Low-heat Portland cement is widely accepted in high-grade mass concrete projects for its low hydration heat to reduce the risk of structural cracking caused by thermal stresses. In addition, the stability of strength growth under high temperature determines that it can be used in high temperature engineering environment. Competent volume stability is beneficial to solving the problem of concrete structure cracking. High late-strength and corrosion resistance are suitable for the production and application of high-performance concrete. In this paper, some keypoints of low-heat Portland cement in hydration control, hydration products, microstructure and performance optimization were analyzed from the aspects of hydration process and performance characteristics. The performance characteristics of low-heat Portland cement such as hydrating stably in high temperature environment, corrosion resistance and volume stability were summarized, and the new application prospect of low-heat Portland cement in extreme environment and high heat environment was put forward.

The rapid setting characteristic of potassium magnesium phosphate cement (MKPC) limits its application and development in engineering fields. Effectively prolonging the setting time is one of the key technologies for its engineering application. In this study, the effect of borax/triethanolamine composited retarder on the setting time, compressive strength, phase composition, micromorphology, pore structure and hydration heat release properties of MKPC was studied, and the retarding mechanism was discussed. The results show that the setting time of 26~100 min can be controlled by using the composited retarder under the condition that the 7 d compressive strength is greater than 20 MPa. Triethanolamine molecule is adsorbed on the surface of MgO and plays a role in water blocking, which significantly reduces the standard hydration heat release rate and standard hydration heat release, and achieves the retarding effect. The decrease of K-struvite content and the increase of pore (larger than 10 nm) volume are the main reasons for the weakening of compressive strength.

Limestone and metakaolin partially replace cement can effectively reduce the carbon emissions of cement products. The rheological properties of fresh limestone-metakaolin-cement paste system were tested by Antonpa MCR 302 rotary rheometer. Simplex barycenter method was applied to limestone-metakaolin-cement mortar system. The rheological properties of mortar with different ratios were tested by Viscometer 5 concrete rheometer. The results show that the yield stress and the plastic viscosity of cement paste increase significantly with the increase of metakaolin content. However, with the increase of limestone, the yield stress and the plastic viscosity of cement paste increase first and then decrease. Changing the ratio of binders significantly affects the fluidity and the rheological parameters of mortar.

In order to study the influences of limestone powder parameters on the hydration heat of cement, the effects of different content and particle size of limestone powder on the hydration heat and hydration heat rate of cement were analyzed by TAM Air-eight-channel microcalorimeter. The results show that with the increase of content of limestone powder, the hydration heat and hydration heat rate of auxiliary cementitious materials generally show a trend of decreasing. The hydration heat and hydration peak rate of 15% (mass fraction) limestone decrease the most, the hydration heat at 400 mesh is 223.22 J/g, the hydration peak rate is 2.399 2 mW/g, the hydration heat at 3 000 mesh is 215.98 J/g, and the hydration peak rate is 2.214 0 mW/g. Meanwhile, when the content of limestone powder is large, the influence of particle size on the hydration reaction is more obvious. Too small or too large particle size will increase the hydration heat and hydration heat rate. When the particle size of limestone powder is 1 250 mesh, the hydration heat is small and the hydration heat rate is low. Through phase analysis, it is found that the system with limestone powder do not produce new substances. When the content of limestone powder is 15% (mass fraction) and the particle size is 1 250 mesh, the diffraction peak intensity of Ca(OH)2 is the highest and accompanied by the formation of a large amount of C-S-H, indicating that this group of limestone powder can greatly promote the hydration reaction of cement.

The cement materials were prepared by self-prepared poly N-isopropylacrylamide (PNIPAM) thermosensitive gel, and the sulfate solution attack test was carried out to measure the mass and strength changes of specimens. In addition, SEM, MIP and hydration heat test were used to study the effect mechanism of PNIPAM gel on the sulfate attack resistance of cement materials. The results show that PNIPAM gel phase transition can release water, promote the hydration of cement materials, improve the internal pore structure, and enhance the mechanical properties of cement materials. 1.0% (mass fraction) PNIPAM gel can reduce the mass loss and strength loss of cement materials subjected to sulfate attack. The PNIPAM gel can counteract the internal damage caused by some expansive erosion products and improve the sulfate attack resistance of cement materials due to its phase transformation characteristics.

