The invention of superfine cement is mainly to solve the problem that particles size of ordinary cement are too large to effectively inject into fine cracks. Superfine cement combines the good durability of ordinary cement and the high fluidity of chemical grouting materials. It has become an important beginning for cement-based materials to change from traditional materials to high-tech materials, which is widely used in engineering. The main progress made by scholars at home and abroad in the research of superfine cement in the past 20 years was reviewed and summarized. The production technology of dry grinding and wet grinding and their advantages and disadvantages were compared and analyzed. The rheology, volume stability and mechanical properties of superfine cement compared with those of ordinary cement were compared. Furthermore, the influences of the addition fly ash, mineral powder and other admixtures on the performance of superfine cement slurry were summarized. On this basis, the application of superfine cement in reinforcement and plugging technology was summarized, aiming to provide relevant references for the production process, basic properties and related engineering applications of superfine cement.

With the attention paid to the sewage system planning by the country, concrete has been widely used in sewage pipes. During the service period of sewage pipelines, concrete will be subjected to the synergistic effects of physics, chemistry and biology, leading to its deterioration. Among many corrosive media, sulfuric acid has the most prominent impact on the performance of concrete. In order to further deepen the understanding of this research field, this paper mainly introduces the research progress from the sources of sulfuric acid in sewage pipes, the mechanism of sulfuric acid corrosion of concrete, the factors affecting sulfuric acid corrosion, and the countermeasures against sulfuric acid corrosion, and looks for effective anti-corrosion measures for sewage pipe concrete.

Based on the structural reconstruction ability of layered double hydroxides (LDHs), the nitrite intercalated LDHs were prepared. In this paper, nitrite intercalated LDHs was added into cement as a new type of chromium reducing admixture. Reduction efficiency, resistance to storage and stability under ball milling temperature conditions of nitrite intercalated LDHs were investigated. The mechanism of reduction and solidification of soluble Cr6+ in cement using nitrite intercalated LDHs was revealed. The results show that nitrite ions released from LDHs-NO2 interlayer mixing with water rapidly reduce soluble Cr6+ and effectively decrease soluble Cr6+ content in cement. The addition of 0.2%(mass fraction) LDHs-NO2 reduces the soluble Cr6+content in cement from 40.26 mg/kg to 9.36 mg/kg, and improves the compressive strength of cement by about 2 MPa. The reduced Cr3+ exchanges with Al3+ into LDHs laminate to achieve stable chemical solidification. The reduction efficiency of synthetic nitrite intercalated LDHs is better than FeSO4·7H2O. Furthermore, synthetic nitrite intercalated LDHs remains reductive stability when the cement is stored for a period and treated at ball mill temperature.

At the initial stage of cement hydration under geothermal environment, the monosulfoaluminate (AFm) and sulfate are easy to form delayed ettringite (DEF)in the pores or interfaces, which will lead to expansion and cracking of concrete. The solution method was used to simulate the temperature humidity coupled liquid environment of ettringite (AFt) formation, the molecular dynamics simulation method was used to study the internal structure change of AFt under normal temperature and geothermal environment, and the formation temperature limit of DEF and the critical gypsum content in cement were determined. The results show that the geothermal high temperature environment will affect the growth of AFt crystals on (100) and (110) crystal planes, leading to the gradual decrease of AFt formation with the increase of temperature. 70~75 ℃ is the key temperature range for the transformation of AFt to AFm, but AFt can still be formed in the liquid phase environment above 75 ℃, and transformed AFm content will gradually increase with the increase of temperature. High temperature can promote the formation of AFt hydrated at early stage of cement. With the increase of curing age, high temperature will cause that AFt generated at early stage to gradually transform into AFm. Forming amout of AFt in concrete increases with the increase of gypsum content, and gypsum with a mass fraction of about 4% is the appropriate content. The molecular dynamics simulation results also show that AFt structure is stable at room temperature, but its structure changes under geothermal conditions.

Ferrite phase solid solution(hereinafter ferrite phase)is an important mineral in ferroaluminate cement clinker, but its effect on the sintering and properties of ferroaluminate cement clinker is not completely clear. The formation of ferroaluminate cement clinker with different ferrite phase content was studied by comprehensive thermal analysis, burnability analysis, X-ray diffraction and petrographic analysis methods. The results show that the increase of ferrite phase content has no significant effect on the endothermic and exothermic reaction temperature during the formation process of ferroaluminate cement clinker, but it makes liquid phase content increase obviously during the sintering process of clinker. The increasing of ferrite phase content has a hindering effect on the formation of C4A3 during the formation process of ferroaluminate cement clinker, but it promotes the sintering of clinker and the growth of clinker mineral crystals. In the formation process of ferroaluminate cement clinker, the transition minerals C5S2 disappear completely when the calcination temperature up to 1 250 ℃. When the calcination temperature up to 1 350 ℃, a large amount of C4A3 will decompose. The suitable sintering temperature range is 1 250~1 350 ℃.

The use of hydroxylated graphene (HO-G) modified cement-based permeable crystalline waterproof materials (CCCW) not only improves the mechanical properties of whole structure, but also reduces the cost to a certain extent. The effect of sodium lignosulfonate(SL) on the dispersion performance of HO-G was studied, and the influence of HO-G on the mechanical properties of CCCW was studied. The results show that when the mass ratio of HO-G to SL is 1∶4, HO-G has the best dispersion performance in Ca(OH)2. When HO-G content is 0.03% (mass fraction), compared with benchmark specimen, the 3 and 28 d compressive strength of HO-G mortar specimen increases by 3769% and 3305%, respectively and the 3 and 28 d flexural strength increases by 17.31% and 31.52%, respectively. The impermeability pressure ratio of CCCW coating specimens modified by HO-G is 127 percentage points higher than that of CCCW coating specimens alone. SL promotes the dispersion of HO-G in cement-based materials, and HO-G plays a filling role and template role in mortar matrix, which enhances the compactness of hydration products, and then improves the mechanical properties of material.

