As the strength of concrete increases, its ductility decreases, making it more prone to cracking and adversely affecting durability. Therefore, the study of ultra-high strength, ultra-high toughness cement-based composite holds significant importance. This study combined the design principles of ultra-high-strength concrete and strain-hardening cement-based composites, using polyethylene (PE) fibers as reinforcing materials to develop ultra-high strength strain hardening cement-based composite (UHP-SHCC). The mechanical properties of UHP-SHCC were comprehensively evaluated using the analytic hierarchy process-criteria importance through intercriteria correlation (AHP-CRITIC) hybrid weighting method, resulting in an optimized mix design with the following proportions: 25% (mass fraction) silica fume, 20% (mass fraction) mineral powder, a sand binder ratio of 0.1, 2.00% (volume fraction) PE fiber, and a water binder ratio of 0.18. Additionally, corrugated steel fibers and hooked-end steel fibers were combined with PE fibers to explore the synergistic effects of the two types of fibers. The results indicate that the inclusion of steel fibers significantly enhances the initial cracking tensile strength of UHP-SHCC. Furthermore, after the failure of PE fibers, steel fibers effectively provide bridging action, delaying specimen failure, increasing the ultimate tensile strain, and reducing crack width in UHP-SHCC.

Aimed at early disease of cement concrete structure in service, researches on the composition of early-strength repair materials have important practical significance. This paper employed sulfoaluminate cement (SAC), ferrite-aluminate cement (FAC), and ordinary Portland cement (OPC) to prepare the composite standard cements, respectively, and analyzed the effect of OPC on the setting time and strength of the composite cements to optimize the mix ratio of early-strength repair materials. The hydration heat, scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TG-DTG) tests were used to study the hydration behavior, microstructure, phase composition, and thermal characteristics of the hydration products under the optimal max ratio. The results show that the optimal mass mix ratio of SAC to OPC is 3∶2 and the optimal mass mix ratio of FAC to OPC is 4∶1. Under the optimal mix ratio, the addition of OPC shortens the time to the peak value of heat release rate curve of the composite cements and reduces the total heat release. The results of SEM, XRD and TG-DTG analyses all indicate that with the addition of OPC, affected synergistically by Ca(OH)₂(CH) from the silicate hydration product and the gypsum in OPC, aluminum gel (AH₃) from sulfoaluminate cement hydrate product reacts with CH and CS to form ettringite (AFt), and the tetracalcium aluminoferate (C₄AF) in ferrite-aluminate cement reacts with CH and CS to form a calcium ferrite aluminate solid solution (C₃(A,F) 3CS H₃₂), which facilitates the hydration process of the composite cements. The research results provide a reference for further experimental studies on cement-based materials for early-strength repair materials.

A new type of composite material SMAF reinforced ECC (SMAF-ECC) with high ductility and self-recovery performance can be prepared by incorporating superelastic shape memory alloy fiber (SMAF) into high ductility engineered cementitious composites (ECC). Due to the high price of polyvinyl alcohol (PVA) fiber raw materials used in the preparation of ECC, this paper used relatively low-cost polypropylene (PP) fiber to partially replace PVA fiber to prepare PP/PVA hybrid fiber ECC. SMAF was added to prepare PP/PVA hybrid fiber ECC reinforced by SMAF, so as to reduce the cost of composite materials. In order to explore whether the low-cost SMAF-ECC still had good mechanical properties, the tensile properties of SMAF-ECC with different SMAF content and diameter were studied by uniaxial tensile test. The results show that the content and diameter of SMAF have a significant effect on the tensile properties of SMAF-ECC. The SMAF-ECC specimens with a diameter of 0.2 mm and a content of 0.2% (volume fraction) show the optimal tensile properties, with an increase of 16.79% in the initial cracking stress, and an increase in the ultimate tensile stress and strain of 20.85% and 2.87%, respectively, in comparison with the ECC specimens.

In order to investigate the complex dynamic response of strain-hardening cement-based composites (SHCC), a specialized mechanical shear testing apparatus was employed in conjunction with a hydraulic testing machine and a newly designed split-Hopkinson tension bar (SHTB) for testing, with shear span and notch depth as the primary shear parameters. Shear tests were conducted on two sets of specimens with shear span of 2, 5 mm, and three sets of notch depth of 3, 5, 7 mm, to study the quasi-static and impact shear behavior of SHCC. Digital image correlation (DIC) was used to monitor deformation and crack evolution during the testing process. The research results reveal that shear span influences the shear behavior of SHCC. Shear span and notch depth can control the propagation of shear and tensile fractures, and by selecting an appropriate shear shape, dominant shear fracture of specimens can be achieved. Smaller shear span leads to higher shear forces and narrower areas of predominant shear crack propagation, weakening the material performance. Under both quasi-static and impact loading conditions, the 3 mm notch depth specimen exhibits higher self-confinement and higher fracture strength, displaying a mixed failure mode (compression-shear). On the other hand, the 7 mm notch depth specimen consistently demonstrates the most favorable shear fracture mode, characterized by vertical shear cracks, with shear fracture dominated by crack slip. Therefore, 7 mm notch depth specimen in gravity-loaded SHTB test can be used to accurately assess the shear characteristics of complex mineral-based materials. This study provides a theoretical basis for the optimization of cement-based composites performance.

Cement-based materials are widely used in civil engineering because of high strength and easy construction, but the shortcomings of brittleness and poor flexural properties also limit their application under the condition of high bending resistance. In order to improve the flexural strength, epoxy resin emulsion, nano-SiO₂ and polyvinyl alcohal (PVA)-steel hybrid fiber were added into cement-based materials. The flexural properties and microstructure of cement-based repair materials were studied by the effects of epoxy resin emulsion, nano-SiO₂ and PVA-steel hybrid fibers, which were measured by flexural strength test and scanning electron microscopy test, respectively. The results show that the flexural strength of cement-based repair materials increases first and then decreases with the increase of epoxy resin emulsion content from 0% to 12% (mass fraction), and the maximum flexural strength reaches 7.44 MPa. Both nano-SiO₂ and PVA-steel hybrid fiber can increase the flexural strength of cement-based repair materials by more than 45%, and steel fiber has a more significant effect on the flexural strength. The addition of epoxy resin emulsion and nano-SiO₂ can increase the internal structure density of the matrix greatly to improve the flexural strength of cement-based repair materials. In addition, the bond between the fiber and the matrix is improved for the polymer attached to the surface of the incorporated fiber. This study will provide reference for the application of cement-based repair materials under high bending resistance conditions.