In order to improve the impermeability and crack resistance ability of cement mortar, a new type of cement mortar material was developed in this paper. Through the preparation of bentonite and basalt fiber modified cement mortar with different content, the impermeability and crack resistance were tested, and the micro mechanism of cement mortar was analyzed. The results show that the addition of bentonite and basalt fiber enhances the impermeability and crack resistance of cement mortar. When 4% (mass fraction) bentonite and 0.4% (mass fraction) basalt fiber are mixed, the impermeability pressure of cement mortar is the highest, which increases by 61.11% compared with the group without bentonite and basalt fiber, and the impermeability grade is P8. At the same time, the crack reduction factor of cement mortar mixed with bentonite and basalt fiber reaches more than 80%, the crack resistance grade belongs to grade I, and the characteristics of cracks are "few, fine and short". Mixing bentonite and basalt fiber improves the compactness of cement mortar and reduces cracks and holes. The addition of bentonite and basalt fiber does not change the type of hydration products of cement mortar, but reduces the crystallinity of calcium hydroxide and promotes the formation of calcium silicate hydrate gel.

The aggregate selected for concrete in Xinjiang Dashixia water control project has alkaline activity, which may lead to the problem of alkali aggregate damage in project. The effects of local fly ash (FA) and ground granulated blast furnace slag (GGBFS) on alkali-silica reaction (ASR) were investigated. In addition, XRD and SEM-EDS were used to analyze hydration products and morphology of interface transition zone (ITZ). FA content ≥20% (mass fraction) or GGBFS content ≥40% (mass fraction) can significantly inhibit alkali-silica reaction. Amorphous phase is observed in interfacial transition zone of pure cement samples, and no amorphous phase is observed in samples containing FA or GGBFS, which means that the alkali-silica reaction occurs in pure cement samples. The addition of FA or GGBFS reduces the Ca/Si molar ratio of interfacial transition zone phase and inhibits alkali-silica reaction.

In order to explore the effect of fiber volume content on the fracture process of polyvinyl alcohol fiber reinforced engineering cementitious composites (PVA-ECC), the split Hopkinson pressure bar (SHPB) device based on 50 mm was used for different fiber volume content (0%, 0.75%, 1.50%, 2.25%, 3.00%) of PVA-ECC notched semi-circular bend (NSCB) specimens for impact test, and combined with ultra-high-speed digital image correlate (DIC) test system for PVA-ECC materials. The dynamic fracture process was experimentally studied, and the variation law of the prefabricated crack tip opening displacement and the critical crack tip opening displacement (CTODC) value of each group of specimens were obtained. The results show that when no PVA fiber is added or a small amount (less than 1.50%) is added, the macroscopic crack at the crack tip appears basically at the peak moment of the crack tip load, and with the increase of the PVA fiber content, the macroscopic crack at the crack tip appears. It appears significantly earlier than the peak time of the crack tip load, and the larger the fiber volume content is, the earlier the crack tip macro crack appears, and the time for the crack to expand to complete fracture also increases significantly. The addition of polyvinyl alcohol fibers significantly improves the performance of concrete specimens. The increase of CTODC value can improve the crack resistance of the specimen. Under the same impact load, the specimen added with 2.25% polyvinyl alcohol fiber has a larger CTODC value.

The damage caused by alternating wetting and drying and sulfate corrosion seriously affects the long-term stability of conductive concrete in service. In this study, carbon fiber and graphite were used as conductive phase materials, and fly ash and silica fume were mixed to prepare conductive concrete. The effects of fly ash and silica fume content on mechanical and electrical properties of conductive concrete under alternating wetting and drying and sulfate corrosion were discussed. The degradation index of service performance was defined by integrating the decay of mechanical and electrical properties of conductive concrete. The results show that the addition of fly ash and silica fume can effectively improve the durability and conductivity stability of conductive concrete under alternating wetting and drying and sulfate corrosion. When the total content of fly ash and silica fume is fixed, the high content of fly ash can effectively reduce the strength loss caused by alternating wetting and drying and sulfate corrosion, and improve the conductive stability of conductive concrete.

In order to improve the homogeneity of lightweight concrete and enhance the mechanical properties of lightweight concrete, the Herschel-Bulkley (H-B) plastic viscosity calculation model was established to explore the influences of rheological characteristics of foamed slurry on the foam settlement and ceramsite distribution in slurry. The results show that with the increase of thickener content, the yield stress and the plastic viscosity of lightweight concrete foamed slurry based on nonlinear H-B model ηH-B=0.016 67K(80n-20n) (ηH-B is the plastic viscosity of foamed slurry obtained by H-B calculation model; K is consistency coefficient; n is flow index) increase. As a result, the settlement distance of foamed slurry decreases and the fractal dimension of ceramsite in slurry increases. When the plastic viscosity of foamed slurry is greater than 1.74 Pa·s and the yield stress is greater than 92.87 Pa, the lightweight concrete with compressive strength greater than 10 MPa is prepared. It is seen that optimizing the rheological properties of the foamed slurry is the key to overcome the easy floating problem of ceramsite in foamed slurry, which can effectively improve the homogeneity of lightweight concrete and enhance the mechanical properties of lightweight concrete.