The modified CaAl-LDHs corrosion inhibitor (CaAl-EDTA LDH) was prepared by calcination reduction method with EDTA-2Na as modifier, and the effect of CaAl-EDTA LDH on the macro-properties (fluidity, setting time, mechanical properties) and micro-properties (product composition, hydration heat, pore structure) of cement-based materials was investigated. Besides, two corrosion modes were set up to simulate the protective effect of CaAl-EDTA LDH with different content (0%, 0.5%, 1.0%, 2.0%, 4.0%, mass fraction) on the embedded reinforced mortar specimens. The results show that the addition of 0.5% and 1.0% CaAl-EDTA LDH promotes the dissolution of cement minerals, increases the hydration heat release, and improves the early strength of mortar. However, EDTA has a retarding effect. When the content of CaAl-EDTA LDH is 4.0%, the hydration heat release and the formation of early hydration products of mortar seriously reduces, while the paste total porosity of 28 d increases by about 4%. Moreover, corrosion test results indicate that CaAl-EDTA LDH does not show corrosion resistance in dry-wet cycle mode, while it shows excellent corrosion resistance on reinforcement in mortar after 90 times dry-wet cycle under dual corrosion mode with the content controlled in 1.0%~2.0%. The new type of corrosion inhibitor in this paper has reference significance for prolonging service life of reinforced concrete and improving durability of structures.

The pseudo-static test of 7 PVA-FRCC medium-length columns (hereinafter PVA-FRCC columns) was carried out with the shear span ratio, reinforcement ratio, and axial compression ratio as the research variables, and the crack morphology, deformation, energy consumption, and laser damage resistance of PVA-FRCC medium-length columns under seismic action were investigated. The results show that PVA-FRCC columns exhibit excellent crack control ability and closure ability after unloading, as well as remarkable ductility, deformation, and energy consumption capacity, with a maximum elastic-plastic limit displacement angle of 1/13. Specimens with higher shear span ratios have lower bearing capacity, while the reinforcing effect of PVA fibers endows superior deformation resistance and damage resistance after peak load. Furthermore, an increasing of reinforcement ratio leads to improve bearing capacity, deformation, and damage resistance of the PVA-FRCC columns, while an increasing of the axial compression ratio significantly reduces deformation, energy consumption, and damage resistance of specimens. PVA-FRCC columns with a smaller axial compression ratio and an appropriate shear span ratio and reinforcement ratio exhibit optimal performance when the PVA fiber volume fraction is 1%. To evaluate the damage status of PVA-FRCC columns, an improved Park-Ang damage model is proposed, which well satisfies the boundary conditions and reflects the trend of damage development which consistent with experimental results.

Engineering cementitious composites(ECC)have good ductility and tensile properties. However, the molding shrinkage rate of ECC is large, which leads to cracking in the molding process of specimens and seriously affects the durability of structure. High performance calcium sulpho aluminate(HCSA)expansion agents were added into ECC to reduce the molding shrinkage rate, and the influences of different expansion agents content on the molding shrinkage rate and mechanical properties of ECC were investigated. The results show that the shrinkage rate of ECC can be improved significantly when expansion agents content is 6%~8% (mass fraction same below), but excessive expansion agents will cause expansion of ECC. The compressive strength of ECC significantly increases and there is little change in the tensile strength when expansion agents content is 4%~6%. The shear toughness of ECC significantly increases and there is little change in the shear strength when expansion agents content is 2%~4%. The maximal flexural strength of ECC significantly increases when expansion agents content is 6%~8%.

C125 ultra high performance grouting materials for offshore wind power were prepared by using azo compound plastic expansion agent (PEA1) and nitroso compound plastic expansion agent (PEA2), respectively. The effects of the type and content of plastic expansion agent on the fluidity, expansion rate, compressive strength, electric flux and pore structure distribution of C125 ultra high performance grouting materials for offshore wind power were studied. The results show that with the increase of plastic expansion agent content, the fluidity of grouting materials increases first and then decreases, the compressive strength decreases gradually, and the vertical expansion rate and electric flux increase gradually. Compared with PEA2, PEA1 has greater influence on the fluidity, compressive strength, vertical expansion rate and electric flux of grouting materials at the same content. The total void fraction, average pore diameter and large pore proportion of grouting materials with PEA1 increase more obviously than that of grouting materials with PEA2 at the same content.

A new method of coating and surface hydrophobic modification was proposed to treat artificial aggregate aiming at solving the problems of loose and porous surface of artificial aggregate and insufficient binding with cement paste in concrete. Different mass fractions of silane coupling agent solution and silicone resin were used to modify the artificial aggregate of carbonation curing. The effects of modification methods on the water absorption rate, particle strength of artificial aggregate and bond strength of aggregate-cement mortar were studied, and the microstructure of artificial aggregate and the interface morphology between artificial aggregate and cement mortar before and after modification were characterized by meso/micro test analysis methods. The results show that compared with the single use of chemical solution to modify artificial aggregate, the combined modification method significantly optimizes the surface microstructure of artificial aggregate and improves the aggregate performance, and the water absorption rate of aggregate is reduced to 1.74%. When the mass fraction of silane coupling agent is 5%, a modified layer with appropriate thickness is formed on the surface of artificial aggregate, and the binding property between artificial aggregate and cement mortar is significantly improved.

