Chloride ion transport is the critical factor affecting the service life of reinforced concrete under marine environment. The chloride ion under marine atmospheric environment causes severely reinforcement corrosion, leading to the reduction of load-bearing capacity and degradation of durability for concrete structures, and posing a severely threat to service life of reinforced concrete structures under marine environment. However, the transport mechanism of chloride ion in concrete under salt spray environment is extremely complex, showing a multi-factor characteristic. Therefore, the more precise salt spray test is need to study, and the targeted model should be established to characterize the transport behavior of chloride ion in concrete. In this paper, the research progress of chloride ion transport in concrete under salt spray environment was systematically reviewed. The test methods of chloride ion erosion in concrete under salt spray environment were summarized, and the influence factors of chloride ion transport were disscussed. The chloride ion transport models were concluded. The paper can provide references for engineering practice and scientific research of reinforced concrete structure under marine atmospheric environment.

Pretreatment is the key step in carbon curing system, which is very important for cement paste carbonization. In this study, the cement specimens before carbonation were pretreated by ultraviolet (UV) irradiation and compared with standard pretreatment, and the carbonation depth, compressive strength, CO2 absorption and structural morphological changes of hydration products were tested and analyzed. The results show that the mass loss of cement specimens after UV pretreatment is 5.3 times as standard curing pretreatment. After accelerated carbonization, the carbonization depth increases by 2.4 times, the mass increases by 4.5 times, the early compressive strength increases by 18.9%, and the CO2 absorption increases by 0.25%. It is found that UV pretreatment increases the formation of silica gel (Q3+Q4) content with high degree of polymerization of carbonized cement specimens. Therefore, UV pretreatment can significantly accelerate the water loss and decalcification of the specimen, which has a significant enhancement effect on the carbonization process of cement specimens.

Under the premise of ensuring the controllable setting time, improving the early strength of potassium magnesium phosphate cement is the key to its engineering application. In this study, borax and sucrose were used as retarding components to regulate the hydration and hardening process of potassium magnesium phosphate cement. The results show that compared with the single-doped borax and single-doped sucrose groups with the same setting time, the second exothermic peak of potassium magnesium phosphate cement mixed with the two (borax and sucrose account for 1.5% and 6.0% of the mass of MgO, respectively) is significantly delayed, but the heat release rate and total heat release increase. The amount of hydration product MgKPO4·6H2O is more, the 3 h strength increases by 104.1%, and the later strength is equivalent to that of the single-doped borax group.

Calcium aluminate special cement with rapid early-age strength development and high-temperature resistance is frequently utilized for well cementing operations in heavy oil thermal recovery. It is essential for understanding the effect of early-age hydrothermal curing on the structural stability of cement binder to maintain cementing safety and oil recovery effectiveness. The strength development, mineral composition, and microstructure of cement cured at 20, 50 and 80 ℃ were investigated. The results show that the main mineral phases formed in calcium aluminate cement, such as gehlenite, CAH10 and C2AH8, gradually transform into granular hydrogarnet with poor cementation during hydrothermal curing, resulting in loose and porous structure of cement binder, which leads to the decline in compressive strength. The incorporation fly ash and slag can not effectively prevent the crystal transformation and structural damage. The modification of sodium hexametaphosphate maintains the structural stability of mineral phases, and the dissolved Na+ and HPO-4 ions released from hexametaphosphate react with Ca2+ and ［AlO4］5- ions released from cement to generate sodium calcium aluminophosphate hydrate (N-C-A-P-H) gel phase products, which further enhances the density and cementation performance of cement binder.

Superelastic shape memory alloy fiber (SMAF) was added into the polyvinyl alcohol (PVA) fiber reinforced engineered cementitious composites (ECC) to prepare a new SMAF-ECC with good self-centering and energy dissipation performance. The self-centering and energy dissipation performance of SMAF-ECC beams with different SMAF end shapes and diameters were investigated by three-point bending cyclic loading test. The results show that increasing the diameter of SMAF can effectively improve the energy dissipation performance of the specimen, but has little effect on the self-centering performance. The difference of deflection self-recovery rate caused by different fiber diameters in the test is only 5%. The end shape of SMAF has the most significant effect on the self-centering and energy dissipation performance of the specimen, anchoring performance of SMAF with the knotted end is the best. After unloading, the main crack width of the specimen decreases significantly, and the deflection self-recovery rate reaches more than 70%. The test curve has obvious flag-shaped energy dissipation characteristics.

The effects of shape memory alloy (SMA) fiber with different content and different diameter on tensile stress-strain relationship, residual strain, crack width and crack recovery rate of engineered cementitious composites (ECC) were studied by uniaxial cyclic tensile test. The results show that the addition of knotted-shaped SMA fiber improves the ultimate strain and ultimate tensile strength of ECC, and the strain recovery rate of pure ECC without SMA fiber is 12% in the late cycle. The strain recovery rate of SMAF-ECC specimens doped with 1.00% (volume fraction) 0.5 mm SMA fiber is as high as 69%, and the crack recovery rate of SMA fiber with 1.00% (volume fraction) 0.5 mm diameter enhanced ECC is 77%. If the fiber diameter grows in a certain range, the strain and fracture recovery rate can be improved, if the fiber diameter is too small, the recovery rate will decrease. The research results provide a theoretical basis for the popularization and application of the new SMAF-ECC specimens.