In order to adapt to the current trend of building industrialization and solid waste recycling, a new technology of vacuum water-removal and compression was proposed in the engineering field to achieve a highly efficient pre-fabrication of machine-made sand concrete. In this study, the effect of the time of vacuum water-removal and compression treatment on the performances of machine-made sand concrete with varied initial water-to-cement ratio (W/C) was investigated. Results show that vacuum water-removal and compression can significantly improve the strength of machine-made sand concrete as compared to natural sand concrete, primarily due to the locking effect of the machine-made sand under the condition of high compaction by the treatment. The initial W/C of machine-made sand concrete decreases from 0.58 to 0.32 and the compressive strength increases by 44.6% after being treated with -0.07 MPa vacuum pressure and 15 MPa compression for 100 s. However, the improvement of performances weakens with prolonged treatment time, especially for concrete with lower W/C. Mercury intrusion porosimetry (MIP) results reveal that the porosity of concrete decreases significantly after vacuum water-removal and compression treatment. In particular, the proportion of capillary pores with pore size larger than 50 nm decreases by more than 70%. Thus, the pore size distribution is improved. The hydration degree also increases to more than 0.6. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) show that the hardened paste in concrete is densified, the amounts of aligned needle-shaped ettringite and plate-shaped Ca(OH)2 are reduced, and the bonding property of interfacial transition zone (ITZ) is improved by vacuum water-removal and compression. The machine-made sand concrete fabricated by vacuum water-removal and compression is in line with the developing trend of green, energy saving and environmental protection for the production of modern pre-cast concrete members.

In order to master the brittleness characteristic of steam cured concrete, the effects of curing temperature (20, 45, 55, 65, 75 ℃)and mineral admixtures on brittleness of concrete were studied by using brittleness coefficient and impact toughness as evaluation indexes, and the effects of curing temperature and mineral admixtures on the microstructure of hydration products and pore structure of the concrete were analyzed by scanning electron microscope and mercury porosimeter. The results show that the brittleness coefficient of the steam cured concrete increases with the increase of curing temperature or curing age, and the steam curing reduces the impact toughness of concrete. When two mineral admixtures of fly ash and granulated blast furnace slag (GBFS) powder are added into concrete mixture, the brittleness coefficient and impact resistance of the steam cured concrete are improved. Higher curing temperature leads to coarse crystallization of hydration products, formation of micro cracks in the interface transition zones and increment of porosity of concrete matrix, which increases the brittleness of steam cured concrete. Fly ash and GBFS improve the pore structure and microstructure of the interface transition zone of steam cured concrete.

To address the problem of shear damage along the mortar joints of raw soil masonry walls under seismic action due to the low strength of masonry mud, the ecological modification formulas of raw soil mud to improve the shear strength of masonry were proposed without destroying the return to the field of raw soil. The effects of the dosages of glutinous rice glue, acrylic emulsion, instant glue powder and cellulose on the shear strength, compressive strength and flexural strength of raw soil mud were investigated by single-factor and orthogonal tests, and the optimal mix ratio of modified mud was obtained. Then the return to the field analysis of modified raw soil material and the shear test of raw soil masonry were carried out. The research results show that compared with the traditional unmodified mud, the shear strength of modified mud increases by 50.55%, the compressive strength increases by 33.14%, and the flexural strength increases by 23.48%. The modified raw soil material can make crops grow normally, the soil composition analysis conforms to the plant planting standard, and its return to the field is not damaged. The shear strength of raw soil masonry with modified mud increases by 34.77% compared with the unmodified raw soil masonry.

Nitrogen oxides are the one of major air pollution. Selective catalytic reduction (SCR) is the main technical way of high-efficiency DeNOx of industrial boiler (kiln) flue gas at home and abroad. The DeNOx catalyst is the core of SCR technology, which has been concerned and widely studied in recent decades. Metal oxide catalyst has a broad application prospect in industrial boiler (kiln) flue gas DeNOx, wide range of material sources, simple preparation and stable DeNOx efficiency, and it becomes the focus of research attention. Based on the current situation of SCR flue gas DeNOx theory, the key and important basis for the optimal design of metal oxide catalysts were summarized. At the same time, the research progress of four typical metal oxide catalysts, such as vanadium, manganese, cerium and iron, was reviewed. The DeNOx mechanism, essential characteristics, element improvement, structure and morphology design and existing problems of different oxide catalysts were introduced systematically, and the development trend of metal oxide catalysts in the future was prospected. It would provide reference for the research of efficient DeNOx catalyst for industrial boiler (kiln) flue gas.