Aqueous dispersion emulsion of phase change paraffin was prepared and mixed into chemical foaming process to prepare phase change foamed concrete. The dry density, compressive strength, volumetric water absorption, thermal insulation property, phase change stability and microcosmic state of phase change foamed concrete were tested by experiments. The results show that the phase change paraffin emulsion has adverse effects on the chemical foaming process and compressive strength of material. Phase change foamed concrete can be stably made when the amount of phase change paraffin emulsion is less than 40% of dry powder in quality. Phase change paraffin is dispersed in foamed concrete matrix in the form of tiny particles. The compressive strength of foamed concrete decreases by 35%~47%, and the volumetric water absorption decreases by 19%~30% when the phase emulsion is 40% of dry powder. Phase change paraffin can improve the thermal insulation property of foamed concrete in a certain temperature range. The phase change stability is good, and the paraffin is difficult to leak.

In response to ensuring the rapid opening and post-opening life of existing traffic lines rehabilitation, ultra-high performance concrete (UHPC) was developed with sufficient construction time and super-early-strength (reaching open strength within several hours). Based on the UHPC mixture proportion designed via maximum compactness theory, the effect of the substitution rate of ordinary Portland cement (OPC) on the mechanical performance and workability of sulphoaluminate-ordinary Portland cement system (SAC-OPC system) concrete was studied via experiments, and the OPC substitution rate was determined. Super-early-strength UHPC with initial setting time of 36 min and 3 h compressive/flexural strength of 414/170 MPa and super-early-strength UHPC with initial setting time of 40 min and 3 h compressive/flexural strength of 362/13.9 MPa are prepared via the orthogonal tests on the mechanical performance and workability of SAC-OPC system concrete with early strength agents (lithium sulphate, aluminum sulphate), enhancing agents (nano calcium carbonate) and slow-setting agents (slow-setting powder, sodium tetraborate). The mechanism for the performance formation of super-early-strength UHPC with sufficient construction time was studies by SEM and XRD. The results show that, with the increase of OPC substitution rate, the setting time of UHPC decreases first and then increases, the slump extension continues to increase, and the mechanical performance of UHPC generally shows a decreasing trend in the early stage and an increasing trend in the later stage. The super-early-strength and prolonged initial setting time are mainly due to the cumulative effect of the synergistic hydration and early strength agents, enhancing agents, and slow-setting agents.

The reinforced concrete beam with negative Poisson ratio effect was designed and fabricated by changing the square stirrup of reinforced concrete into six-ribbed structure and star-shaped structure. The flexural performance of concrete was simulated by three-point bending test and drop hammer impact test, and its deformation behavior and Poisson ratio were analyzed by digital speckle correlation method. The results show that the stirrups of six-ribbed structure and star-shaped structure can improve the flexural capacity of concrete, delay the development of cracks, and improve energy absorption rate and flexural toughness. The flexural capacity and coefficient of flexural toughness of star-shaped reinforced concrete are up to 22.6 kN and 3.86 MPa, respectively. With the change of stirrup structure, the flexural performance of concrete is enhanced, but the Poisson ratio decreases, and the phenomenon of negative Poisson ratio even appears in reinforced concrete with star-shaped stirrup. The minimum Poisson ratio can reach －0.03.

The size effect has an important influence on the mechanical properties and structural design of concrete materials. Currently, the test is still the main way to study the size effect of concrete. Limited by the sample preparation period, complex boundary, and loading conditions, the comprehensive cost is high, and the result is discrete. With the help of deep learning and the Bayesian optimization algorithm, based on a large number of test data, this paper established a deep neural network model (BO-DNN) of concrete compressive strength size effect without any simplified calculation assumptions. The model was compared with the existing size effect model, and the influence of each parameter on the size effect of compressive strength was investigated by changing the value of selected characteristic parameters. The results show that the size effect of the water-binder ratio on compressive strength is significant, and the smaller the water-binder ratio is, the more obvious the size effect is. The size effect of compressive strength increases with the increase of the aggregate size, but the increase slows down with the increase of the aggregate size. The size effect of compressive strength of specimens with an aspect ratio less than 2 increases with the increase of the aspect ratio, and the size effect tends to be stable after exceeding 2. The shape of the specimen has little influence on the size effect of compressive strength. The longer the curing age is, the more significant the size effect is, but the size effect tends to be stable after the curing age exceeds 90 d. The prediction model proposed in this paper has strong generalization ability, higher accuracy, and stability, and can better mine the complex nonlinear relationship between the characteristic parameters, providing a theoretical basis and reference for the engineering design of concrete materials and structures.

Three-point bending tests were carried out on concrete notched beam specimens with seven kinds of 3D hooked-end steel fiber content. The influence of different 3D hooked-end steel fiber content on the flexural performance of concrete notched beam specimens was studied with digital image correlation (DIC) technology. According to the test result, it shows that concrete notched beam specimens with 3D hooked-end steel fiber have excellent bending toughness. The load-crack mouth opening displacement (CMOD) curve of concrete notched beam specimens with 3D hooked-end steel fiber has two peak values. Except that the ratio of the second peak to the first peak of concrete notched beam specimen with 3D hooked-end steel fiber content of 25 kg/m3 is 0.91, the other concrete notched beam specimens with 3D hooked-end steel fiber are greater than 1. Based on the analysis, the CMOD-deflection relationship and dissipation energy of concrete notched beam specimens with different 3D hooked-end steel fiber content were obtained. According to the analysis results of DIC data, the applicability of the plane section assumption in the bending analysis of concrete notched beam specimens with different 3D hooked-end steel fiber content is verified, and the change rule of neutral axis position during bending is obtained. Based on the pullout process of 3D hooked-end steel fiber, the tensile and bending failure mechanism of 3D hooked-end steel fiber reinforced concrete were analyzed.