To ensure the long-term self-healing capability of microorganisms is crucial for repairing cracked concrete structures through microbially induced calcium carbonate precipitation (MICP) technology. The long-term microbial self-healing capabilities of cracked mortar mixed with Bacillus Pseudofirmus, exposed to water immersion-ambient exposure conditions, were studied by means of comprehensive utilization of crack geometric measurement, as well as XRD, EDS, and SEM analyses. The experimental results reveal that after a 150 d water immersion period, the crack area repair ratio of the samples with initial width below 200 μm is over 80%. The maximum healed crack with a width of 507.8 μm is observed. Furthermore, denser white precipitates are noted on the surface of those 1 500 d samples, but with a limited efficiency in further reducing crack width. However, the white precipitate observed on the newly saw-cut section of a 1 500 d sample provides evidence that Bacillus Pseudofirmus within the mortar has long-term self-healing capability. The results of XRD, EDS, and SEM analyses confirm that the predominant self-healing product within the cracks is microbially induced calcite.

In this paper, the evolution of mechanical properties and capillary water absorption properties of sulfoaluminate cement (SAC) mortar with different water-cement ratios (W/C) with age was investigated. The pore structure of SAC mortar at specific age and dynamic pore structure during the hardening process were characterized based on low field nuclear magnetic resonance (LF-NMR), combined with mercury intrusion method, water absorption data and theoretical model, the value of the surface relaxation rate of SAC mortar was discussed. The results show that after 0.5 d of standard curing, the compressive strength and flexural strength of SAC mortar with W/C of 0.45, 0.50 and 0.55 are 23.5, 20.8, 16.2 and 4.2, 3.9, 3.6 MPa, respectively, which can basically reach more than 60% of those at 28 d age. At the age of 0.5 d, the capillary water absorption coefficients of SAC mortars with different W/C are 0.020~0.042 g·cm^-2·min^-0.5. At age of 3 d, the capillary water absorption coefficients decrease by 18.5%~25.0%. Thereafter, it changed little until age of 28 d. Within 0.5 d after adding water and mixing, the pore structure of SAC mortar evolves rapidly, and the porosity and pore size distribution gradually stabilize during 0.5~3 d age. The representative capillary tube diameters deduced from data such as capillary water absorption coefficients and theoretical models are closely related to the pore diameters of SAC mortar based on LF-NMR T₂ spectra. When the values of the surface relaxation rate in the fast exchange model are in the range of 0.005 5~0.042 0 μm/ms, the two are relatively close.

In tunnel construction under sulfate-rich environment, attention should be paid to the erosion resistance of concrete structures. Based on the tunnel project of Mouyuan Expressway in Yunnan Province, this study used the method of dry-wet cycle sulfate erosion to explore the effects of different mineral admixtures (fly ash, limestone-based micropowder, silicon-based micropowder) on the apparent morphology, mass and compressive strength of concrete. The microstructure and product changes of specimens were analyzed by means of scanning electron microscopy and X-ray diffraction. The results show that limestone-based micropowder and silicon-based micropowder have good filling effect and pozzolanic activity. After curing in water bath at 50 ℃ for 7 d, additional hydrated calcium silicate (C-S-H) gel can be generated, which can reduce the removal of calcium phase, reduce the damage degree of apparent morphology, mass loss and compressive strength loss of specimens. After 75 dry-wet cycles, the mass of pure cement, 10% fly ash, 10% limestone-based micropowder, 10% silicon-based micropowder, 5% fly ash and 5% silicon-based micropowder decrease by 21.7%, 32.2%, 16.9%, 12.1% and 20.1%, respectively. The strength after erosion accounted for 79.3%, 49.9%, 101.5%, 95.4% and 84.5% of the initial value, respectively. When the C-S-H gel wrapped with calcium hydroxide (CH) crystal in the specimen is seriously eroded, the dry-wet cycle conditions make the CH crystal frequently contact with CO₂ in the air and react to generate a large number of calcium carbonate crystals.

Foam concrete is widely used due to its excellent thermal insulation properties, but the large amount of cement used in its production process leads to high carbon emissions. This study investigated the effects of recycled concrete powder (RCP) replacement and carbonation curing technology on the properties of foam concrete. After 28 d of standard curing, compared with unsubstituted specimens, the properties of specimens containing 10% (mass fraction) RCP are similar. When the RCP replacement rate is 30% (mass fraction), the porosity of specimens increases by 10.9%, the compressive strength decreases by 21.3%, and the thermal conductivity decreases by 11.7%. Compared with counterparts with 28 d standard curing, the properties differences are minimal after 3 d of carbonation curing. After 7 d of carbonation curing, the porosity of specimens decreases by 4.6%~13.4%, the compressive strength increases by 9.8%~16.7%, and the thermal conductivity increases by 6.4%~11.3%. All specimens meet the specification requirements for non-load-bearing thermal insulation exterior wall materials, surpassing the properties of foam concrete reported in the existing literature. Additionally, this study characterizes the phase assemblage of foam concrete, highlighting the high carbon fixation rate of this novel foam concrete, about 12.99% measured using 5 mm of the surface layer. In summary, combining RCP replacement and carbonation curing significantly improves foam concrete properties and carbon fixation capacity, which helps to prepare a novel low-carbon foam concrete product.