CO2 capture technology is an important way to deal with global climate change and mitigate the greenhouse effect. The preparation of efficient CaO-based CO2 capture materials from calcium-containing solid wastes is conducive to the realization of high-value utilization of solid wastes, waste treatment and clean production, which has important environmental benefits, economic benefits, and social benefits. Based on the good application prospects of efficient and cheap CaO-based CO2 capture materials from solid wastes, the production and resource utilization of industrial waste residues, biomass and other calcium-containing solid wastes were introduced in this paper. The capture principle, carbonation kinetic process and CO2 capture performance of CaO-based adsorbents were summarized. The adsorption-desorption cycle performance of CaO-based adsorbents prepared with different calcium-containing solid wastes as precursors and the influences of different modification methods on the adsorption stability of CaO-based adsorbents were compared. The potential applications of CaO-based adsorbents from solid waste in steel plants, coal-fired power plants and bio-hydrogen production were analyzed from an economic point of view. The application prospect and development direction of CaO-based CO2 capture materials from solid wastes were prospected. The purpose of this paper is to provide help for the selection of CaO-based adsorbent precursor from solid wastes, the improvement of adsorption performance and the industrial application of solid waste adsorbents.

The cement production in China is mainly based on the new dry cement kiln technology. The fuel used in cement production is bituminous coal with high volatile and low ash. Cement production is a high energy consumption and high emission industry. Controlling energy consumption and reducing carbon emission in cement production process is of great significance to achieve the goal of "double carbon". Coal combustion catalysts can effectively solve the problem of high energy consumption and high emission in cement production process, which has attracted wide attention in recent years. Based on the domestic and foreign research status, the composition and evaluation methods of coal combustion catalysts, the catalytic mechanism of catalysts, the research of desulfurization and denitrification coal combustion catalysts, and the application of catalysts in industrial production were systematically reviewed. Researching and improving the catalyst adding method and ensuring the dispersion in pulverized coal can improve the catalytic efficiency of the catalyst, which is the key to promote the industrial application of coal combustion catalysts.

With the utilization of solid waste resources becoming a hot topic nowadays, the research outputs of autoclaved aerated concrete prepared by solid waste are endless in recent years. However, due to the wide variety and different characteristics of solid wastes, the laws and mechanisms of solid wastes affecting the dry density, compressive strength and other key properties of autoclaved aerated concrete are not clear, which need to be summarized urgently. This paper first summarized the main factors affecting the dry density and compressive strength of autoclaved aerated concrete in terms of matrix and pore structure, and then analyzed the rules and mechanisms of solid wastes influencing the dry density and strength of autoclaved aerated concrete in terms of siliceous, calareous and gassing materials, finally summarized the problems in the current research and discussed the future research directions.

Granite has excellent characteristics, such as high strength, high hardness, low water absorption, good chemical stability, strong durability and beautiful colour, therefore it is widely used in the preparation of high-quality building stone. However, the cutting production process of granite produces a large amount of saw mud, occupying a great quantity field and polluting the environment. Based on the current situation of granite saw mud stockpiles and the hazards, the main treatment methods of granite saw mud were introduced, the most common reutilization ways of granite saw mud were discussed, the application and development of granite saw mud in glass-ceramics, foamed ceramics, ceramic glazes and aerated concrete block were summarized, providing references for the efficient use of granite waste in the field of construction materials.

Soft soil foundation treatment is an engineering field with high risk recognized by the engineering community. The large amount of Portland cement used in traditional soft soil stabilized not only consumes natural resources, but also has adverse effects on the environment. The use of environment friendly alkali-activated geopolymers to replace traditional Portland cement has attracted more and more attention. Based on the existing research results at home and abroad, the research progress from the historical development of alkali-activated geopolymer solidified soil, types of alkali-activated geopolymers, reaction mechanism of alkali-activated geopolymer, mechanical properties and various properties of alkali-activated geopolymer solidified soil were summarized and analyzed. The mechanical properties of soft soil treated by geopolymer were mainly discussed. At the same time, the impermeability, freeze-thaw resistance and corrosion resistance of different alkali-activated geopolymers in soft soil foundation reinforcement were also analyzed and studied. The application in soft soil foundation reinforcement is systematically reviewed and prospected, in order to guide and improve the application of alkali-activated geopolymers in soft soil foundation reinforcement, and realize the sustainable development of foundation reinforcement in China.

The mechanical properties of fiber reinforced composites are mainly affected by fiber properties, resin properties, and composite interface properties between fiber and resin. In practical application, fiber surface modification is the key to strengthen the binding force between fiber and matrix and expand the application field. In this paper, several modification methods of basalt fibers at home and abroad were reviewed. The mechanism and effects of various surface modification methods were summarized, and the properties and applications of basalt fiber were briefly introduced. The results show that the surface activity, strength and interface binding strength of basalt fiber after modification are improved, which is conducive to the preparation of composites with excellent performance, so as to be used in the fields of civil construction, environmental protection, automobile and ship, aerospace and etc. In addition, the main problems existing in the field of basalt fiber modification were pointed out and the future research direction of this field was prospected.