Chloride (Cl-) corrosion is the main problem affecting the service life of reinforced concrete. Because Portland cement and aluminium-rich material (fly ash, slag, etc.) composite systems effectively bind Cl- and improve the corrosion resistance of reinforced concrete, they have attracted considerable research attention. However, the horizontal comparison of Cl- binding capacity of different Portland cement and aluminium-rich material composite systems in existing research is insufficient. First, the process of physical adsorption and chemical binding of chloride in the cement-based system was introduced. Then, Cl- binding capacity of Portland cement and aluminium-rich material composite systems was summarised, and the Cl- binding capacity of composite systems in previous publications was compared with Al2O3 content as the main variable. In addition, various factors affecting the Cl- binding capacity of composite systems were described and analysed. Finally, a more accurate scheme for measuring and comparing the Cl- binding capacity of various Portland cement and aluminium-rich material composite systems for subsequent research was provided, and a theoretical basis for the design of novel high-performance Portland cement and aluminium-rich material composite systems was provided.

The adsorption process of rare earth elements on the surface of aluminum (hydrogen) oxide minerals has an important impact on the enrichment of rare earth elements in bauxite and the extraction recovery of rare earth elements in the adsorbed state. In this research, boehmite was selected as the model mineral, and La and Y were chosen as the representatives of light and heavy rare earth elements, respectively. The effects of adsorption time, solution pH value and background electrolyte concentration on the adsorption of rare earth ions on boehmite were investigated by batch experiments. The results show that the adsorption of rare earth cations by boehmite approaches equilibrium within 72 h, and the adsorption rates of La3+and Y3+ are about 45% and 35%, respectively. In the selected pH value range, the adsorption rate and the background electrolyte concentration rise with the increase of pH value. Due to the protonation effect, the surface of boehmite possesses positive charges under weakly acidic conditions, and electrostatic repulsion occurs between rare earth cations and the surface. So it can be speculated that inner-sphere complexes may be formed between rare earth elements and the surface of boehmite. Compared with heavy rare earth cations, boehmite is more likely to uptake light rare earth cations. The adsorption behavior of rare earth elements by boehmite is fitted better by Langmuir monolayer adsorption model and the pseudo-second-order kinetic model.

The preparation of calcium carbonate block materials in actual production is extremely difficult, and the manual method of manufacturing calcium carbonate often results in only micrometer-scale powder. Coral powder and vaterite-type calcium carbonate were used as raw materials, and pressing forming was employed to control the transformation of vaterite to needle-like aragonite-type calcium carbonate by utilizing the crystal nucleus effect of coral powder. A three-dimensional spatial structure was formed by interweaving and overlapping the aragonite needle-like structures, resulting in the preparation of well-performing calcium carbonate cement. The effect of coral powder on hardening process and strength of calcium carbonate cement was studied, the phase composition, microstructure and pore structure of hardened calcium carbonate cement were systematically analyzed. The results show that the hardening of calcium carbonate cement is directly related to the transformation process from vaterite to aragonite. When coral powder content is 40% (mass fraction), the mechanical properties of calcium carbonate cement are the best, and the compressive strength of 2 and 6 h reaches 27 and 33 MPa, respectively. The addition of coral powder induces the transformation of vaterite to aragonite, inhibites the transformation of vaterite to thermodynamically most stable calcite, and reduces the most probable pore size and more harmful pores.

The influence on mechanical properties, phase composition, microstructure of cement slurry with granite powder (GP) as a mineral material was conducted by using X-ray diffractometer (XRD), scanning electron microscope (SEM), synchronous thermal analyzer (TG-DSC). The results show that under standard curing condition, the compressive strength of cement slurry containing 15% (mass fraction, the same below) GP curing for 28 d reaches 37.0 MPa, which is highest value. The linear shrinkage of cement slurry with 10% GP curing for 56 d decreases by 18.3% than that of cement slurry without adding GP. The initial setting time and final setting time of cement slurry containing 20% GP are shortened by 207%, 18.2%, respectively. The flexural strength of cement slurry with 20% GP curing in water for 28 d is 48% higher than that under standard curing. GP participates in the hydration process of cement slurry through pozzolanic effect to form more hydrated calcium silicate (C-S-H). Adding GP can promote the formation of type I C-S-H in cement slurry, which is beneficial to improve the mechanical properties and shorten the setting time of cement slurry.

In this paper, the effects of different kinds of sulfate-containing solid wastes on the hydration of Portland cement were studied. The mechanical properties, setting time and linear expansion rate of cement mixed with different kinds of sulfate-containing solid wastes were tested with the change of SO3 content. The influence mechanism of different sulfate-containing solid wastes on the hydration of Portland cement was revealed by means of chemical bound water, XRD and SEM. The results show that with the increase of SO3 content, the flexural strength and compressive strength of cement mortar containing sulfate solid waste increase first and then decrease. The initial setting time and final setting time show an increasing trend, and the increase rate slows down after the SO3 content reaching a certain value. The linear expansion rate continues to increase. The linear expansion rate of cement mixed with various kinds of sulfate-containing solid wastes shows an increasing trend. Due to the different forms of sulfate in different sulfate-containing solid wastes, the dissolution rate of different types of sulfate is also different. The rate and quantity of ettringite (or monosulfoaluminate hydrated) formed by the reaction with tricalcium aluminate in cement are also different, and the degree of hydration at the same age is also different. Therefore, different sulfate-containing solid wastes have different effects on the mechanical properties, setting time and linear expansion rate of cement.

