The effect of styrene acrylic (SA) copolymer on the early hydration of calcium sulphoaluminate-anhydrite composite was investigated by calorimetry, X-ray diffraction, thermogravimetic analysis, scanning electron microscopy, and inductively coupled plasma-optical emission spectroscopy. The results show that SA can delay the hydration process, reduce the content of ettringite (AFt), single sulfur calcium sulphoaluminate hydrate (AFm) and Al(OH)₃ (AH₃) in the accelerated hydration period, and promote the reaction of AH₃ with anhydrite and calcium hydroxide to form AFt as well as the transformation of AFt to AFm in the late hydration period. Also, SA can rapidly reduce the surface tension of the pore solution, and the surface tension tends to be stable within the hydration reaction. SA can increase the pH value of the pore solution, increase the concentration of OH^- and affect the concentration of Ca²⁺, SO₄^2- and [Al(OH)₄]^- in the composite, and decrease the ion concentration and the precipitation rate of hydration products at the initial stage of hydration, thus delaying the hydration process and reducing the hydration products.

A composite of porous carbon coated Li₄Ti₅O₁₂ was prepared by a hydrothermal synthesis and high-temperature activation method. The microstructure and electrochemical properties of the composite were investigated. The results show that Li₄Ti₅O₁₂ is completely coated on the porous carbon layer. Meanwhile, the surface pores of Li₄Ti₅O₁₂@porous C composite are evenly distributed, and the carbon layer thickness is approximately (8.5±3.6) nm. The discharge capacity at first cycle is 363 mAh/g, which is approximately twice greater than that of pure Li₄Ti₅O₁₂. The AC impedance value of Li₄Ti₅O₁₂@porous C composite decreases, which is only the half of that of pure Li₄Ti₅O₁₂. The discharge specific capacity of Li₄Ti₅O₁₂@porous-C composite is 251 mAh/g and the retention rate is 97.7 % after 200 cycles (i.e., the specific capacity of pure Li₄Ti₅O₁₂ is 143 mAh/g and the retention rate is 94.7%), the discharge specific capacity is nearly doubled, especially when the rate test is carried out at different discharge rates. The reversible capacity is twice greater than that of Li₄Ti₅O₁₂. The porous carbon coated modification of Li₄Ti₅O₁₂ can increase the specific surface area and the electron transfer rate for the higher electrochemical properties.

Lithium-aluminosilicate glasses with different zirconia (ZrO₂) concentrations were prepared by a melting-quenching method. Glass slices were treated using a two-step chemical strengthening method below glass transition temperature (T_g). The effect of ZrO₂ addition on the glass stability, hardness and chemical strengthening performance was investigated. The results show that the T_g increases with the increase of ZrO₂ concentration in the range of 0-5% (in mole fraction). The absence of crystallization peaks indicates these glasses are rather stable. An appropriate addition of ZrO₂ can promote the Li⁺-Na⁺ ions exchange and increase the layer depth. The surface compression stress (σ_c) increases with the increase of the ZrO₂ concentration and reaches a maximum value of 1 055.6 MPa at 4% ZrO₂ concentration. The center tension firstly increases and then decreases slightly with the increase of the ZrO₂ concentration, indicating that these glass samples have a good shock resistance. The addition of ZrO₂ has little effect on the hardness of glasses after chemical strengthening. Although the addition of ZrO₂ decreases the crack resistance, these glasses still have a good crack resistance performance after chemical strengthening.

Phosphosilicate glasses are widely used in optical fiber, biological materials and other fields because of their excellent optical properties and biological activity. The influence of Li₂O content on the microstructure and diffusion properties of Na₂O-Al₂O₃-SiO₂-P₂O₅ glass was investigated via molecular dynamics simulation, and the relationship among the microstructure, Vickers hardness and diffusion coefficient was analyzed. The results show that the degree of phosphorus network polymerization (Q^P) increases with the substitution of Li₂O for Na₂O, and the hardness increases with the increase of Q^P. The self-diffusion of Li⁺ ions is greater than that of Na⁺ ions, indicating that Li⁺ ions are easier to diffuse rather than Na⁺ ions. The potential barrier of Li⁺ ions decreases with the increase of Li₂O. Li₂O is beneficial to the substitution of Na₂O for the diffusion of Li⁺ ions.

To investigate the effects of replacement rate and sample size on the direct shear performance and damage of recycled aggregate concrete (RAC), 45 RAC specimens were manufactured. The failure modes of RAC with different sizes were characterized, and the effects of replacement rate and specimen size on the direct shear performance and damage constitutive model of RAC with different sizes were investigated via direct shear tests. The results show that the peak deformation and ductility coefficient have a size effect, the damage development rate of natural concrete becomes slow, and the damage development rate of RAC becomes faster. The peak deformation firstly decreases and then increases, while the ductility coefficient firstly increases and then decreases with the increase of the replacement rate. The damage development law does not have a linear relationship with the replacement rate. The constitutive model can well reflect the shear load-deformation relationship and the damage evolution process of the RAC with different sizes.