In order to investigate the influence of calcium silicate hydrate (CSH) gel-montmorillonite interface energy on unconfined compressive strength of cement-stabilized montmorillonite clay, the energy of the interface area between montmorillonite and CSH was quantitatively calculated by molecular dynamics simulation method. Then, combining with the grey correlation degree analysis and X-ray diffraction (XRD), the correctness and deviation sources of the model were discussed. The results show that the CSH-montmorillonite interface energy consists of van der Waals force, hydrogen bonding energy and electrostatic interaction. There is a good correlation between the CSH-montmorillonite interface energy and unconfined compressive strength of cement-stabilized montmorillonite clay. The interface energy decreases with the increase of water molecules, and decreases first and then increases with the increase of montmorillonite layers. At the CSH-montmorillonite interface, the repulsive force can be maximized or the gravitational force can be minimized by adjusting the water-to-cement ratio and the cement-to-soil ratio to obtain an optimal unconfined compressive strength of the cement-stabilized montmorillonite clay.

In order to study the tensile property of polyvinyl alcohol fiber-reinforced engineered cementitious composite (PVA-ECC) after freezing-thawing cycles, the tensile tests were carried out on PVA-ECC specimens with 0, 25, 50, 75, 100, 125, 150 freezing-thawing cycles. The tensile property of PVA-ECC after different freezing-thawing cycles was comprehensively evaluated by surface characteristic and tensile characteristic parameter. In addition, the vector autoregressive moving average (VARMA) model was used to explore the law of tensile characteristic parameter after freezing-thawing cycles. The results show that after freezing-thawing cycles, the specimens are all damaged to varying degrees, and the damage degree gradually increases with the increase of freezing-thawing cycles. The initial crack strength and tensile strength become smaller with the increase of freezing-thawing cycles, and the tensile strain and strain energy increase first and then decrease with the increase of freezing-thawing cycles. Based on the experimental data, some formulas relating to tensile characteristic parameter are proposed, which further reveal the attenuation law of tensile characteristic parameter after freezing-thawing cycles.

The corrosion of reinforcement caused by chloridion is one of the most important factors affecting the durability of reinforced concrete. Chemical consolidation method is the main method to solve the erosion effect of chloridion on reinforced concrete structures. The stability of calcium carboaluminate under different environments was studied by X-ray diffraction analysis, thermogravimetric analysis, scanning electron microscopy and chemical analysis. The results show that calcium carboaluminate is hexagonal plate and has good thermal stability below 120 ℃. But calcium carboaluminat is very unstable in chloride and sulfate solutions, and the CO2-3 in calcium carboaluminate is easily replaced by Cl- and SO2-4 to form Friedel’s salt and ettringite. Calcium carboaluminate is unstable in acidic environment, and will react with acid chemically. It is stable in alkaline environment with pH≥11.

In order to explore the effects of different siliceous materials on the phase of calcium silicate hydrate synthesized by hydrothermal method, the effects of temperature and silicon-to-calcium ratio on the product were studied. The phase of calcium silicate hydrate was analyzed by X-ray diffraction (XRD), and the reaction efficiency of different siliceous raw materials with Ca(OH)2 was investigated. The results show that the reaction efficiency of different siliceous raw materials with Ca(OH)2 from high to low is diatomite, quartz and perlite. In the diatomite-lime system, the amorphous silicon dioxide Si—O in diatomite is easier to be destroyed, and it has instability, resulting in higher reaction efficiency of diatomite. In the quartz-lime system, with the increase of silicon-to-calcium ratio, CO2 in the air can participate in the reaction to generate tilleyite and scawtite, while tobermorite and xonotlite gradually disappear. The reaction product can be effectively controlled by reasonably adjusting the silicon-to-calcium ratio and hydrothermal temperature. This is of great significance to the selection of different siliceous raw materials, the control of products of calcium silicate hydrate and the application field of calcium silicate hydrate synthesized by hydrothermal method.

Compared with traditional grouting materials, leak-proof and high-strength grouting material has two characteristics of leak-proof and high-strength, but the setting speed is too fast, which seriously affects the construction quality. In order to solve the problems of too fast setting speed and bleeding, the effects of hydroxypropyl methyl cellulose (HPMC) and borax on the setting temperature, setting time, water retention rate and flexural strength and compressive strength of leak-proof and high-strength grouting material were studied. The results show that when the HPMC content is between 0.20%～0.30% (the following content are all mass fraction), increasing of the borax content will increase the maximum setting temperature and shorten the constant temperature period time.The addition of HPMC not only improves the water retention rate of the slurry, but also has a certain retarding effect on the grouting material, and the retarding effect of the grouting material is enhanced when it is used together with borax. With the increase of the borax content, the flexural strength and compressive strength of the grouting concretion body increase first and then decrease. HPMC weakens the influence of borax on strength of the grouting concretion body. However, with the increase of HPMC content, the strength of grouting concretion body gradually decreases. When borax content is 0.07% and HPMC content is 0.25%, the leak-proof and high-strength grouting material obtains better working performance under the condition of ensuring good mechanical properties. At the same time, the initial setting time reaches more than 1 h, and the 3 d strength reaches 36.58 MPa. It is found that increasing of HPMC content leads to the transformation of vanadite (AFt) crystal from columnar to acicular, and the flaky mono-sulfur calcium sulphoaluminate hydrate (AFm) gradually decreases, making the structure loose. When borax content is 0.07% and HPMC content is 0.25%, AFt crystal is columnar and evenly distributed, which makes more overlapping points between them, and the structure more compact.