The geopolymer has the advantages of low carbon and environmental protection, but for low calcium fly ash geopolymer, however, there exists some issues including high viscosity, excessively long setting time at room temperature and low strength. The effects of different factors including liquid/solid ratio, alkaline solution concentration, superplasticizer content and slag content on rheological properties, setting time and compressive strength of low calcium fly ash geopolymer were investigated. The results show that the modified Bingham model fits relatively well with the rheological properties of fresh geopolymer. Yield stress is affected most by slag content, and increases with the increase of slag content. Plastic viscosity is affected most by liquid/solid ratio, and decreases significantly with the increase of liquid/solid ratio. The setting process is rather slow for pure low calcium fly ash geopolymer at room temperature, and the initial setting time is over 8 h and the final setting time is over 23 h. When liquid/solid ratio is 0.40, alkaline solution concentration is 29% (mass fraction) and slag content is 25% (mass fraction), the corresponding initial and final setting time are 54 and 145 min, respectively, and the 7 d compressive strength is 23.2 MPa. Adding 0.3%~0.5% (mass fraction) polycarbonate superplasticizer, the 28 d compressive strength of pure fly ash geopolymer increases by around 20%。

Due to the low early hydration activity, poor grindability and soundness of steel slag, which restricts its large-scale utilization in cement and concrete. In this paper, the mineral phase transformation and the changes of grindability, soundness and activity index of reconstructed steel slag at different reconstructed temperatures were studied. The results show that the high temperature optimizes the mineral phase composition of steel slag, promotes the transformation of the refractory phase (FexO) and RO phase, promotes the transformation of dicalcium silicate (C2S) to tricalcium silicate (C3S) in steel slag, and promotes the formation of magnesium iron spinel (MgFe2O4). The reconstructed steel slag with uniform mineral and liquid phase distribution, good mineral composition and clearer boundary often shows higher strength, and the 28 d activity indexes of the two kinds of steel slag at the 1 400 ℃ reach 99.03% and 96.52%, respectively. The f-CaO content in steel slag decreases significantly with the increase of reconstructed temperature, and the grindability increases first and then decreases with the increase of reconstructed temperature.

The purpose of using copper slag tailings as filler on the performance of asphalt mixture, the physical and chemical properties of copper slag tailings were analyzed, the optimum mix ratio of asphalt mixture was determined through Marshall stability test. Rutting test, split test, freeze-thaw split test, and immersion Marshall test were carried out to evaluate the road performance of asphalt mixture, and the copper slag tailings asphalt pavement was tested. The adhesion characteristics of copper slag tailings and asphalt were analyzed by microscopic morphology. The results show that the content of copper slag tailings in AC-25C, AC-20C, AC-16C and AC-13C asphalt mixture is 4%, 3%, 3% and 2% (mass fraction) respectively, and the asphalt mixture has the best performance when the corresponding asphalt content is 38%, 42%, 45% and 46% (mass fraction). Compared with limestone asphalt mixture, the high-temperature stability, crack resistance and water stability of copper slag tailings asphalt mixture have been significantly improved. Copper slag tailings asphalt pavement has good performance. Its water permeability coefficient is 62 mL/min, friction coefficient is 90, and compactness is 96.4%, all of which meet the specifications and standards. The asphalt mortar formed by copper slag tailings and asphalt has good bonding performance.

Phosphate cementitious materials have good mechanical properties, and simple preparation process, which provide a new way for resource utilization of copper slag. Phosphate cementitious materials were prepared using copper slag and sodium dihydrogen phosphate (NaH2PO4) as raw materials. And the effects of raw material mix ratio and curing conditions on compressive strength, phase and microstructure of copper slag-based phosphate cementitious materials were studied by universal testing machine, X-ray powder diffractometer and scanning electron microscope. Besides, the thermal stability of copper slag-based phosphate cementitious materials was also investigated by simultaneous thermal analyzer. The results show that raw material mix ratio has an important influence on mechanical properties and microstructure of phosphate cementitious materials. And appropriately increasing the curing temperature is conducive to strength development. When the mass ratio of NaH2PO4 to copper slag is 0.30, the mass ratio of water to NaH2PO4 and copper slag is 0.15, and the curing temperature is 60 ℃, the 7 d compressive strength of copper slag-based phosphate cementitious materials is as high as 54.70 MPa. The excellent mechanical properties are due to the dense amorphous phase formed by the reaction of fayalite (Fe2SiO4) in copper slag with NaH2PO4. Furthermore, the copper slag-based phosphate cementitious materials have good thermal stability. It begins to be oxidized and decomposed at 467 ℃ under air atmosphere, and the amorphous structure phase undergoes phase transition.