Compared to normal aggregates, recycled aggregates have lower mechanical properties, higher water absorption and porosity, which result in poorer mechanical properties of recycled aggregate concrete made from recycled aggregates. This article conducted experimental researches on the splitting tensile mechanical properties of steel fiber recycled aggregate concrete by combining steel fiber and consolidate recycled aggregate, combined with digital image correlation technology and electro-hydraulic servo testing machine. Simultaneously, applying microscopic testing techniques, the influence mechanisms of steel fiber content and consolidate recycled aggregate on the tensile properties of steel fiber recycled aggregate concrete were revealed from the perspectives of interface morphology and interface scale. The results indicate that when the content of steel fiber is high, the influence of aggregate type on the failure mode of concrete is no longer significant. The splitting tensile failure mode of concrete containing steel fiber shows multiple cracks and toughness characteristics. The tensile strength of consolidate recycled aggregate concrete increases by 2.56% to 3.50% compared to normal concrete. The tensile strength of consolidate recycled aggregate concrete is most significantly affected by the steel fiber content, with a maximum increase of 40.50%. The crack resistance of both consolidate recycled aggregate concrete and recycled aggregate concrete are more significantly affected by the content of steel fiber than that of normal concrete. The research results can provide important theoretical basis for the strengthening research and engineering application of recycled aggregate concrete.

Anhydrite is one of the important admixtures to improve the mechanical properties of steam-cured concrete. In this paper, the effect of anhydrite content on the compressive strength, hydration products, porosity, microstructure and durability of steam-cured concrete was studied by mechanical properties, X-ray diffraction, thermogravimetric analysis, mercury intrusion test, scanning electron microscopy, chloride ion penetration and freeze-thaw cycles tests. The results show that anhydrite improves the linear expansion rate of steam-cured concrete. When the content of anhydrite increases from 0% (mass fraction) to 25%, the linear expansion rate increases from 0.03% to 0.25% after steam-curing for 6 h. When the anhydrite content is 15%, compared with the blank sample, the 3 and 28 d compressive strength of steam-cured concrete are increased by 14.4% and 10.5%, respectively. The incorporation of anhydrite helps to increase the amount of ettringite and hydrated calcium silicate (C-S-H), refine the pore, reduce the number of harmful pores, densify the internal structure of steam-cured concrete, and improve its chloride ion penetration resistance. With the increase of anhydrite content, the amount of ettringite in system increases significantly, and the risk of later cracking increases. When the content of anhydrite is higher than 15%, the frost resistance of steam-cured concrete decreases obviously. The content of anhydrite should be controlled at 5%~10%, at this time steam-cured concrete has better mechanical properties and durability.

To address the significant deviation in using wet-sieved two-graded concrete to represent the chloride ion diffusion coefficient of three-graded concrete in ship lock engineering, chloride ion diffusion models for both wet-sieved two-graded concrete and three-graded concrete were established. On this basis, the effects of interfacial transition zone (ITZ) thickness and coarse aggregate volume fraction on the chloride ion transport behavior in three-graded concrete were explored. Additionally, a comparative analysis was conducted on the differences in chloride ion diffusion behavior and durability life prediction between wet-sieved two-graded concrete and three-graded concrete. Simulation results indicate that the chloride ion diffusion coefficient of three-graded concrete decreases significantly with increasing coarse aggregate volume fraction and ITZ thickness. Among the aggregate dilution effect, aggregate tortuosity effect, and ITZ effect, the ITZ effect plays a dominant role. Furthermore, the chloride ion diffusion coefficient of wet-sieved two-graded concrete during 720, 1 800 d of corrosion is 1.77, 1.86 times that of three-graded concrete. And using wet-sieved two-graded concrete to represent three-graded concrete for life prediction may lead to underestimated evaluation results.

In order to explore the effects of temperature and fiber type on uniaxial compression performance of concrete after high temperature, uniaxial compression tests were carried out on normal concrete, polypropylene imitation steel fiber and polypropylene imitation steel fiber-steel fiber reinforced concrete blocks at different temperatures (20, 200, 400 and 600 ℃), and the acoustic emission monitoring system was used to monitor the compression failure process of concrete. According to the test data obtained from acoustic emission and uniaxial compression test, the damage behavior of concrete after high temperature was analyzed. The results show that the compression failure process of concrete is divided into compaction stage, crack propagation stage and instability cracking stage, and the corresponding acoustic emission process is divided into contact stage, slow increase stage and sharp increase stage. The compressive strength loss rate of each sample at different temperatures ranges from 9% to 49%. Through quantitative analysis of acoustic emission signals, it is known that the incorporation of polypropylene imitation steel fiber and polypropylene imitation steel fiber-steel fiber can reduce the initial damage of concrete at 200, 400 and 600 ℃.

To investigate the impact of load bearing strip width on the splitting tensile strength of rock-filled concrete (RFC), a discrete element model of RFC cube with a side length of 600 mm was established. In combination with the existing relevant achievements of splitting tensile strength tests on ordinary concrete and RFC cube specimens, the reasonable value of load bearing strip width in the splitting tensile strength test for large-sized RFC cube specimens was explored. The results indicate that when the load bearing strip width is less than 15 mm (relative load bearing strip width is 0.025), local shear failure occurs near the load bearing strip for the RFC cube specimens. When the relative load bearing strip width is 0.033, the influence of the load bearing strip width on the splitting tensile strength of ordinary concrete and RFC cube specimens of different sizes is relatively close. When the relative load bearing strip width is greater than 0.042, the skeletal effect of rockfill in the RFC cube specimens hinders the crack propagation, resulting in a significant increase in the influence width of the load bearing strip on the splitting tensile strength of the RFC cube specimens. It is recommended that the relative load bearing strip width for the splitting tensile strength test of large-sized RFC cube specimens be taken as 0.033.