The coal gangue aggregate was pretreated by slurry wrapping technology. The water absorption, crushing value and deterioration behavior under dry-wet and freeze-thaw environment of original coal gangue aggregate and different slurry wrapped coal gangue aggregates were studied. The strength and durability of slurry wrapped coal gangue concrete were tested and the correlation between aggregate performance enhancement and concrete performance improvement was analyzed. XRD and SEM were used to analyze the mineral composition, microstructure and interfacial transition zone of original coal gangue aggregate and slurry wrapped coal gangue aggregate before and after dry-wet and freeze-thaw cycle. The results show that the original coal gangue aggregate has high water absorption, low hardness and obvious deterioration in dry-wet and freeze-thaw environment, while the performance of coal gangue aggregate is improved after slurry wrapping. The strength and durability of original coal gangue concrete are poor, while the performance of coal gangue concrete is enhanced after slurry wrapping. The correlation between the performance of aggregate and concrete is good. The main reason for the deterioration of coal gangue aggregate is that clay minerals soften and destabilize under dry-wet and freeze-thaw environment after absorbing water, but the wrapping slurry can isolate water, thus strengthening the performance of aggregate. Aggregate strengthening and the improvement of the bonding degree between aggregate and mortar matrix jointly promote the performance improvement of slurry wrapped coal gangue concrete.

In order to investigate the chloride ion permeability resistance of lithium slag concrete under pressure circumstance, C20, C30 and C40 concrete with different content of lithium slag (0%, 10%, 20% and 30%, mass fraction) were designed in this paper. It applied 10%, 30% and 50% of the ultimate compressive load as continuous compressive stress to carry out the concrete chloride ion permeability tests. The results show that the electric flux increases with the increase of water-cement ratio when the water-cement ratio is in the range of 0.40 to 0.62. For the concrete with different stresses applied, the electric flux of C20 and C30 concrete increases significantly when the compressive stress ratio reaches 0.3, and the electric flux of C40 concrete increases significantly when the compressive stress ratio reaches 0.5. For the concrete with different lithium slag content, the electric flux decreases with the increase of lithium slag content. Taking Fick’s second law and the law of conservation of mass into consideration, the model of chloride ion permeability of lithium slag concrete was established under continuous load. The results show that the permeability of chloride ion in immersion environment is in accordance with the experimental law, and the simulation results are consistent with the experimental results as well.

To promote the harmless treatment and resourceful use of steel slag, making steel slag into powder instead of quartz powder to prepare ecological ultra-high performance concrete (UHPC) is one of the effective ways to reuse it. To address the issue of the influences of raw material factors in the formulation of steel slag powder UHPC, the strength indicators of steel slag powder UHPC such as compressive strength, flexural strength, splitting tensile strength and elastic modulus were tested under different mix proportion using orthogonal test method, so as to analyze the effect of silica fume content, steel slag powder content, river sand content and steel fiber content on their various performance indicators. The test results show that the volume content of steel fiber has the most significant effect on the mechanical properties of steel slag powder UHPC, while the content of river sand and steel slag powder has a greater effect and the content of silica fume has a smaller effect. The order of significance in the indexes of cubic compressive strength, flexural strength and static compressive elasticity modulus is steel fiber>river sand>steel slag powder>silica fume. The order of significance in the indexes of axial compressive strength and splitting tensile strength is steel fiber>steel slag powder>river sand>silica fume. The optimum mix proportion scheme is obtained by orthogonal test, and the steel slag powder UHPC prepared according to this scheme has good working performance and mechanical properties.

As the waste residue generated in the process of aluminum recycling, the secondary aluminum ash has obvious chemical reactivity, leaching toxicity of toxic and harmful substances and other dangerous characteristics. In order to solve the problem of stockpiling and disposal of secondary aluminum ash generated in aluminum industry, the secondary aluminum ash was used as raw material to prepare high strength ceramsite through water washing, disk granulation and 1 200~1 400 ℃ heat treatment. The phase composition and micromorphologies of the ceramsite samples sintered at different temperatures were analyzed by X-ray diffractometer and scanning electron microscopy. The bulk density, apparent density, porosity and cylinder compressive strength of the ceramsite were tested. The results show that with the increase of heat treatment temperature, the internal structure of ceramsite becomes denser gradually, and the bulk density, apparent density and cylinder compressive strength increase. The main phases of ceramsite after heat treatment at 1 400 ℃ are corundum and magnesia alumina spinel. The apparent density, volume density and cylinder compressive strength of ceramsite are 182 g/cm3, 1.81 g/cm3 and 25.7 MPa, respectively, meeting the requirements of high strength ceramsite.