MgO expansive agent (MEA) is an excellent admixture that can compensate for the shrinkage in bulk concrete. The effect of MEA with different activity levels on the pore structure evolution of ultra-high performance concrete (UHPC) paste from 1 d to 7 d was tested by mercury intrusion porosimetry (MIP), and the pore evolution mechanism was also analyzed with the aid of SEM and EDS. The results show that the highly active MEA with a smaller particle size is more conducive to widening the particle size distribution of UHPC and achieving the closest stacking of matrix. The porosity of UHPC paste increases with different activity of MEA at 1 d, but after 3 d, the porosity of UHPC paste at all curing ages decreases with the incorporation of MEA. The higher active the MEA is, the more significant the reduction is. The highly active MEA is more favorable to refining the pore size distribution of UHPC paste in range of 3～67 nm. The use of porosity and pore structure to evaluate the autogenous shrinkage of UHPC should take the effects of different curing ages into account. The higher the active MEA is, the more Mg(OH)2 crystals are produced, which reduces the porosity and refines the pore size distribution. In addition, the relative content of silica fume increases by internal doping method, which contributes to the seeding effect and pozzolanic effect, reducing the final porosity of UHPC matrix.

The effects of mixing durations (120, 210, 300 s) and superplasticizer addition methods (direct or delayed) on rheological properties, pressure bleeding rates, and lubrication layer characteristics of high-performance concrete (HPC) were investigated. And the effects of mixing procedures on pumping properties of HPC were further evaluated. The results show that the flowability of HPC is enhanced by properly prolonging the mixing duration and the delayed addition of superplasticizer. Besides, it needs a longer mixing time to reach the optimum flowability state for mixtures with a larger paste to aggregate ratio. In a certain range, the increasing mixing duration reduces the pumping pressure loss of HPC, but it increases the pressure bleeding rate of HPC, reduces stability of HPC during pumping and increases potential risk of blockage during pumping. Under different mixing procedures, both the viscosity constant of lubrication layer and the bleeding volume at 140 s are well correlated with the pumping pressure loss of HPC, serving as reliable indicators to evaluate the pumping performance of HPC.

By controlling the content of mud powder, different methylene blue (MB) values were measured. The influence of different MB values on the mechanical properties of manufactured sand concrete was studied, and the relationship between pore structure characteristics and mechanical properties was analyzed. The grey relational entropy was introduced to establish the relationship model between pore structure and pore size category of manufactured sand concrete and compressive strength. The results show that the working performance of manufactured sand concrete gradually deteriorates with the increase of MB value. The compressive strength and splitting tensile strength of manufactured sand concrete increase first and then decrease with the increase of MB value. The maximum value occurs at MB value of 1.10 at 28 d, At this time, the T2 spectrum area, porosity, bound fluid saturation and the proportion of harmful pores above 100 nm of manufactured sand concrete reach the minimum. The free fluid saturation and the proportion of harmful pores below 100 nm increase first and then decrease, reaching the maximum when MB value is 1.10, and then the proportion decreases with the increase of MB value, reaching the minimum when MB value is 2.00. By introducing the grey entropy correlation degree, it is concluded that the saturation of the bound fluid and the harmless hole has the greatest correlation degree with the compressive strength, and on this basis, the GM(1,3) model is established. The average relative errors between the model prediction value and the experimental value at 7 and 28 d are 0.47% and 0.26%, respectively.

This paper includes handmade equipment to conduct bending stress loading experiments on coral concrete members. And the influence of bending stress on corrosion of various reinforcement types of steel bar in coral concrete with various protective layer thicknesses was investigated. ABAQUS finite element analysis software was used to simulate the stress magnitude and stress state of the reinforced coral concrete member model under bending stress. The corrosion of several types of steel reinforcement under bending stress was also compared and examined using the polarisation curves and electrochemical impedance spectrum analysis. The findings indicate that handmade equipment can better simulate the corrosion of reinforcing steel under the coupling effect of bending stress and marine environment, and the corrosion resistance of reinforcing steel decreases with increasing bending stress. The effect of increasing bending stress on reinforcement corrosion is significant within a range of protective layer thickness (0~30 mm), but as protective layer thickness increases to a certain point (50 mm), the effect of increasing bending stress on reinforcement corrosion gradually decreases. The influence of bending stress on reinforcement from strong to weak is HPB400 steel bar, galvanized steel bar, 304 stainless steel bar.