Aluminosilicate solid waste (ASW) is discharged in large quantities in industrial production, with SiO₂ and Al₂O₃ as the main components. ASW has a wide range of sources, is cheap and easy to obtain, and contains a large number of high value-added elements, which can be used for element extraction and high-quality material preparation. However, the structure characteristics of amorphous phase and coexistence of multiple crystals lead to low ASW reactivity. Therefore, improving the reactivity is a key prerequisite for the realization of ASW resource utilization. In this paper, the activation methods and mechanisms of typical ASW at home and abroad are analyzed and summarized. The relationship between the structural characteristics and reactivity of typical ASW is analyzed from the amorphous phase and crystal phase structure. The activation methods require for typical ASW with different mineral phase characteristics are clarified. The influence mechanism of different activation methods on the reactivity of ASW is summarized. The typical synergistic activation methods and application fields of ASW are introduced. The future development of ASW activation and utilization is prospected, which provides a reference for the efficient activation and resource recycling of ASW.

Phosphogypsum cementitious materials are formed by mixing phosphogypsum, auxiliary cementitious materials, admixtures and other raw materials according to a certain proportion to form a hardened body with a certain mechanical strength, which has a broad application prospect in the fields of construction, road, environmental treatment and so on. In this paper, based on the existing research results on the preparation of cementitious materials from phosphogypsum at home and abroad, the reaction mechanism and application progress of phosphogypsum cementitious materials are summarized, and the factors affecting the mechanical properties of phosphogypsum cementitious materials are summarized, including the type of phosphogypsum, impurities, dosage, particle size, auxiliary dopants and admixtures, etc. At last, an outlook is given to the development direction of the phosphogypsum cementitious materials, and it is proposed that the future development of composite and functional materials should be developed in the same time as exploring the new type of highly efficient impurity removal processes, and synergizing with other solid wastes to reduce the risk of material leaching toxicity.

In order to achieve high-value utilization of kaolinite type coal gangue in North China, the circular economy of mining area is developed. This paper reported anorthite glass-ceramics was successfully prepared using the kaolinite type coal gangue from Xiegou colliery of Shanxi Province by the sintering process. The effect of different TiO₂ content on the crystallization behavior and the performance of the final prepared glass-ceramics was studied by the methods of X-ray photoelectron spectroscopy, X-ray diffraction, differential scanning calorimetry, physical properties test, etc. The results show that the crystallization temperature of anorthite glass-ceramics decreases from 979.3 ℃ to 915.8 ℃ with the mass fraction TiO₂ increase from 1.09% to 7.09%, and the main crystalline phase can always keep with anorthite, suggesting the TiO₂ content increase reduces the crystallization temperature without change the main crystalline phase. The appropriate addition of TiO₂ can promote the generation of crystal nuclei and increase the number of grains significantly, and the single crystal particles become fine, thus increasing the compactness of glass-ceramics and improving its physical and chemical properties. The glass-ceramics obtained after nucleation at 800 ℃ for 2 h and crystallization at 1 025 ℃ for 2 h with TiO₂ content of 5.09% have excellent physical and chemical properties, with bulk density of 2.88 g·cm^-3, acid resistance of 97.93%, alkali resistance of 99.98%, and flexural strength of 124.5 MPa. The prepared glass-ceramics have excellent performance and good application prospect.

When spontaneous combustion coal gangue is utilized as an aggregate in concrete, its physical properties are often inferior to those of natural gravel. To enhance its resource utilization in building materials, it can be reinforced with cement slurries. The effects of slurry wrapping reinforcement (water-cement ratio is 0.5~1.0) and composite reinforcement (water glass soaking, silica fume doping, pressure soaking) on the apparent density, water absorption, crushing value, needle-shaped flake content and particle size distribution of spontaneous combustion coal gangue aggregate were investigated. The changes in compressive strength and splitting tensile strength of concrete cube with each strengthening method were analyzed. Changes in shape parameters such as axlelength ratio, roundness, and perimeter angularity coefficient after aggregate strengthening and their influence on concrete strength were summarized. Fractal geometry was introduced to verify the enhancement effect of aggregate shape on concrete strength through the fractal dimension of cracks at the time of specimen destruction. The test results show that: when the water-cement ratio is 0.7, the performance of the aggregate strengthened by coating is the best, and the 28 d compressive strength of concrete increases by 11.08%. The aggregate can be further strengthened by three methods (water glass immersion, silica fume doping, and pressure immersion) in composite slurry strengthening, and the 28 d compressive strength of concrete increases by 25.76%, 22.44% and 25.21%, respectively. The shape parameters of aggregate and the fractal dimension of cracks when concrete fails can quantitatively reflect the enhancement of concrete strength by aggregate strengthening.

Silica micropowder is an important inorganic non-metallic material, which is mainly obtained from quartz sand or rock through a series of processes such as crushing, grinding, grading and purification. It usually has high purity and small particle size distribution. In this paper, the ultrafine silicon micropowder product was successfully prepared by flotation, acid leaching, ultrafine grinding, ion cleaning and modification using quartz product separated from gravity separation tailings of tungsten mine in Fujian as raw material. The results show that the main chemical composition (mass fraction) of ultrafine silicon micropowder is SiO₂ (99.820 0%), Fe₂O₃ (0.001 8%), Al₂O₃ (0.041 0%), the pH value of water extract is 7.08, the conductivity is 6.26 μS/cm, the concentration of Na⁺ is 0.24 ppm (1 ppm=10^-6), the concentration of Cl^- is 2.94 ppm, and the oil absorption value is 21.36 g/100 g. These indexes are better than the quality requirements of electronic grade active microsilicon powder of “Silicon dioxide powder for electronic and electrical industry”(SJ/T 10675—2002). This study provides ideas and methods for the effective utilization of high-value metal tailings in mines, and has positive significance for promoting resource recycling and environmental protection.