In order to realize the resource utilization of industrial by-product phosphogypsum, based on the central composite design method in response surface method, sulfoaluminate cement (SAC) and protein retarder (SC) content were selected as variables to optimize the performance of hemihydrate phosphogypsum cementitious material (HPCM) and prepare high performance HPCM. The response surface curves of relationship between the variables and 1 d compressive strength, dry compressive strength, initial setting time and final setting time were obtained through data processing, and the corresponding response surface models were established. The results show that the optimal mass content of SAC and SC is 20.48% and 0.12%, respectively. The dry compressive strength of HPCM is 23.1 MPa and the initial setting time is 38 min. The mechanical properties and working properties of HPCM are good. Based on the analysis of the hydration process and the composition of hydration products, it is mainly that the change of mineral phase leads to the generation of new hydration products, which improves the microstructure of the system, so as to optimize the performance.

In order to improve the utilization rate of graphite solid waste, this paper used graphite mining waste stone as fine aggregate, added spherical graphite tailing and waste stone stone powder with different mass fraction to carry out an experimental study on the formula of electrothermal plate. The influences of graphite mining waste stone replacement and stone powder content on the performance of electrothermal plate were explored. The results show that using 100% (mass fraction) graphite mining waste stone as fine aggregate, the bending strength and compressive strength of cement plate maintained for 28 d are 11.09 MPa and 50.90 MPa, respectively. Although they are slightly lower than the strength index of cement plate using standard sand, but they meet the relevant requirements. This shows that graphite mining waste stone can be used as fine aggregate. When waste stone stone powder content is 7% (mass fraction), the bending strength and compressive strength of electrothermal plate reach up to 6.21 MPa and 33.00 MPa. Although the strength is reduced, it can still meet the requirements of low-strength plate. When spherical graphite tailing content is 9% (mass fraction), the volume resistivity of electrothermal plate is 1.94 Ω·m, and the heating temperature is 71 ℃, which has a good electrothermal effect.

In view of special engineering properties of red clay and the waste of phosphogypsum solid-waste resource, the compression characteristics of phosphogypsum-stabilized red clay under different mixing ratios were studied through consolidation tests with cement as curing agent. And the mechanism of compressive modulus change law was analyzed based on microstructure and mineral composition. The results show that plain red clay presents medium compressibility, while phosphogypsum-stabilized red clay presents medium and low compressibility. The compressive modulus of mixture increases first and then decreases with the increase of phosphogypsum content. The compressive modulus is the largest as the mass ratio of cement to phosphogypsum is 1∶3. The degree of influence on the compressive modulus of mixture is vertical load>cement content>phosphogypsum content. The compressive modulus of mixture can be fitted by a binary cubic function relationship with cement content and phosphogypsum content. With the increase of phosphogypsum content, the hydration reaction, adsorption of cement and the formation of ettringite reduce the porosity of the mixture. When the mass ratio of cement to phosphogypsum is 1∶3, the porosity is minimum. When the content of phosphogypsum continues to increase, the solution is acidic, ettringite is dissolved, the content of free iron oxide decreases, the cementation and mechanical bite of aggregates are reduced, and the compression modulus is reduced.

Zirconium silicate encapsulated carbon (C@ZrSiO4) black pigment was prepared by sol-precipitation method, using walnut shell powder, zirconium oxychloride (ZrOCl2·8H2O) and ethyl silicate (TEOS), etc. as raw materials. The heat effect, chemical structure, phase composition and microstructure of samples were investigated by TG-DSC, FT-IR, XRD, SEM and TEM.The effects of different heat treatment temperatures and mass ratios of walnut shell powder/ZrSiO4(theoretical synthesis, the same below) on the phase composition and chromaticity value of pigment were studied. The results show that the C@ZrSiO4 pigment with excellent coloring performance (L*=31.3, a*=+1.4 and b*=+1.3) can be obtained when heat treatment temperature is 1 100 ℃, and the mass ratio of walnut shell powder/ZrSiO4 is 1∶3. When 5% (mass fraction) C@ZrSiO4 is added to transparent glaze under firing temperature of 1 200 ℃, the black glaze exhibits excellent coloring performance with the color value of L*=41.2, a*=+1.2 and b*=+1.7.

In order to improve the mechanical properties of recycled aggregate concrete (RAC), waste polyethylene terephthalate (PET) plastic bottles were shredded into fiber strip to prepare fiber reinforced recycled aggregate concrete (FRRAC). A series tests like slump test and strength test on FRRAC, together with RAC as reference, were performed to investigate the effects of length and content of waste PET plastic fibers on FRRAC properties. Furthermore, the significance analysis of strength influencing factors and microstructure analysis of concrete were conducted. The results show that, compared with RAC, there is a reduction in the fludity of FRRAC with the increase in length and content of waste PET plastic fibers. The compressive strength overall increases, and the splitting tensile strength significantly increases with the addition of PET fibers in RAC. The content of fibers shows significant effect on compressive strength. As for splitting tensile strength, significant effects of length and content as well as their interaction are all exhibited. Although the incorporation of PET fibers into RAC leads to weak interface transition zones, the microstructure of FRRAC is denser than RAC.