The mechanical properties, hydration process and microstructure characteristics of the calcined hydrotalcite modified cementitious material at different fly ash contents were analyzed. Based on the results by the compressive strength test calcined hydrotalcite can greatly improve the compressive strength of cement-fly ash mortar. The phase composition of hardened cement paste was characterized by X-ray diffractionand and thermogravimetric analysis. The results show that calcined hydrotalcite can promote the hydration of cement-fly ash cementitious materials, thereby increasing the content of hydration products. It is incidiacted that calcined hydrotalcite can accelerate the dissolution of fly ash, and its nucleation effect is beneficial to the formation of hydration products.

To quantify a relationship between the accelerated calcium leaching effect and the concentration of nitric acid solution ranging from 0.01 to 0.50 mol/L, leaching experiments and numerical simulation were conducted for cement paste, mortar and concrete specimens at a water-cement ratio of 0.50, and the evolutions of the macro- and micro-leaching indicators were analyzed. The results show that the proportional coefficients in Fick's diffusion law based on leaching depth and cumulative relative leached calcium ion exhibit a linear and negative exponential growth relationship with the concentration of nitric acid solution. The diffraction peak of calcium carbonate at the same depth of each leached paste specimen linearly decreases. The equivalent accelerated diffusion coefficients of cement paste, mortar and concrete are linearly proportional to the concentration of nitric acid solution, and the acceleration ratios are 3.9×10³, 1.6×10³ and 1.0×10³ times of the concentrations (measured in mol/L), respectively. For cement paste with a water-cement ratio of 0.50, acceleration ratios of 6.00 mol/L ammonium nitrate, 0.50 mol/L nitric acid, 6.00 mol/L ammonium chloride and deionized water are 4 507, 2 018, 464 and 47, respectively. The equivalent accelerated diffusion coefficient of cement paste is 2.3 times greater than that of the concrete at the same water-cement ratio. If the concentration of chemical immersion solution is too high, the calcium dissolution-diffusion process will deviate from the dissolution mechanism in fresh water environment. When nitric acid solution is used for an accelerated calcium leaching experiment, an appropriate concentration is 0.10 mol/L.

Corrosion behavior and evolution of steel reinforcement in simulated concrete pore solutions subjected to different corrosive ions (i.e., chloride, sulfate, chloride-sulfate, and simulate sea water) were investigated. Corrosion products induced with chloride and sulfate ions were also analyzed, respectively. The results show that the presence of sulfate ions in co-existence scenario of chloride-sulfate ions lead to a lower polarization resistance and a higher corrosion current density. The steel corrosion potential is correlated to the polarization resistance evolution as a power function relationship. Corrosion products induced by chloride and sulfate ions depicts a slight difference, mainly containing γ-FeOOH, α-FeOOH, Fe(OH)₃, Fe₂O₃ and FeO.

To ascertain the influences of bentonite and its content on the printability of 3D printing mortar, the extrudability of mortar was evaluated via fluidity, and its buildability was evaluated by height retention rate and penetration resistance. Also, the rheological behavior of cement pastes with bentonite was characterized via dynamic and static shear tests. Effects of bentonite and its content on the printability of mortars were analyzed via rheology. The results show that the fluidity of printable mortars is linearly correlated to the plastic viscosity of cement pastes and logarithmically to the dynamic yield stress of cement pastes. Besides, there is an exponential relationship between the height retention rate of printable mortars and the static yield stress of cement pastes. The addition of bentonite in the mortar increases the plastic viscosity and dynamic yield stress of cement pastes, resulting in a decrease in the extrudability of mortar. Also, the addition of bentonite improves the static yield stress and structural rebuilding rate of cement pastes, thereby improving the buildability of mortar. Therefore, appropriate amount of bentonite can make the mortar maintain good extrudability while improving its buildability. A width ratio between the top and bottom layers of the printed sample with 2% bentonite is 0.96.

The hydration degree and mechanical properties of ultra-high performance concrete (UHPC) specimens with hybrid steel fibers cured in air and hot water (1 d, 60℃ hot water + 2 d air), respectively, were investigated via ignition loss tests and uniaxial tensile and compressive tests. Also, the surface cracking characteristics of tensile specimens were characterized by digital image correlation technique and optical microscopy, and the microstructures were analyzed by scanning electron microscopy. The results show that compared with the results obtained in air curing, hot water curing accelerates the hydration reaction progress of the UHPC matrix, and an increase in temperature mainly contributes to the promotion of hydration reaction, thus improving the initial cracking, tensile and compressive strength of the UHPC specimens in hot water curing. However, the tensile strain capacity changes slightly. In general, the maximum crack width of the specimen decreases, the matrix becomes denser, and the interface bonding between the fibers and the matrix is stronger. The tensile strain of UHPC increases with the increase of fiber content, in which the tensile strains of the specimens with 2.5% (volume fraction) of fibers (a ratio of long fibers to short fibers is 1.25∶1.25 and 1.5∶1.0, respectively) are more than 2 ×10^-3, the specimen with 1.5% long fibers and 1.0% short fibers produces more tensile cracks with the width of < 50 μm in hot water curing. The uniaxial tensile strains predicted by DIC are in reasonable agreement with the strains measured.