In order to achieve the goal of using red mud to remove SO₂ from flue gas, red mud and fly ash were used as raw materials, activated carbon as pore-forming agent, and sodium silicate as binder, and the dry desulfurization agent was prepared by extrusion and then calcination, and the desulfurization mechanism was explored. The effects of different pore-forming agent, binder addition and desulfurization temperature on the desulfurization performance of the desulfurizer were studied, the best mass ratio was determined to be m(red mud)∶m(sodium silicate)∶m(fly ash)∶m(activated carbon)=70∶20∶15∶10, and the desulfurization temperature was 250 ℃ to obtain the best desulfurization performance, with a penetration time of 163 min and a penetrating sulfur capacity of 10.484%. The results show that the removal of SO₂ by red mud desulfurizer mainly depends on the surface adsorption mechanism and the reaction mechanism between metal oxide and SO₂. The surface adsorption mainly depends on the pore size distribution, specific surface area, rich pore structure and surface active centers of desulfurizers. The metal oxides can play adsorption role and chemical reaction with SO₂, and the large amount of lattice oxygen and adsorbed oxygen contained in it can catalyze the chemical reaction and improve the efficiency of desulfurization.

In order to reduce the brittleness of high-strength gypsum, polyethylene fiber was used as toughening material, the effect of polyethylene fiber content on the property of high-strength gypsum was explored through compressive, flexural, uniaxial tensile and water absorption tests, the microscopic morphology of polyethylene fiber toughened high-strength gypsum was analyzed by SEM, and the mechanism of polyethylene fiber on the macroscopic property of high-strength gypsum was revealed. The results show that with the increase of polyethylene fiber content, the water absorption of high-strength gypsum increases, the compressive strength decreases, and the flexural strength and tensile properties show trend of decreasing first and then increasing. When the volume content of polyethylene fiber reaches 2.0%, the flexural strength and tensile properties are improved most obviously. Compared with the control group, the flexural strength of high-strength gypsum improves by 86.06%, the tensile strain increases by 4.45%, and the ultimate tensile stress increases by 102.78%. The incorporation of polyethylene fiber makes the high-strength gypsum exhibit excellent tensile strain hardening properties and the toughness is significantly improved. Based on the tensile test results, the tensile stress-strain curves of the polyethylene fiber toughened high-strength gypsum are regressed, and the tensile constitutive model is established, which can provide a reference for the property analysis of fiber toughened high-strength gypsum.

In order to verify the feasibility of yellow phosphorus slag produced in Yunnan Province as an supplementary cementitious material, this paper compared the grinding and cementitious properties of granulated blast furnace slag and yellow phosphorus slag, and analyzed and compared their properties as supplementary cementitious materials. The results show that granulated blast furnace slag and yellow phosphorus slag have similar chemical composition and mineral phase. After the same grinding time, the particle size distribution, specific surface area and microstructure of granulated blast furnace slag and yellow phosphorus slag are similar. The increase of specific surface area of granulated blast furnace slag and yellow phosphorus slag promotes the hydration of cement and improves the activity of granulated blast furnace slag and yellow phosphorus slag, and the activity of granulated blast furnace slag is higher than that of yellow phosphorus slag under similar specific surface area. The addition of granulated blast furnace slag and yellow phosphorus slag has a great contribution to the later strength of cement mortar. The later strength of cement mortar increases with the increase of specific surface area of granulated blast furnace slag and yellow phosphorus slag. When the specific surface area of granulated blast furnace slag and yellow phosphorus slag is 340 and 521 m²/kg, respectively, the 28 d compressive strength of cement mortar with 30% (mass fraction) granulated blast furnace slag and yellow phosphorus slag is 46.5 and 47.3 MPa, respectively, which is higher than that of pure cement mortar. When the specific surface area of granulated blast furnace slag and yellow phosphorus slag is 775 and 802 m²/kg, the 28 d compressive strength of cement mortar is 58.7 and 50.9 MPa, respectively. In general, yellow phosphorus slag is an available supplementary cementitious material with high activity in this study, but attention should be paid to the retarding effect of yellow phosphorus slag on cement-based materials.

In order to increase the replacing amount of waste rubber within concrete and to ensure its mechanical strength meet the designed standard, the paper investigated the effects of silica fume content and waste rubber content on the 28 d compressive strength, flexural strength and splitting tensile strength of concrete. The morphology of concrete was explained by using scanning electron microscopy (SEM), and the failure process was simulated by using ABAQUS finite element software at the microscopic level. The results show that the adding of waste rubber reduces the mechanical properties of concrete. The higher the waste rubber content is, the lower the mechanical properties is. Silica fume can improve the mechanical properties of rubber concrete, and the optimal content is 7% (mass fraction). The mechanical properties of concrete hybrid incorporating of 7% silica fume and 15% (volume fraction) rubber are consistent with the control one, and 28 d compressive strength, flexural strength and splitting tensile strength are 50.3, 3.56, and 2.64 MPa, respectively, meeting the designed requirements of C40 concrete, which are 24.2%, 13.4%, and 10.0% than those of concrete single doped with 15% rubber concrete. There are a lot of defects on the interface between rubber and cement mortar, and the higher the waste rubber is, the more the microscopic defects is. The adding of waste rubber leads to the micro-cracks transfer from the coarse aggregates interface to rubber particles, and the higher the rubber content is, the more the micro-cracks is. The incorporating of silica fume is effective in reducing the rubber particle interface cracks, and improve concrete strength.

In this paper, using red mud, fly ash and calcium carbide slag as the main raw materials, the composite cementitious test blocks of red mud-fly ash, red mud-calcium carbide slag, fly ash-calcium carbide slag binary systems, and red mud-fly ash-calcium carbide slag ternary system were prepared respectively. The size of gelling effect of red mud, fly ash and calcium carbide slag was compared with the compressive strength of the cementitious test blocks at different curing ages. The phase composition, molecular bond structure, microstructure and thermogravimetric characteristics of the cementitious test blocks were analyzed by XRD, FT-IR, SEM and TGA to study the hydration mechanism of different cementitious systems. The results show that the synergistic gelling effect of the ternary system of red mud, fly ash and calcium carbide slag is the largest. When the content of red mud, fly ash and calcium carbide slag is 35%, 30% and 35% (mass fraction) respectively, the 28 d compressive strength of the test block reaches 25.4 MPa. Compared with the binary cementitious system, the ternary cementitious system has higher hydration degree and more complex products. SEM analysis shows that the ternary cementitious system test block of sodium aluminate hydrate (N-A-S-H) and calcium aluminate hydrate (C-A-S-H) are interlinked with the raw materials to form a three-dimensional network structure, which makes the structure more dense and has better mechanical properties.