The special structure and mineral composition of loess lead to its easy disintegration in water, and lead to a series of geotechnical engineering problems such as slope instability and collapsible settlement. Microbially induced calcite precipitation (MICP) technology is a new microbial mineralization technology. In this paper, the effects of curing age and cementing fluid concentration on the disintegration time and disintegration rate of MICP modified loess were investigated by means of self-made disintegration instrument. Based on the single value effective stress formula of unsaturated soil, the mechanical model of unsaturated soil disintegration was established from the view of pore water pressure and pore air pressure. The disintegration rate-time formula was used to fit the disintegration curves of loess samples. The results show that the disintegration rate of MICP modified samples are lower than unmodified samples. With the increase of curing age, the disintegration time of 0.6 mol/L cementing liquid modified loess increases from 12 min to 28 min. After curing for 14 d, the disintegration rate of MICP modified loess reaches the lowest value of 0.02%, and the adjusted goodness of fit of the disintegration rate-time formula to disintegration rate curve is above 0.90.

Ultra-high temperature ceramics and their composites have become the focus and frontier of thermal structural materials research in the field of aerospace because of their advantages of ultra-high temperature resistance, lightweight and anti-oxidation ablation. Based on the excellent performance and successful application of rare earth compounds in thermal barrier coatings and other fields, researchers have introduced rare earth compounds into ultra-high temperature ceramics and their composites to improve the structure and properties of oxide layer in order to solve the problems of rapid growth of oxide layer of ultra-high temperature ceramic matrix composites and easy spalling of high and low temperature circulating oxygenation layer in a wide temperature range. This paper summarized the research status of rare earth modified ultra-high temperature ceramics and their composites, analyzed and discussed the modification mechanism, and looked forward to the future research and development direction.

Combined with the excellent mechanical properties, chemical stability and white aesthetics, zirconia ceramics have been widely used in the teeth-related restorations in dentistry, such as crowns, bridges, abutments and more recently implants. However, the biosafety of zirconia ceramics has been jeopardized by the low-temperature degradation (LTD). LTD phenomenon occurs at low temperatures and humid environments, e.g. in human bodies, the strength of zirconia ceramics decreases rapidly in the short term, which leads to early failure. In this paper, the research on LTD phenomenon of zirconia ceramics by scholars from various countries in recent years was reviewed from the perspectives of characterization methods, influencing factors and degradation theoretical models, and the related research results were sorted out and summarized.

Stereo light-cured apparatus technology is an emerging additive manufacturing process for producing high-precision and high-performance ceramic parts. The preparation of ceramic slurry with good flowability and high solid phases content is the advantage to stereo lithography apparatus additive manufacturing. The influences of solid phase content, monomers, dispersants, powder gradation and other factors on the rheological properties of the slurry were disscussed, and the current material selection principles for the preparation of light-cured Al2O3 ceramic slurry with high solid phase content and low viscosity were summarized. The guiding methods for preparing light-cured Al2O3 ceramic slurry with high solid phase content and low viscosity were summarized, and the main trends and challenges in the development of high performance photocurable Al2O3 ceramic slurry were pointed out.

The photosensitive resin system affects the shrinkage rate in the molding process of the photocurable 3D printing ceramic components and the stress in the degreasing process. In this paper, three resin systems, including the monofunctional resin with ring structure, the trifunctional resin and the multi-component resin with the introduction of prepolymer and diluent, were designed. The shrinkage rate of the three resin systems was tested. The research shows that the resin system with the introduction of prepolymer and diluent has the lowest curing shrinkage rate, which effectively alleviates the problem of cracking of 3D printed alumina ceramic blank caused by curing reaction shrinkage. The thermal decomposition behavior of three resin systems was studied by thermogravimetric analysis and heat treatment experiments. The multi-component resin system has the characteristics of staged pyrolysis. The photosensitive aluminum oxide slurry was prepared by using this resin system, and the photocuring printing parameters and degreasing atmosphere were optimized. The 3D printing thick wall solid (12 mm×12 mm×12 mm) samples and large sizes (80 mm×50 mm) aluminum oxide ceramic green body are both degreased without cracks.

As the core part of Al-air batteries cathode, the catalytic performance of electrocatalyst affects the industrialization process of Al-air batteries. In this work, nitrogen-doped carbon material (N/VC2) was prepared through urea high temperature treatment method based on commercial Vulcan-72XC carbon material. Mn3O4@N/VC2, MnO@N/VC2 and MnO2@N/VC2 composites were further obtained by loading different manganese oxides. MnO2@N/VC2 displays the superior oxyen reduction reaction (ORR) performence with the positive onset potential of 0.872 V. In addition, Al-air battery based on MnO2@N/VC2 shows excellent discharge performance in high current density, and the maximum power density can reach 136 mW·cm-2. The interaction between carbon carrier and manganese oxide was studied by comparing the electrocatalytic properties of different composites. The results show that the synergistic action of porous structure and abundant defect sites is the main reason for improving the catalytic activity of the material. This work provides a theoretical basis for the research and development of manganese-based oxide catalysts.

