy spectroscopy analysis. The results show that the alkali metal ions in the molten glass diffuse to the glass phase of the refractory, which leads to the viscosity of the glass phase decrease. At the same time, the corundum phase dissolves and the inclined zircon disperses, then the main structure of the refractory is destroyed, and the interfacial layer is formed. There is a glass phase rich in aluminum and zirconium in the interface layer. Due to the high alumina content and high surface tension of high aluminum glass and lithium aluminum glass, the glass phase in the interface layer gathers around the sample and diffuses slowly, thus preventing the development of erosion. The erosion rate of the molten glass is: soda-lime glass>high aluminum glass>lithium aluminum glass.

Due to the influences of rock types and mechanical properties, the obvious differences of morphological characteristics are existed in the aggregate produced by conventional technologies. It is difficult to qualitatively-quantitatively study the influences of aggregate morphological characteristics on the performance of asphalt mixture. Therefore, a preparation method of artificial aggregates with adjustable morphological characteristics, mesh size and volume was proposed based on 3D printing technology in this study. First, three-dimensional models of aggregates with different morphological characteristics were obtained by scanner, and the mesh size and volume of the models were adjusted by the software. The polylatic acid (PLA) was used as raw material to 3D print aggregate particles with specific morphology, mesh size and volume. Then, cement mortar was selected as raw material and silicone replication method was used to prepare artificial aggregates with specific morphological characteristics. The results show that the surface area error of the prepared artificial aggregates is less than 6% and the volume error is less than 3%. The performance indicators of crushing value, wear loss value, firmness and adhesion grade meet the specification requirements. Based on 3D printing technology, the artificial aggregates with good morphological characteristics, specific mesh size and volume can be made to replace natural aggregates. It provides technical support for further research on the influences of aggregate morphological characteristics on asphalt mixture performance.

Developing new green road building materials with high early strength and low energy consumption is of great significance to highway construction and maintenance in China. The geopolymer stabilized cold recycled mixture (GCRM) was prepared by using geopolymer to stabilize 100% recycled asphalt mixture in this paper. The effects of slag content, water glass modulus, activator content and geopolymer content on the splitting strength of GCRM with different curing time and its time-varying law were studied. The microscopic morphology and structural composition of the mixture were analyzed by scanning electron microscopy and energy dispersive spectroscopy. The results show that the early strength of GCRM develops rapidly, which is significantly higher than that of cement emulsified asphalt stabilized cold recycled mixture. GCRM has the best early strength and its 7 d splitting strength can reach 1.7 MPa when the slag content is 30% (mass fraction), the water glass modulus is 1.0, the activator content is 50%(mass fraction) and the geopolymer content is 8% (mass fraction). Microstructure analysis shows that the cracks of GCRM failure interface appear in the position with low geopolymer reaction degree. Besides, the calcium aluminosilicate hydrate (C-A-S-H) layered gel structure is more conducive to the development of the mechanical strength for GCRM.

In order to solve the disease problem of Suida expressway, the loess-like sub-sandy soil was modified by the addition of new materials lithium silicate, lime and polypropylene fiber. The strength characteristic, microscopic mechanism, curing mechanism and pore structure of the modified soil were studied by the freeze-thaw cycle test, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the addition of lithium silicate can greatly improve the unconfined compressive strength of lime modified soil. The optimal mix ratio of composite modified soil is that: the content of lithium silicate is 3% (mass fraction), the content of lime is 6% (mass fraction), the content of polypropylene fiber is 0.4% (mass fraction) and the fiber length is 12 mm. The destructive form of composite modified soil is "ductile failure", and the polypropylene fiber plays a pulling role in its stress process, so that the specimen can withstand greater stress within a certain strain range. Regardless of whether the modified soil is in a standard conservation environment or a freeze-thaw cycle environment, lithium silicate can play the role of soil strength enhancer, provide an alkaline environment, intensify the hydration reaction, and generate new substances such as albite, C-A-S-H gel, Li［AlSi4O10］and so on. The formation of hydration products is the main reason for the decline of soil porosity related parameters. The standard conservation environment and alkaline environment can promote the hydration reaction, improve the decline of pore parameters, and effectively improve the strength of modified soil.