Boron mud, as a waste of the boron industry, has not been effectively utilized and poses great harm to the environment. In this study, boron mud treated by high-temperature calcination was used as raw material to prepare magnesium oxysulfide cement. The effects of different calcination conditions on boron mud and the influences of boron mud calcination temperature, holding time, and content of calcination products on the mechanical properties, phase composition, and microstructure of magnesium oxysulfide cement were investigated. The results show that MgCO3 in boron mud can be decomposed to obtain highly active MgO at 700 ℃ after holding for 2 h, and the burning loss rate of boron mud is maintained at 23.50%, while the hydration activity reaches the highest at 24.64%. Magnesium oxysulfide cement prepared with 45% boron mud content under calcination conditions of 700 ℃ and holding for 2 h has the best mechanical properties. The bulk density is 1.7 g/cm3, the 28 d compressive and flexural strengths are 59.0, 8.0 MPa.

Alkali-activated steel slag-slag pervious concrete (ASSPC) was prepared by using steel slag-slag composite powder instead of Portland cement and steel slag aggregate instead of natural aggregate. The compressive strength of ASSPC under different factors was studied, and the microscopic properties of hardened cementitious materials and interfacial transition zone (ITZ) of ASSPC were characterized by XRD, TG, FESEM and SEM-EDS. The effects of cementitious materials on the development of mechanical properties of ASSPC and its influence mechanism were clarified. The results show that ASSPC has high early compressive strength. With the increase of steel slag-slag ratio, the compressive strength increases first and then decreases. Using steel slag as aggregate to prepare pervious concrete effectively optimizes the microscopic properties of ITZ and improves the mechanical properties of ASSPC. With the increase of water-binder ratio (0.24～0.32), the compressive strength of ASSPC increases first and then decreases.

Due to alkali-activated slag-red mud cementitious material (AASR) with high water absorption rate, water and erosive ions are easily enter into AASR interior, which poses a great threat to AASR durability. Sodium stearate (NaSt) was used to improve the pore structure of AASR, and a water-repellent film was introduced on the pore wall, which reduces its water absorption rate of AASR. The improvement mechanism of NaSt on the water absorption rate of AASR was revealed by analysing of the pore structure, contact angle and micromorphology of AASR. The results shows that NaSt introduces more closed pores into AASR interior and the connectivity of the internal pores will be blocked by these closed pores, thus the water transport is blocked in the AASR pore size. A water-repellent film formed by NaSt is formed in the capillary wall, which increases the contact angle of the pore wall and reduces the capillary suction. The reduction of initial water absorption rate of AASR with adding 0.5% (mass fraction) NaSt is up to 83%, but it has less effect on mechanical properties.

Different types of fibers and tailing sand were adopted to prepare the environmentally friendly mixed fiber-tailing sand engineered cementitious composites (MFT-ECC). Fluidity and mechanical properties were taken as the indicators, and the optimal content of different fibers in MFT-ECC was selected through orthogonal tests. The four-point bending fatigue test was applied to compare the fatigue properties of each ECC specimen under different stress levels. The microstructure of MFT-ECC was observed with scanning electron microscope. The results show that the fluidity and mechanical properties of MFT-ECC are optimal when the volume fraction of polyvinyl alcohol fiber, calcium carbonate whisker and modified polypropylene fiber is 0.9%, 0.8% and 0.3% respectively. The MFT-ECC with optimized content has the best fatigue performance, the fatigue life has low sensitivity to stress changes, and its strength reduction coefficients compared with the base group under different stress levels increase by 1.33% and 6.56%. The adding of tailing sand in the ECC leads to the filling effect and stacking effect, which improves the compactness of material. This study provides a reference for the preparation of low-cost and environmentally friendly ECC materials with excellent performance.

Developing of high-grade cementitious materials with lower clinker content is one of the most effective ways for the peak carbon dioxide emissions in cement industry, which proposes a higher requirement for the utilization of admixtures and the synergistic effect of different admixtures. In this study, clinker-silicomanganese slag-limestone compound cementitious materials were prepared by using local industrial solid waste silicomanganese slag and a rich resource of limestone in Sichuan province. Properties and hydration characteristics of compound cementitious materials were studied. The results show that the clinker-silicomanganese slag-limestone compound cementitious materials have proper workability and significantly improved later-stage mechanical properties. The problems of prolonged setting time and early strength too low in compound cementitious materials with silicomanganese slag used alone can be effectively improved by the addition of limestone powder. The early nucleation-hydration induction effect of limestone powder and the late hydration activity of silicomanganese slag are fully developed in the clinker-silicomanganese slag-limestone compound cementitious materials system. In addition, synergistical hydration effect of silicomanganese slag and limestone powder can consume aluminum phase to generate the carbonaluminate hydrates, increasing the hydration products and preventing the transformation from AFt to AFm, which is conducive to the stable improvement of the mechanical properties.

The solubility and dissolution rate of gypsum have important effects on the hydration and properties of anhydrous calcium sulfoaluminate. In this paper, isothermal calorimeter, XRD, TG-DTG and other test methods were used to study the dissolution characteristics of hemihydrate gypsum, dihydrate gypsum and anhydrite and their effects on the hydration process of anhydrous calcium sulfoaluminate. Based on Krstulovic-Dabic and Kondo model, the kinetic parameters of each stage of hydration reaction were calculated. The results show that the solubility of hemihydrate gypsum, dihydrate gypsum and anhydrite in pure water is 2.74, 2.30, 2.38 g/L, respectively. The dissolution rate of hemihydrate gypsum is the maximum, followed by dihydrate gypsum, and the minimum is anhydrite (1 h solubility is 1.19 g/L). The addition of gypsum shortens the induction period of hydration of anhydrous calcium sulfoaluminate and accelerates the process of hydration, where hemihydrate behaves most significantly, with the hydration heat curve having almost no induction period, followed by dihydrate, and anhydrite having the least effect on the induction period. At the beginning of the acceleration period, the hydration rate constant from small to large is anhydrite system, dihydrate system, hemihydrate system. The dissolution rate and solubility of gypsum affect the formation process of ettringite. The gypsum with large dissolution rate prompts the appearance of ettringite precipitation at the early stage of hydration and the amount reaches the maximum value quickly. And in the same time, the system with the addition of gypsum with high solubility has a large amount of ettringite production. At 1 h of hydration, the amount of ettringite produced in the hemihydrate system is about 15.77% (mass fraction) of the total sample, 13.28% (mass fraction) in the dihydrate system and only 3.60% (mass fraction) in the anhydrite system.