Crack resistance and thermal performance are the critical properties of ceramsite lightweight aggregate concrete used in building wall panels. To study the influences of ceramsite pre-wetting time and basalt fiber volume content on the crack resistance and thermal performance of basalt fiber ceramsite concrete, the axial compressive strength, elastic modulus and thermal conductivity tests of basalt fiber ceramsite concrete were carried out in this paper, and the elastic strength ratio and thermal conductivity were used as indicators to evaluate the crack resistance and thermal performance of basalt fiber ceramsite concrete. The results show that both ceramsite pre-wetting and basalt fiber increase the thermal conductivity of concrete, but its thermal performance still meets the specification requirements of ceramsite concrete for the external walls of public buildings. When the volume content of basalt fiber is 0.2% and the pre-wetting time of ceramsite is 72 h, the thermal conductivity of concrete specimen is 0.100 2 W/(m·K) and the elastic strength ratio is 1 109. While meeting the requirements of thermal performance, the crack resistance of concrete specimen increases the most, the increase rate is 19.5%. Based on the existing conversion formula model of concrete elastic modulus and axial compressive strength, a modified model suitable for basalt fiber ceramsite concrete is proposed, and the correlation coefficient is 0.905 7.

Through designing eco-concrete planting tests and scouring tests containing three slope conditions, four slope gradients, and three rainfall intensities, the planting performance of eco-concrete and its scouring resistance after combining with plants were studied. The planting test results show that at 20 d of planting, the plant height of eco-concrete planting group is up to 22.5 cm, the plant spotting index is 95.37% and the plant coverage is 102.6%. The plant stem and leaf growth conditions of the eco-concrete planting group and plain soil planting group are not significantly different, but the plant root in plain soil planting group is generally longer. At 40 d of planting, the root distribution of the two groups is close in extent. The scouring test results show that soil loss in plain soil slope and eco-concrete cladding slope can produce a surge with the increase of rainfall accumulation under specific conditions, while soil loss from eco-concrete planting slope does not surge under all experimental conditions. The scouring resistance under the same scouring condition is eco-concrete planting slope > eco-concrete cladding slope > plain soil slope.

Iron tailings are the main component of bulk industrial solid waste in China. Iron tailings have large inventory, which will cause environmental pollution risk and secondary resource waste if left untreated. How to efficiently utilize iron tailings as resources is an important guarantee for safe consumption of bulk industrial solid waste. Based on the basic properties and utilization way of iron tailings and the principle of electromagnetic wave absorption, this paper mainly introduced the research of iron tailings and its modified electromagnetic wave absorbing materials, iron tailings in cement-based wave absorbing concrete and geopolymer wave absorbing cementitious materials, focusing on the research progress of the wave absorbing properties and mechanism of iron tailings in cement-based concrete. The feasibility and performance of preparing iron tailings-based geopolymer wave absorbing concrete by geopolymerization reaction were discussed, which provides implications for the application of iron tailings-based geopolymers in multifunctional building materials, provides solution ideas to improve the comprehensive utilization rate of iron tailings solid waste resources, and solves the problems of tailings accumulation and environmental pollution. The purpose of this paper is to summarize the research progress of iron tailings in wave absorbing building materials, and further promotes the development of geopolymer wave absorbing building materials.

To achieve the goal of “double carbon”and promote the resource utilization of bulk solid waste, the method and theory of coordinated preparation of foamed ceramics materials by various solid wastes were developed and explored. Foamed ceramics with high closed porosity were prepared by sintering at high temperature with granite scrap and marble scrap as main raw materials and SiC as foaming agent. The effects of raw material ratio, sintering temperature and foaming agent content on the pore structure and properties of foamed ceramics were investigated. The results show that at high temperature, CaO decomposed from the CaCO3 component in marble scrap is an effective flux that destroys the Si—O bond, reduces viscosity of liquid phase and promotes smooth foaming. Meanwhile, CaO can react with SiO2 to form wollastonite, which improves compressive strength of material. The foamed ceramics have the most favorable uniform pore structure and overall performance when the sintering temperature is 1 130 ℃, the marble scrap mass content is 10% and the SiC mass content is 1.0%, with the closed porosity of 79.16%, the bulk density of 583.42 kg/m3, the compressive strength of 3.86 MPa and the water absorption rate of 0.40%. This study provides a theoretical foundation for the preparation of foamed ceramics by recycling granite scrap and marble scrap.

There are many problems in the construction of ocean islands and reefs, including the shortage of materials, high cost of transportation and materials. Therefore, a new type of seawater sea sand volcanic slag concrete (SSAC) was developed to promote the development of marine construction. Through the notched three-point bending beam test, the influences of different initial notch-to-depth ratio (0.2, 0.3 and 0.4) and concrete mix component types on the fracture mechanical properties of SSAC were analyzed. The variations of fracture parameters, such as double K fracture toughness, fracture energy and softening curve were also obtained. The results indicate that the load-crack mouth opening displacement (P-CMOD) curve of concrete with volcanic slag coarse aggregate is similar to that of ordinary concrete, but the descending section of volcanic slag concrete P-CMOD curve becomes steep due to the effects of coarse aggregates. The fracture toughness of SSAC is smaller than that of ordinary concrete, and it is not affected by the initial notch-to-depth ratio. Under the influence of seawater and sea sand, the fracture toughness and fracture energy of SSAC are 14.30% and 6.77% higher than that of fresh water river sand volcanic slag concrete. Based on experimental data, the analytical expressions of double K fracture toughness and softening considering the influence of concrete mix component are established. The calculation results are in line with the test ones.