The comprehensive utilization of bulk solid waste is an important aspect of China's in-depth implementation of sustainable development strategy. Both red mud and coal gangue belong to China's bulk industrial solid waste, which have the characteristics of large amount, wide application, outstanding environmental impact and broad utilization prospects. In this paper, a solid waste-based admixture with red mud, coal gangue and lithium slag as raw materials was designed, and the composite cementitious materials were prepared by replacing cement with a solid waste-based admixture. The effects of the mix ratio of solid waste raw materials and the ratio of admixture instead of cement on the mechanical properties, chloride ion corrosion resistance, pore structure and microstructure of composite cementitious materials were investigated. The results show that although the solid waste-based admixture reduces the mechanical properties of the composite cementitious material, it can significantly improve the chloride ion corrosion resistance. The synergistic preparation of red mud, coal gangue and lithium slag optimizes the mineral phase composition of solid waste-based admixtures, so that the admixtures dissolve trace elements and form highly active minerals. In particular, the addition of lithium slag can further enhance the hydration activity of the composite cementitious material, improve its mechanical strength and chloride ion corrosion resistance. This study is expected to provide a theoretical reference for the development and application of solid waste-based admixtures.

In order to comprehensively utilize steel solid waste, this paper used steel slag, blast furnace slag, iron tailings and natural crushed sand as raw materials, NaOH and Na₂SiO₃ as activators to prepare concrete. The effects of mass ratio of steel slag-to-blast furnace slag, iron tailings replacement rate, alkali dosage and alkali modulus on the working and mechanical properties of concrete were investigated. Based on microstructural analysis and pH test, the corresponding hydration mechanisms of alkali-activated steel solid waste concrete were revealed. The results show that the addition of iron tailings can improve the gradation of aggregates particles and enhance the overall compactness of concrete. The activators promote the dissolution of active minerals of steel slag and blast furnace slag, and speed up the hydration reaction process of concrete. The inclusion of steel slag can provide abundant Ca²⁺ for the formation of C-S-H gel, C-A-S-H gel and Ca(OH)₂ crystal. When the mass of steel slag-to-blast furnace slag is 1∶9, the iron tailing replacement rate is 45% (mass fraction), the alkali dosage is 6% (mass fraction) and the alkali modulus (molar ratio of SiO₂ and Na₂O) is 1.4, the 28 d compressive strength of alkali-activation steel solid waste concrete reaches 47.6 MPa.

Granulated blast furnace slag (BFS) powder and fly ash (FA) in industrial waste have become the main admixtures for preparing Portland cement due to their typical pozzolanic properties. Whether recycled brick powder (RBP) and recycled concrete powder (RCP) in construction solid waste can be mixed with BFS and FA to prepare active admixtures is an important way to expand the utilization of multi-source solid waste resources. In this study, RBP, RCP, FA and BFS were used as raw materials to prepare admixtures by wet ball milling. The compressive strength test of binder was carried out with the content of the admixture as the variable, and activity of admixture was evaluated by the pozzolanic specific strength method. The hydration products were analyzed by XRD, TG-DTG, SEM and EDS. The results show that the admixtures prepared from four types of solid waste powders can effectively replace a portion of cement. The compressive strength of cement mortar containing admixtures can reach up to 74.2 MPa at 90 d. Due to the pozzolanic reactivity of RCP and RBP, the diffraction peak intensity of the hydration product CH phase decreases and the C-S-H peak widens after the reaction. Ca²⁺ and Si²⁺ in RCP and RBP promote the activation of siliceous and aluminum minerals in FA and BFS. The optimal mass fractions of each component in the active admixture prepared by the synergistic effect of active silicon and aluminum minerals are 15% RBP, 15% RCP, 15% FA, and 5% BFS. The application of active admixtures not only helps improve the utilization efficiency of various solid waste materials, but also helps reduce the dependence of the construction industry on ordinary cement.

In order to study the durability of polyvinyl alcohol (PVA) fiber waste glass powder concrete under sulfate dry-wet cycle, two kinds of particle size waste glass powder were used to replace part of cement in concrete. At the same time, the volume content of PVA fiber was changed. The sulfate dry-wet cycle test was designed, and compressive strength and flexural strength of waste glass powder concrete after dry-wet cycle were measured. The microstructural characteristics of PVA fiber waste glass powder concrete were explored by SEM and EDS. Finally, the durability degradation model based on the Weibull function was established to predict concrete life. The results indicate that when the particle size of waste glass powder is (30,75] μm, the performance of resisting sulfate corrosion is relatively good. PVA fibers play an effective role in hindering the internal cracks of concrete. With the increase of PVA fiber content, the performance of resisting sulfate corrosion of PVA fiber waste glass powder concrete increases, and it shows the best performance of resisting sulfate corrosion when the PVA fiber content is 1.0% (volume fraction). The durability degradation model predict that the maximum service life of waste glass powder concrete with PVA fiber volume content of 1.0% can reach 224 d under the dry-wet cycle of sulfate solution.