Yunnan province is rich in mineral resources, and albite is one of the local dominant minerals. However, at present, the industrial application area of albite is simple and the addtional value of products is low. In this paper, Yunnan albite was used as the raw material, and albite ceramics were prepared by digital light processing (DLP) technology. The effect of sintering temperature on the properties of albite ceramics was investigated, and albite ceramics with complex structure were successfully prepared based on the research results. The results show that the forming effects of albite ceramics prepared by DLP are good, and the bending strength of albite green body is 18.30 MPa. With the increase of sintering temperature, the main phases of albite ceramics are albite and anorthite, and there are not other phases. The shrinkage, densification degree and bending strength of albite ceramics increase gradually. When the sintering temperature reaches 1 150 ℃, the shrinkage of the albite ceramics is the largest, 35.25% (Z direction). Meanwhile, the microstructure of albite ceramics is dense, the mechanical property is satisfactory, and the bending strength is 98.69 MPa. It has important effect on promoting the industrial development of Yunnan albite that combining Yunnan albite with DLP technology to prepare high-performance albite ceramics with complex structure.

Lead zirconium titanate (PZT) films were deposited on Pt/Ti bottom electrode by magnetron sputtering process. The influences of in-situ annealing temperature and electrode deposition temperature on crystal orientation, microstructure, dielectric, ferroelectric, and fatigue characteristics of sputtered PZT films were studied. The results of X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis show that as the electrode deposition temperature increases, the Pt crystal grain size increases, and as the annealing temperature increases, the PZT film compactness becomes worse. The Pt/Ti bottom electrode prepared at room temperature after in-situ annealed in 200 ℃ for 30 min can easily promote the (100) orientation of the PZT film, while the Pt/Ti bottom electrode prepared or annealed at high temperature is more conducive to the (111) orientation. The best dielectric property is obtained in the PZT film according to electrical tests, in which the Pt/Ti bottom electrode is prepared at room temperature and in-situ annealed in 200 ℃ for 30 min. And the PZT film exhibits high residual polarization strength and minimum coercive field strength. After 108 times polarization inversions, the initial polarization of the film drop is only 11%.

Bischofite is a very promising magnesium salt resource with abundant reserves and low cost. Magnesium silicate hydrate (M-S-H) gels with different MgO/SiO2 molar ratios (0.5∶1, 1∶1, 1.5∶1) were synthesized using bischofite from Qinghai Salt Lake and sodium silicate. The synthesis mechanism and structural characteristics of M-S-H were studied by XRD, SEM, infrared, and nuclear magnetic resonance tests. Then, the synthesized M-S-H was compounded with microsilica to prepare magnesia castable, and the influence of M-S-H structure on the bonding characteristics of castable was explored. The results show that M-S-H obtained from different MgO/SiO2 molar ratios exhibits a layered stacking structure. When the MgO/SiO2 molar ratio is 1∶1, the interlaminar free water is the least and the crystallinity is the highest. The synthesized M-S-H is used to replace part of microsilica to prepare magnesia castable, which significantly improves the mechanical properties of the castable after heat treatment at 1 550 ℃. The magnesia castable prepared with M-S-H (MgO/SiO2 molar ratio of 1∶1) and microsilica obtains the best comprehensive properties. Compared with the magnesia castable prepared by adding 6% (mass fraction) microsilica, the flexural strength at room temperature and high temperature increases by 75% and 8%, respectively.

Steel slag corrosion is one of the main damage forms of refractory during service, and it is hard to observe the actual corrosion process directly. Traditionally, postmortem analysis is used to evaluate corrosion resistance capacity and to understand corrosion mechanism of refractory. However, the lack of process information in postmortem analysis results in deviation. Therefore, on the basis of high temperature visualization system and digital image correlation (DIC) method, three typical steel slags were selected to carry out the corrosion corrosion behavior experiments of alumina magnesia refractory, and the effects of different steel slags and heat treatment temperatures on the corrosion resistance capacity of refractory were discussed. The results show that the slag with lower basicity has more serious corrosion on refractory. The corrosion resistance capacity of alumina magnesia refractory can be effectively improved by heat treatment above 1 000 ℃. The average strain curve and corrosion strain nephogram over time can be obtained through DIC method. The average strain curve is used to compare the corrosion resistance capacity of alumina magnesia refractory to different steel slags, and the corrosion strain nephogram reflects the evolution process of corrosion. The above two provide quantitative indicators for characterizing the slag corrosion process of refractory.