To further improve the rationality of design and management of low alkali recycled aggregate planting concrete in various scenarios of sponge cities, the pore size distribution of natural aggregate, recycled concrete aggregate and recycled red brick aggregate were first measured by mercury intrusion porosimetry, then the water absorption rate-time curves and water content-time curves of planting concrete with different aggregates were measured separately in both water absorption and water reversion states. Characterization model of water absorption and reversion characteristic of low alkali recycled aggregate planting concrete established and Pearson correlation coefficients were applied to reveal the microscopic mechanism of water absorption and reversion characteristics of planting concrete. The results show that the water absorption rate-time curves (goodness of fit R2 no less than 0.95) and water content-time curves (goodness of fit R2 no less than 099) are fitted accurately by power function and double exponential function. The water absorption model includes two parameters, which are initial water absorption coefficient and incremental water absorption coefficient. The water reversion model includes three parameters, which are initial water content coefficient, initial water reversion coefficient and residual water content coefficient. Aggregate type significantly affects the water absorption and reversion characteristic of low alkali planting concrete, and this difference mainly comes from the pore structure of aggregate. A higher porosity of pores above 100 nm in aggregate provides planting concrete with a higher initial water absorption rate, stronger sustained water absorption capacity, a higher saturated water absorption rate, but reduce the residual water absorption rate after water reversion. Pores lower than 100 nm of aggregate increase the residual water content of planting concrete. In addition, the pores below 100 nm continuously absorb water through capillary action, and some pore structures have small pores (below 100 nm) in series with large pores (above 100 nm), forming a siphon structure with capillary pores absorbing water and large pores storing water, thus the continuous water absorption capacity of planting concrete is significantly related to both the pores above 100 nm and below 100 nm.

In order to investigate the effect of naphthalene sulfonate water reducer (FDN-C) used in concrete on soil solidification, different amounts of FDN-C were added into high plastic clay, compared with calcium lignosulfonate (CA-LS), the compaction load, unconfined compressive strength (UCS) were tested. The mechanism was analyzed by testing the particle size, microstructure, bonded water, mineral composition and functional group of solidification treated samples. The results show that, like CA-LS, FDN-C can also reduce the compaction load and improve the UCS. When the dosage is higher than 0.7% of soil sample mass, the UCS has little difference, while the compaction load of samples added FDN-C is lower. FDN-C and CA-LS improve the UCS by dispersing soil particles, reducing the thickness of bonded water on the surface of soil particles, and reducing the particle spacing, so that the soil particles can be better filled and compacted with each other, thus improving the engineering properties of soil. CA-LS has a strong ability to reduce the thickness of weak bonded water, while FDN-C reduces the thickness of strong bonded water. More free vacancies in CA-LS molecules make it have certain adhesion, which can make soil particles better cemented together, but the similar effect is not found with FDN-C.

In view of the interception problem of organic pollutants and inorganic metal ions combined with groundwater pollution sources, a design method of geopolymer interception wall material with cetyltrimethylammonium bromide (CTAB) as modifier was proposed, and the influence of the amount of modifier on the permeability coefficient, compatibility, adsorption capacity and compressive strength of geopolymer were studied. The results show that the modified geopolymer has a high adsorption capacity to the phenol-hexavalent chromium compound groundwater pollution source under the premise of maintaining good permeability coefficient, compatibility and compressive strength, and can be used as an economical and effective interception wall material. When the content of sodium silicate is 8%(mass fraction), the modulus of sodium silicate is 1.0, the water-raw material ratio is 0.30, and CTAB addition is 2.0%(mass fraction), the permeability coefficient of the sample is 4.61×10-8 cm/s, the compressive strength is 6.25 MPa, and the removal rates of phenol and Cr (VI) can reach 57.51% and 28.18%, respectively. In addition, with the increase of CTAB addition, the permeability coefficient and adsorption capacity of the modified geopolymer increase, while the compressive strength decreases, and no deterioration phenomenon appears in the test blocks.

During the operation of a proton exchange membrane fuel cell (PEMFC), free radicals generated by PEMFC usually attack proton exchange membrane (PEM), causing the formation of crack or holes, which make the cell failure. Adding free radical scavenger material into PEM is regarded as a commonly modification method. Here, a Sn-doped CeO2 free radical scavenger was synthesized. By increasing the concentration of Ce3+, the free radical scavenging performance of CeO2 in PEMFC could be enhanced, which could avoid PEM thickness to decrease rapidly, and the durability of PEMFC could be improved. Density functional theory calculation and experimental results show that Sn-doping can cause lattice distortion of CeO2, reduce the formation energy of oxygen vacancy, and improve the formation of Ce3+ in CeO2. At the same time, the addition of Sn2+ can reduce Ce4+ in CeO2-Sn to form Ce3+, which is conducive to increasing the concentration of Ce3+ and thus improving the durability of PEM. The results of single cell test show that the voltage attenuation rate of the single cell assembled with CeO2-Sn-5% modified is the lowest (18%) and the power retention rate (56%) of the single cell is higher than that of other PEM after 70 h open circuit voltage decay test, which indicates that the sample has better durability.