Coal gangue and waste glass were used as main raw materials to prepare foamed ceramics. The effects of calcination temperature and content of Na3PO4 on phase structure, apparent porosity, compressive strength and apparent density of foamed ceramics were studied. The results show that, as the calcination temperature increases, the linear expansion rate of foamed ceramics samples gradually increases, while the apparent density gradually decreases. The average pore diameter and apparent porosity of foamed ceramics gradually increase and the compressive strength decreases as the calcination temperature or the Na3PO4 content increases, while the apparent density shows different trends and the crystallite structure of the sample changes very slightly. By optimizing the preparation conditions, it is found that when the content of Na3PO4 is 3% (mass fraction) at the calcination temperature of 1 140 ℃, the prepared foamed ceramics exhibits uniform pore structure with the average pore diameter of 0.92 mm, the compressive strength reaches as high as 4.72 MPa, and the apparent density achieves 0.69 g/cm3. The preparation process of foamed ceramics based on coal gangue is simple and the cost is low, which provides a feasible way for the utilization of coal gangue resources.

In this paper, porous sound absorbing materials were prepared by using coal gangue as the matrix component, sodium dodecyl sulfate (SDS) as the foaming agent, ammonium chloride as the coagulant, and borax as the sintering aid in combination with gel injection method and foaming method. And the effects of factors such as water-solid ratio, gelling agent content and sintering temperature on the viscosity of slurry, the apparent porosity, sound absorption coefficient and flexural strength of porous sound absorbing material were studied. The porous sound absorbing material with 49.54% apparent porosity, 0.953 sound absorption coefficient in the frequency band of 1 600 Hz and 2.67 MPa flexural strength is finally produced. The results show that the water-solid ratio has significant effects on the viscosity of slurry, the apparent porosity, sound absorption coefficient and flexural strength of porous sound absorbing material, the gelling agent content mainly affects the porosity and thus the flexural strength of the material, and the sintering temperature mainly affects the pore size distribution and thus affects the sound absorption coefficient of the material at different frequency bands. The water-solid ratio of 0.35, gelling agent content of 35% (mass fraction) and sintering temperature of 700 ℃ are the best preparation process parameters.

All solid waste coal gasification slag glass-ceramics were prepared by one-step direct sintering with coal gasification coarse slag as the raw material. The effects of sintering temperature and time on crystal phase evolution, mechanical and physical properties and microstructure of all solid waste coal gasification slag glass-ceramics were studied. The results show that the coal gasification slag has strong crystallization tendency, and anorthite is the main crystal phase. As the sintering temperature increases in the range of 800~1 150 ℃, the crystallinity of glass-ceramics increases firstly and then decreases. Flake structure appears in the glass-ceramics and the physical and chemical properties decrease when the sintering temperature is too high. In the range of 1 110~1 120 ℃, the glass-ceramics are fine and densely distributed, and show good physical properties. However, the sintering time has little effect on the properties of samples. When the sintering temperature is 1 120 ℃ and sintering time is 2 h, Vickers hardness of glass-ceramics is 6.92 GPa, flexural strength is 38.29 MPa, compressive strength is 432.72 MPa, bulk density is 2.618 g/cm3, water absorption is 0.21%, and acid and alkali resistance are 3.13% and 0.92%, respectively. Excellent mechanical properties are achieved, however, there is still room for improvement in water absorption and chemical stability.

In order to improve the added value of comprehensive utilization of fly ash, this paper systematically studied the optimum conditions for extracting SiO2 from fly ash using the acid base combination method, and a novel method for the preparation of simplified conventional modified silica was proposed based on the optimal extraction conditions. Results show that fly ash is preactivated at 800 ℃ and successfully converted into silicate gel after continuously reacting for 90 min at the temperature of 80 ℃ and the atmosphere of sulfuric acid (solid-liquid ratio (g/mL) of 1∶8, 3 mol/L), and then the silicate gel is dissolved and purified with the action of NaOH with a mass fraction of 30%, and finally, the solution pH value is adjusted to obtain more than 95.7% of SiO2 extraction and silica with SiO2 content greater than 93% (mass fraction). In addition, the silane coupling agent KH560 is successfully covered on the surface of the silica after bonding with the formed silica through Si—O—Si chemical bonding in this novel method. The modified silica, which possesses a superior nature in dispersibility, hydrophobicity and particle size, is obtained under the modification conditions of modifier dosage ratio of 2 mL/g, 70 ℃ and 60 min. And SiO2 content in the resulting product is still above 95.97% (mass fraction), showing a significant improvement in specific surface area (381.97 m2/g, 2.78 times higher than that of unmodified silica), and the Hunter whiteness (91.43%) is close to the standard white board, which meets the relevant standards of Class A industrial grade silica.

The application of steel slag as supplementary cementitious materials is limited by its poor hydration activity and volume stability, while steel slag shows excellent carbonation activity. In this paper, the carbonation degree of steel slag was controlled by adjusting the CO2 concentration and carbonation time. The effect of carbonation on the microstructure and CO2 uptake of steel slag was analyzed, and the volume stability and hydration activity of carbonated steel slag used as supplementary cementitious materials were evaluated. The results show that the 3, 28 d compressive strength of mortar containing 30% (mass fraction) steel slag reduce by 43.2% and 30.0%, respectively, compared to the mortar without steel slag. And paste specimen collapses due to expansion after autoclaving experiment. The CO2 uptake of steel slag is significantly affected by the concentration of CO2. The CO2 uptake of steel slag arrives at 3.67% after carbonation for 3 min at high concentration (volume fraction is 99.9%) of CO2. The volume stability of steel slag is positively correlated with the degree of carbonation, while over carbonation treatment reduces the hydration activity. The 3 d compressive strength of mortar containing 30% (mass fraction) steel slag carbonated for 3, 10 min increases by 28.3% and 15.8%, respectively.