To apply construction waste to road engineering construction, the variation law and multiple influencing factors of the road performance of cement stabilized construction waste recycled materials with different mix ratios were explored. The multiple construction waste content (volume fraction of 20%, 40%, 60%, 80%, and 100%), three brick concrete ratios (brick concrete volume ratios were 1∶1, 1∶2, full concrete) and two cement content (mass fraction of 4% and 5%) were used for mix ratio design. A systematic study was conducted on the road performance and its variation patterns through compaction, unconfined compressive strength, splitting strength tests, water stability, frost resistance and dry shrinkage tests. The grey relational analysis algorithm was used to analyze the degree of influence of different mix ratio variables in aggregates on road performance. The results indicate that with the increase of construction waste content, brick concrete ratio and cement content, the unconfined compressive strength, splitting strength, water stability and frost resistance of recycled materials at 7 and 28 d all decrease. The dry shrinkage coefficient increases with the increase of cement content, and the correlation degree between the mix ratio variables and road performance from high to low is cement content, construction waste content and brick concrete ratio. When the cement content is 4%, the construction waste content is 80% and the brick concrete ratio is 1∶2, it can still meet the grassroots requirements of secondary and lower level highways for medium and light traffic.

A series of chromium-iron spinel black matte glazes were prepared at 1 200 ℃ by adjusting the ratio of chromium to iron in chromium-iron spinel. The influences of black pigments prepared under different iron-chromium ratios on the coloration of matte glazes and the coloration mechanism were studied. The results show that when the pigment formula is m(Fe₃O₄)∶m(Cr₂O₃)=80∶20 (mass ratio), the glaze is the darkest, and its L^*, a^* and b^* values are 15.90, -0.75 and 0.94, respectively. The n(Fe³⁺)∶n(Fe²⁺)=60.38∶39.62 (molar ratio) in the glaze, the content of Fe²⁺ is the highest, which is conducive to the appearance of black. The glaze is black because of the superposition of the optical effects of Fe³⁺, Fe²⁺ and Cr³⁺ under visible light. The four-coordinated Fe³⁺ is brownish red, the six-coordinated Cr³⁺ is green, and the six-coordinated Fe²⁺ is green. The superposition of the three colors can absorb all the wavelengths of visible light and make the glaze appear black. The main crystal phase in the black matte glaze is wollastonite phase. Wollastonite grains are randomly distributed in the glaze, and the grain size is within 10 μm, which produces a matting effect and makes the glaze produce a soft matte texture.

Boron nitride (BN) fiber is an important reinforcement for the preparation of ultra-high temperature ceramic-based wave-transparent composites, and it is a key material for the development and application of high Mach number aircraft wave-transparent radomes. Therefore, through investigation into the relationship between the microstructure and mechanical properties of BN fibers is particularly important for the progress of new-generation equipment. In this study, BN precursor fibers were prepared using the melt spinning method, and the structure and properties of BN fibers during the inorganic and ceramicization heat treatment were systematically characterized. The BN precursor fibers were converted into inorganic amorphous BN intermediate fibers, which were subsequently sintered at high temperatures to yield microcrystalline BN fibers, ultimately forming a structure composed exclusively of B—N—B hexagons. The study investigated the alterations in microstructure, structural transformation, crystallinity, and mechanical properties of the fibers during heat treatment under N₂ and NH₃ atmospheres. The results indicat that when NH₃ is employed as the reaction atmosphere, the intermediate fibers have a dense structure, containing BN microcrystals (t-BN) with distinct lattice fringes, and the carbon content is only 0.09% (mass fraction). The tensile strength and elastic modulus of BN-10NH-16 fibers ceramicization reaches 832.14 MPa and 74.88 GPa, respectively. When N₂ is employed as the reaction atmosphere, the cross-section of the BN intermediate fibers exhibit obvious pores and defects, but no microcrystals are formed, and the carbon content remaines at 18.00% (mass fraction). The tensile strength and elastic modulus of the BN-10N-16 fibers after ceramicization reaches 383.98 MPa and 71.73 GPa, respectively. XRD and HRTEM results indicate that the crystallinity of inorganic BN-10NH-16 fibers are significantly improved at 1 600 ℃ under NH₃ atmosphere, and there is a certain degree of orientation along the axis direction of fibers, which thereby significantly enhances the mechanical properties of the fibers. Additionally, the relationship between microstructural defects and the mechanical properties of the fibers is verified by Weibull distribution fitting, providing an important reference for the subsequent preparation of high-performance BN fibers.

Based on pressureless sintering technology, 6Al₂O₃-4Y₂O₃, 2MgO-2Al₂O₃-5SiO₂, 3Al₂O₃-2SiO₂ and B₄C were used as sintering aids to prepare high density silicon carbide (α-SiC) with low content of sintering aids in this study. The phase, microstructure and mechanical properties of α-SiC prepared by different sintering aids and sintering process were analyzed. The results show that in terms of liquid phase sintering, adding 4.0% (mass fraction) 6Al₂O₃-4Y₂O₃ sintering aid, the α-SiC prepared by sintering at 1 850 ℃ has the best performance, and the density reaches 3.19 g·cm^-3. However, at 1 300 ℃,the bending strength and fracture toughness of α-SiC prepared by this process decrease by 34.9% and 7.4%, respectively. In terms of solid phase sintering, the density of α-SiC prepared by adding 0.3% (mass fraction) B₄C sintering aid at 2 000 ℃ reaches 3.14 g·cm^-3, and it has excellent mechanical properties at room temperature and 1 300 ℃. The microstructure of α-SiC prepared by solid phase sintering and liquid phase sintering is compared and analyzed by DF-TEM. The mechanism of the evolution of bending strength and fracture toughness of α-SiC prepared by adding 6Al₂O₃-4Y₂O₃ and B₄C sintering aids at room temperature and high temperature is preliminarily revealed.

Architectural glass exhibits excellent transparency and reflective characteristics, which often makes it difficult for birds to distinguish during flight, leading to fatal collisions or severe injuries. It is estimated that hundreds of millions of birds are killed annually by glass curtain in North America. As a critical migration route for migratory birds in China, the potential threat posed by the built environment to birds is even more serious. Therefore, this paper focuses on the phenomenon of bird collisions with architectural glass, discusses the causes and characteristics of such collisions, while combines existing research results to review the research status of the formation of haze patterns on glass surface and the preparation of ultraviolet reflective flim on glass surface, and summarizes and analyzes the application status of bird impact prevention measures at home and abroad, aiming to propose scientific strategies and reference for protecting biodiversity and looks forward to the future development of bird-friendly glass technology.