Silicon nitride ceramic pipes were prepared by extrusion with carboxymethyl cellulose (CMC) as the binder. The effect of binder content on the performance of green ceramic pipes was studied. The effect of sintering temperature on the relative density, flexural strength and microstructure of silicon nitride ceramics was studied. At the same time, the high temperature strength performance of silicon nitride ceramics was studied. The results show that with the binder content of 7% (mass fraction), the green ceramic pipe can dry and shrink evenly, and the surface is smooth without micro-cracks. At the sintering temperature of 1 740 ℃, the bulk density and flexural strength of silicon nitride ceramics reach the maximum value, which are 96% and (684±23) MPa, respectively. And the flexural strength reaches (380±21) MPa at 1 200 ℃, silicon nitride ceramics show a good high temperature strength performance.

The porous silicon nitride capillary wicks with high porosity, small pore size and narrow pore size distribution were prepared by micropore structure of β-Si3N4 long columnar crystal grains growth and lapping. The effects of sintering temperature, molding pressure and content of pore-forming agent on the pore parameters were studied. The thermal performances of porous capillary wick of loop heat pipe were tested. The results show that the effects of sintering temperature, molding pressure and content of pore-forming agent acting on regulation of the micropore structure have a correlation with the pore size distribution. The diameter of β-Si3N4 columnar crystal grain decreases and the length-diameter ratio increases with the increase of porosity. As a result, the β-Si3N4 columnar crystal grain lapped skeleton tends to be fine and dense, which plays the role of dividing intergranular pores, offsets the increase of pore size caused by the increase of porosity, and realizes the synergy of small pore size and high porosity in a certain range. The regulation of pore parameters of porous silicon nitride is different from those of conventional materials prepared by particle stacking and sintering method, whose pore size increases with the increase of porosity. When the porosity of the typical porous wick materials is 54.0%, the permeability and average porosity of porous silicon nitride are about 6.5×10-14 m2 and 0.3 μm, respectively, more than 95% pore sizes are 0.1～0.4 μm, the maximum capillary force is up to 62 kPa, and the heat load power is over 200 W.

Fly ash and iron tailings were used as main raw materials, and a novel zeolitization ceramsite was successfully prepared by high temperature sintering activation-hydrothermal synthesis process. Basic ceramsite was obtained by high temperature sintering while activating inert phases such as mullite in the raw materials, then the zeolite modification of the basic ceramsite by hydrothermal reaction was carried out to increase the specific surface area and adsorption capacity of ammonia nitrogen. The results show that the optimum preparation conditions are as follows: m(fly ash)∶m(iron tailings)∶m(quartz sand)=7∶1∶2, sintering temperature is 1 040 ℃, sintering time is 30 min, NaOH solution concentration is 15 mol/L, hydrothermal temperature is 160 ℃, hydrothermal time is 12 h. XRD, SEM, FT-IR and Raman tests show that the main crystal phase of the zeolitization ceramsite is zeolite P and analcime. And its specific surface area increases from 1.068 m2/g of the basic ceramsite to 35.770 m2/g, and the maximum adsorption capacity for NH+4-N increases from 1.82 mg/g of the basic ceramsite to 13.34 mg/g, which increase to 33.49 times and 7.33 times of the basic ceramsite, respectively. The present results of this experiment show that zeolitization ceramsite has potential applications in wastewater treatment.

The flat glass industry is a typical industry with high energy consumption and high emission, which cannot be ignored in achieving carbon neutrality goal. Carbon emission of flat glass industry comes from energy consumption and decomposition of carbonates in raw materials, where energy consumption is dominant and accounts for about 80%. Thus, reducing dependence on fossil fuels and enhancing thermal efficiency of glass furnaces are main ways for decarbonization in flat glass industry. The carbon emission from thermal decomposition of carbonate in raw material accounts for around 20%. Optimizing compound formulation and reducing the introduction of carbonate raw material are effective decarbonization strategies. Furthermore, carbon capture can be used to reduce the unavoidable emission of carbon dioxide during the production of flat glass. This paper reviewed the current research status and challenges of decarbonization technology in flat glass industry and explored decarbonization technology suitable for the situation of flat glass industry in China.

The aerospace electrical connectors with electronic glass as sealing material are widely used in aerospace field. Taking the air tightness of electronic glass sealed aerospace electrical connectors as optimization goal, the sealing process of electrical connectors was optimized. Taking the leakage rate of electrical connectors as response objective function, the Box-Behnken design and response surface analysis were used to evaluate the sealing process conditions. The quadratic polynomial regression equation model was established, and the regression equation was analyzed by variance and systematically test. The process parameters such as sealing temperature, sealing time and nitrogen flow were optimized. The results show that the optimal sealing process conditions are heating rate of 10 ℃/min, sealing temperature of 944 ℃, sealing time of 32 min, nitrogen flow rate of 1 408 L/h, and cooling rate of 10 ℃/min. The average leakage rate of aerospace electrical connectors under these conditions is 4.07×10-10 Pa·m3·s-1, which is consistent with the predicted value of regression model. The mechanism of glass and metal sealing is chemical bonding and physical meshing between glass and metal, and the good wetting between glass and metal oxide.