Carbonation leads to the decrease of alkalinity of concrete, which seriously harms the durability of reinforced concrete structures. In this paper, Na2SiO3, NaOH and Na2CO3 were used as alkali activators, and the influences of the types of alkali activators and Na2O equivalent on the carbonation resistance of single-component alkali-activated nickel slag cement mortar were investigated. The results show that, when the Na2O equivalent is the same, the carbonation resistance of single-component alkali-activated nickel slag cement mortar is the best in the single doping of NaOH samples, and the carbonation resistance is the worst in the single doping of Na2SiO3 samples. Na2CO3 partial substitution for Na2SiO3 can improve the carbonation resistance of cement mortar samples, while the effect of Na2CO3 partial substitution for NaOH on the carbonation resistance of cement mortar specimens is related to the Na2O equivalent. With the increase of Na2O equivalent, the carbonation resistance of single doping of Na2SiO3 and mixed doping of Na2SiO3&Na2CO3(3∶1) samples increases first and then decreases. The carbonation resistance of single doping of NaOH samples increases continuously in the early stage, and increases first and then decreases in the later stage. The carbonation resistance of mixed with NaOH&Na2CO3 (3∶1) samples improves in the early stage, but decreases in the later stage.

Aimed at the problem of low utilization rate of stone chips, stone chips wet shotcrete was prepared. The effects of replacement amount of stone chips (replacement of manufactured sand by stone chips), sand ratio and fly ash content on the workability, chloride penetration resistance, sulfate corrosion resistance and pore structure of wet shotcrete were studied. The results show that the mechanical properties and durability of concrete can be improved by the appropriate replacement amount of stone chips, but the greater the replacement amount of stone chips is, the more obvious the decline in the workability of concrete is. Compared with manufactured sand shotcrete, stone chips wet shotcrete has good mechanical properties. On this basis, the proper sand ratio and fly ash content can further improve the workability and durability of stone chips wet shotcrete. When the sand ratio of shotcrete is 55% and the fly ash content is 20% (mass fraction), the comprehensive performance of stone chips wet shotcrete reaches the best, which has reference significance for the application of stone chips in wet shotcrete.

As the electronic communication industry rapidly advances, microwave dielectric ceramics become a hot topic in recent years. In general, the phosphate microwave dielectric ceramics have many advantages, such as low sintering temperature, low dielectric constant, easily prepared powder material, and no significant chemical reaction with sliver, so they could be taken as the low-temperature co-fired ceramics. In this paper, the author outlined the performance of microwave dielectric ceramics under the common structure models of the orthophosphate (PO4) and pyrophosphate (P2O7) series, and doping and recombination of PO4 ceramics. The prepared sample is the mixture of PO4 and P2O7 when the ratio of A-element and P-element molar ratio is greater than 1 in research. For the doping of PO4 ceramics, the A/B ions may be selected for replacement to improve the dielectric property. For the recombination of PO4 ceramics, the principle of performance improvement is as follows: if the temperature coefficient of original sample is the negative value, the composite TiO2 makes the temperature coefficient close to 0; if the value is positive, the materials with negative temperature coefficients are compounded to neutralize the temperature coefficient. Finally, the author proposed the problems existed in the phosphate microwave dielectric ceramics and looked forward to the prospect.

Oxidation intercalation is one of the mainstream methods to prepare graphene oxide (GO) monolayer/multilayer materials. The key steps are oxidation agent and intercalation agent selection and process matching. The traditional process maily uses Hummers method which has problems such as large amount of nitrogen oxide emissions, significant environmental hazards and poor safety. In this paper, the research progress of graphene oxide prepared by oxidation intercalation in recent years was reviewed. The green oxidantion agent, intercalation agent research progress and corresponding process improvement and innovation were emphatically expounded. The reaction mechanism and application effect of different agents were systematically analyzed, aiming to find a green, low-cost and more suitable preparation method for industrial production.

The effect of graphene on the performance of Fe-based metal binder diamond abrasive tool was studied by adjusting the graphene content in Fe-Co-Cu-Sn. The microstructure, phase structure, mechanical properties and physical properties of Fe-based metal binder diamond abrasive tool were tested by X-ray diffractometer, scanning electron microscope and universal mechanical testing machine. The results show that the graphene content in binder only affects the content of crystalline phase. When the graphene content is 0.4% (mass fraction), the bending strength of abrasive tool is the highest, being 256.0 MPa, which is 17.4% higher than that of abrasive tool without graphene. With the increase of graphene content, graphene changes from flake like uniform distribution to gradual agglomeration, and the fracture structure changes from brittle fracture to ductile fracture. With the increase of graphene content, the thermal expansion coefficient of abrasive tool gradually decreases and the thermal conductivity gradually increases. The abrasive ratio of abrasive tool increases first and then decreases. When the graphene content is 0.4%, the abrasive ratio is the highest, being 199.8, which is about 21% higher than that of abrasive tool without graphene.