To investigate the risk of nickel sulfide particles inducing the spontaneous breakage of tempered glass, this study introduced the concept of "equivalent critical volume expansion" and employed numerical simulation to analyze the effects of particle size, shape, and location on spontaneous breakage of tempered glass. The phase transition of nickel sulfide was modeled through thermal expansion induced by temperature increase, allowing quantitative analysis of phenomena breakage of tempered glass. Stress and temperature variations surrounding the nickel sulfide particles were examined to determine the distribution of maximum principal stress and the volume expansion of nickel sulfide particles at the onset of spontaneous breakage. The findings indicate that the risk of spontaneous breakage increases as the nickel sulfide particle moves closer to the center of tempered glass, while spontaneous breakage is nearly absent when nickel sulfide particles are located in compressive stress zones. The spontaneous breakage risk intensifies with nickel sulfide particle shapes approaching prolate spheroids, whereas in oblate spheroids, the risk must be assessed based on the orientation of the particle's major axis. For safety considerations, it is recommended that tempered glass be classified as having a high risk of spontaneous breakage when nickel sulfide particle size exceeds 0.12 mm.

To extend the service life of cordierite-mullite saggar in the lithium-ion battery ternary cathode material (LiNi_xCo_yMn_1-x-yO₂, LNCM) industry, silicon powder was introduced into cordierite-mullite samples and the effect of silicon powder content on the sintering performance, pore size distribution, mechanical properties, thermal shock stability, and corrosion resistance against LNCM was investigated. The results indicate that when the silicon powder content increases from 0% (mass fraction, the same below) to 5%, the liquid phase in the samples increases at high temperatures, promoting mass transport and the sintering process. The bonding between the aggregate and the matrix is enhanced, leading to a decrease in apparent porosity and pore size, while the strength and thermal shock resistance are improved. When the content of silicon powder increases to 7%, the interstices between the aggregate and the matrix are increased because of the significant shrinkage of the matrix, due to excessive liquid phase formation. Hence, the strength and the thermal shock resistance of samples are decreased. LiAlSiO₄ and (Mg, Ni, Co, Mn)Al₂O₄ composite spinel are generated in the corrosion reaction between the LNCM and sample. The formation of LiAlSiO₄ is accompanied by approximately 32% volumetric expansion, leading to cracking and spalling of samples. As the silicon powder content increases from 0% to 5%, the migration channel for LNCM is decreased due to the reduction in apparent porosity and pore size, significantly improving the corrosion resistance. When the content of silicon powder increases to 7%, the pore size of samples increases but the corrosion resistance is still improved slightly due to the formation of a continuous dense structure in the matrix. Overall, the sample with 5% silicon powder exhibits the best performance: the apparent porosity is 23.6%, with average pore sizes of 1.5 and 1.7 μm at the edge and center, respectively. The cold modulus of rapture and residual strength ratio after three times thermal shocks are 15.6 MPa and 86.1%, respectively, with an average corrosion layer thickness of 685 μm.

According to the characteristics of different light absorption curves of different types of solar photovoltaic cells, the corresponding anti-reflection films were designed respectively. The transmittance of films under different models was simulated by TFcal software. The films and key parameters suitable for different types of cells were obtained. The optical transmittance of films was tested by ultraviolet-visible-infrared spectrophotometer. The electrical properties of c-Si solar cells covered with anti-reflection film were tested by xenon lamp solar simulator and digital source meter. The results show that the optimal anti-reflection films of different solar cells is different. The highest average transmittance of the prepared film in 380~1 200 nm is 93.1%. When the film with an average transmittance of 92.5% is used, the battery obtains a relatively better battery efficiency, and the output power is 1.129 771 mW.

In order to study the durability of solidified soil in dry environment, bentonite and glass fiber were used to improve the cement solidified soil, and the crack evolution characteristics and strength deterioration of solidified soil in dry environment were studied. The influences of bentonite content and fiber content on crack index and unconfined compressive strength of solidified soil were analyzed, and the microstructure degradation mechanism of solidified soil was studied by scanning electron microscope. The results show that the addition of bentonite and fiber to solidified soil can significantly improve the durability of solidified soil in dry environment. When the bentonite content is 6% (mass fraction) and the fiber content is 0.3% (mass fraction), the improvement effect of solidified soil is the best. The unconfined compressive strength loss rate of specimen with curing age of 28 d after drying test is only 3.6%, and there is still a high residual strength after the peak stress, and there is no obvious crack on the surface of specimen. The evaporation of water in dry environment leads to the increase of porosity and pore volume of specimen, and the decomposition of hydration products, resulting in cracking and strength deterioration of specimen.

In order to study interlayer bonding state of cement stabilized base and the influencing factors of the performance of double-layer continuous paving interlayer, BISAR 3.0 software was used to calculate the mechanical response of pavement structure under the condition that the contact between the interlayer of base was completely continuous, partially continuous and close to smooth. Through direct shear and direct pull-out tests, the effects of water-stabilized mixture gradation, interlayer cement slurry dosage, water-cement ratio and lower base compaction on the mechanical properties of double-layer continuous paving base were explored. The results show that improving the bonding degree between upper and lower base interlayer can significantly improve the fatigue life of upper base, improve the stress state of overall pavement structure, and improve durability and service life of pavement. The interlayer shear strength of coarse gradation is the largest, but the tensile strength decreases slightly. The interlayer strength of upper and lower base can be enhanced by increasing coarse aggregate dosage. When the interlayer cement slurry dosage is 55 g (0.311 g/cm²) and the water-cement ratio is 1.0∶1.5, the interlayer bonding strength of double-layer cement stabilized base is the largest. The shear strength and tensile strength of interlayer increase first and then decrease with the increase of compaction degree of lower base. It is suggested that the compaction degree of lower base should be controlled at 93%~95%, then the paving and rolling of upper base can be carried out.