The transportation engineering in the western region of China is facing extremely complex engineering geological challenges, while there are fewer researches on high-performance concrete aggregate suitable for the deep ground environment in the western region. High carbon ferrochrome slag was used as the main raw material to prepare spinel-forsterite high-strength ceramic aggregate for the deep ground high temperature environment in the western region. The effects of sintering temperature and holding time on the physical properties, microstructure and crystal relative content of spinel-forsterite high-strength ceramic aggregate were studied. The results show that increasing the sintering temperature and holding time promote the crystal growth and effectively enhance the physical properties of samples. Under the optimal synthetic conditions (sintering temperature 1 500 ℃, holding time 3 h), the spinel-forsterite high-strength ceramic aggregate exhibites a high compressive strength of 281.1 MPa, apparent density of 3 100 kg/m3, and water absorption of 1.4%. In this case, the utilization rate of high carbon ferrochrome slag is 77.6% (mass fraction). After curing at 80 ℃ for 28 d, the microstructure of high-strength ceramic aggregate concrete is more dense than that of high carbon ferrochrome slag concrete and ordinary aggregate concrete. Furthermore, the interfacial transition zone of high-strength ceramic aggregate concrete is significantly improved, and this concrete is suitable for the deep ground high temperature environment.

SiC fiber fabric is an important toughening material for high temperature resistant ceramic matrix composites. In this paper, plain weave SiC fiber fabrics were taken as the research object. The uniaxial tensile test and ±45° off-axis tensile test were carried out to obtain tensile and shear properties. Yarn extraction test was performed to obtain the friction coefficient between the warp direction and weft direction yarns. X-ray computed tomography (CT) scan was carried out to obtain miscrostructure, and the cross-section and crimp shape of the warp direction and weft direction yarns were fitted by the least squares method. The simply beam model of the yarn was established to calculate the friction moment of the yarn under shearing process, and the shear stress-strain curve of plain weave SiC fiber fabrics can be predicted. The shearing process of plain weave SiC fiber fabrics is divided into two stages, the pure shearing stage and the yarn extrusion stage, and the junction point of the two stages can be defined as the locking angle of plain weave SiC fiber fabrics. The results have reference value for the subsequent design and preparation of plain weave SiC fiber fabric preforms.

Polymer steric stabilization is the main mechanism of ceramic suspension stabilization. In this paper, the alumina suspension stabilized by steric mechanism was studied. The influence laws of volume fraction of suspension, content of polymer and particle size on the elastic modulus were studied through rheological property tests. The results indicate that the two rheological testing modes of steady-state shear and oscillatory shear prove that the suspension has obvious elastic characteristics. It is determined that the core factor affecting the elastic modulus of alumina suspension in steric stabilization is the particle surface spacing, due to the particle surface spacing affecting the compression degree of adsorbed polymer. Increasing the volume fraction of suspension and decreasing the particle size both improve the elastic modulus of the system by reducing the particle surface spacing and the thickness of compressed adsorption layer, meanwhile elasticity increases, and the stability of suspension is affected.

Solution supersaturation ratio and crystallization pressure are the main parameters to study the crystallization failure effect of porous materials, but there are no good means to measure solution supersaturation ratio directly at present. Observations on the phenomenon of solution crystallization show that the gray scale of the image changes obviously before and after the solution crystallization, therefore, a method for measuring the supersaturation ratio and crystallization pressure of salt crystallization based on digital image processing (DIP) technology was proposed. Based on the image,the relationship between gray value and solution concentration was obtained. MATLAB software was used to draw the distribution of solution supersaturation ratio and crystallization pressure. Taking the crystallization behavior of Na2SO4 solution and NaCl solution as an example, the initial supersaturation ratios of Na2SO4 solution and NaCl solution are obtained between 1.1~1.3, and the theoretical values of Na2SO4 and NaCl crystallization pressure are calculated. The differences of the crystallization failure effect between Na2SO4 and NaCl are related to their different crystallization behaviors. The creep growth behavior of Na2SO4 crystals makes them more destructive.

The SCI-E papers in the field of lithium iron phosphate (LiFePO4, LFP) battery materials were sorted out and analyzed in this article from bibliometric analysis perspective. Using CiteSpace6 tool, based on SCI-E database, the highlight word time zone map and keyword clustering visualization knowledge map of LFP battery materials were constructed, simultaneously exploring the knowledge evolution and visualization development trend of LFP battery materials. Through LFP battery materials highlight word time zone map, the knowledge evolution path of LFP battery materials extends from preparation method to the performance research in application field, and finally to the recycling of spent LFP battery materials. According to keyword clustering visualization knowledge map, the development trend was obtained. The representative development trends of LFP battery materials involve power battery performance improvement technology, spent battery recycling and battery online thermal runaway management.

In order to change the present situation of horizontal drawing forming of glass tube based on intuitive knowledge and empirical design, a numerical simulation model of heat and mass transfer in horizontal drawing process of glass tube was established by using ANSYS Polyflow software, then the changes of temperature field, velocity field, pressure field, viscosity field and so on were obtained. Through the numerical simulation analysis, it is concluded that the molten glass inflow temperature, pulling speed, blowing air inflow pressure and rotating cylinder rotational speed are all the sensitive technological parameters affecting the glass tube forming. The molten glass inflow temperature and blowing air inflow pressure are directly proportional to the outside diameter of glass tube and inversely proportional to the wall thickness of glass tube. The pulling speed is inversely proportional to both the outer diameter and the wall thickness of glass tube, and the rotating cylinder rotational speed is directly proportional to the eccentricity of the forming position. The numerical simulation model proposed in this paper will provide theoretical support for improving the quality of glass tube, shortening the replacement adjustment time, improving production efficiency, and saving material and energy consumption.

Andalusite is one of the most important raw materials for alumina-silica refractories, exhibiting excellent alkali attack resistance due to its mullite-high silica glass phase structure after complete mullitization. However, the correlation of its mullitization process and alkali attack resistance has not been fully revealed. In this work, the mullitization process and microstructural evolution of andalusite with the size of 3~5 mm after firing at 1 450~1 600 ℃ for 3 h were investigated, and the alkali attack resistance behavior was evaluated according potassium vapor method. The results show that with the increase of calcining temperature, the andalusite on the surface and near the crack area transforms into mullite-high silica glass phase structure firstly, and then the transformation occurres inside gradually until completing mullitization. The alkali attack resistance behavior depends on the degree of mullitization. After calcining at 1 450 ℃, a thin layer of mullite-high silica glass phase composite structure is formed, and the main alkali attack process occurs directly between potassium vapor and andalusite, resulting in poor alkali attack resistance. After calcining at 1 500 ℃ and above, a mullite-high silica glass phase composite layer with a certain thickness is formed on the surface and near the large crack of andalusite. Potassium vapor and high silica glass phase firstly react to form potassium silicate liquid phase, and then the liquid phase produces erosion and dissolution on mullite phase, preventing the direct reaction erosion of alkali vapor on mullite. Thus, andalusite shows excellent alkali attack resistance.

Quartz sand with two kinds of particle sizes was used as raw materials and the lime milk and waste paper pulp were used as binders to prepare silica brick after sintering at 1 430 ℃. The effects of multi-mineralizer and holding time on the phase composition, microstructure and main physical properties of silica brick were studied. The results show that the fired specimen is composed of tridymite, cristobalite, and a small content of residual quartz after sintering at 1 430 ℃ for 10 h. With the addition of iron scale powder-CaO-MnO2-SiC or iron scale powder-CaO-MnO2-TiO2, the typical aggregate-matrix refractory structure in silica brick disappears, as well as the homogenization effect appears. The fired specimen has good comprehensive properties after sintering at 1 430 ℃ for 10 h when the mineralizer is iron scale powder-CaO-MnO2-TiO2, and the bulk density, apparent porosity, and cold crushing strength are (1.93±0.01) g·cm-3, (14.9±0.1)%, and (55.05±0.64) MPa, respectively. Based on the optimal mineralizer composition and firing system, when the holding time is extended to 15 or 20 h, the residual quartz content in the material decreases, and tridymite content increases, which make that the volume expansion effect is enhanced, and the physical properties of the material are damaged.

Periclase-magnesium-aluminate spinel bricks were fabricated by solid-state sintering method using sintered magnesia, fused magnesia-aluminate spinel and magnesium-aluminate spinel hollow spheres with different particle sizes as raw materials. The phase composition of samples was examined by X-ray diffractometer (XRD), the microstructure of samples was characterized by scanning electron microscopy (SEM), and the bulk density and apparent porosity of samples were measured according to the Archimedes principle method. The effects of lightweight magnesia content and sintering temperature on the properties of periclase-magnesium-aluminate spinel bricks were investigated. The results show that with the increase of lightweight magnesia content, the apparent porosity of periclase-magnesium-aluminate spinel bricks increases, and the bulk density has little change, so it has good mechanical properties. When the lightweight magnesia mass fraction is 25%, the maximum flexural strength of periclase-magnesium-aluminate spinel bricks is 9.56 MPa, and the lowest thermal conductivity is 1.92 W·m-1·K-1. The microstructure shows that the aggregate and matrix are well combined and formed microporous channels. Periclase-magnesium-aluminate spinel bricks have good mechanical properties and alkali corrosion resistance because of their unique microporous structure, which further protect samples from alkali corrosion.

Silicon brick is an acid refractory with high load softening temperature and acid slag corrosion resistance, but it has poor alkali corrosion resistance. Therefore, it is of great significance to study the alkali corrosion resistance of different silica bricks for the application of silica refractories. Four kinds of silica bricks (JG-95# silica brick, BG-96A# silica brick, ZES-99# silica brick and DES-99# silica brick) were selected to compare and analyze the influences of the crystal phase composition and crystalline phase transition on the alkali corrosion resistance of four different silica bricks by chemical analysis, microscopic structure analysis, X-ray powder diffraction analysis and apparent porosity density analysis. The results show that the alkali corrosion resistance of ZES-99# silica brick and DES-99# silica brick is better than that of JG-95# silica brick and BG-96A# silica brick. Silica bricks with higher silica content have stronger alkali corrosion resistance, and silica refractories with cristobalite, tridymite and fused quartz as main crystal phases have good alkali corrosion resistance.