CVDZnS samples were prepared by a chemical vapor deposition method at different deposition temperatures (i.e., (650±10), (670±10), (700±10) ℃ and pressures (i.e., (5 000±200), (7 000±200), (9 000±200) Pa as well as a H₂S flowrate of (2±1) L/min and an argon flowrate of (35±2) L/min. The CVDZnS samples were analyzed by X-ray diffraction, metallographic microscopy and Fourier transform infrared spectroscopy, microscopic grain morphology and infrared transmittance measurement at 2-15 μm. Based on the XRD characterization, CVDZnS mainly exists in the form of cubic phase with a small amount of hexagonal phase and the preferential orientation of deposition growth is s(111). The metallographic analysis indicates that the average grain size increases with the increase of temperature when the deposition pressure is (5 000±200) and (7 000±200) Pa, and the maximum average longitudinal grain size is 15.5 μm. The bending strength test data show that the ratio of average longitudinal grain size to average transverse grain size is closer to "1", which is more advantageous to increase the bending strength of materials. In addition, the CVDZnS prepared at (670±10) ℃ and (7 000±200) Pa can effectively improve the average transmittance of 2-5 and 7-10 μm (i.e., 72.15%) and reduce the absorption at 6.0 μm.

A mullite-cordierite saggar was prepared with mullite, cordierite, α-Al₂O₃, talc and Kaolin clay, and the room-temperature mechanical properties, thermal shock resistance and erosion mechanism of saggar in sintering process of LiCoO₂ were investigated. The results show that the better mechanical properties and thermal shock resistance of the saggar can be obtained when sintering at 1 350 ℃. The bending strength of sample is 11.18 MPa and its residual strength retention rate after three cycles of thermal shock is 44.8%. In the process of sintering LiCoO₂, a mullite-cordierite saggar is attacked by Li₂O, producing LiAlSiO₄, Li₄SiO₄ and LiAlO₂. Li₂O diffuses into the sagger along the pores, and the structure of the permeation layer is denser after the reaction, which can hinder Li₂O from further attacking the sagger, thus giving a good erosion resistance of mullite-cordierite sagger.

The influence of hydroxyethyl methyl cellulose (HEMC) on the early hydration of Portland cement and rapid-hardening calcium sulfoaluminate cement (CSA) was investigated by acoustic and electroacoustic spectrometer and low-field NMR instrument. The water retention and air void content of fresh mortars were analyzed. The results show that regardless of cement variation, the water retention and air void content are improved after the addition of HEMC. The change of zeta potential is related to cement type. For the Portland cement paste, the addition of HEMC greatly shortens the time of zeta potential becoming electropositive, and the absolute value of ζ potential for rapid-hardening CSA paste decreases slightly. In addition, the T₂ distribution of HEMC containing cement pastes also appears a relaxation peak at 100-1 000 ms. Such a peak disappears after 3-d hydration for the Portland cement, while it only disappears in 120 min for rapid-hardening CSA, indicating that HEMC exerts a weak adsorption on the surface of rapid-hardening CSA particles. Unlike the retardation effect of HEMC on the Portland cement hydration, HEMC hardly affects the early hydration heat release of rapid-hardening CSA.

Effects of water-binder ratio, polycarboxylate superplasticizers (PCEs) with different molecular structures, super-absorbent polymer (SAP) and an anionic viscosity modifying agent (VMA) on the rheological properties of mortar were investigated. The results show that increasing the water-binder ratio simultaneously reduces the yield stress and plastic viscosity of mortar and increases the fluidity retention capacity. The addition of PCE reduces the yield stress of mortar and the steric hindrance induced by the side carbon chains is one of the main reasons for the dispersion effect of PCE. The side carbon chains inhibit the adsorption of PCE on the surface of cement particles. Increasing the length of the side chains of PCE has little effect on the initial rheology. SAP increases the yield stress and plastic viscosity of mortar by reducing its free water content, and its action mechanism is the same as reducing the water-binder ratio. VMA improves the yield stress of mortar due to the bridging effect at low dosages, but has little effect on the plastic viscosity. At high dosages, the bridging effect of VMA weakens but the viscosity of liquid phase greatly increases, thus decreasing the enhanced effect on the yield stress of mortar and greatly increasing the plastic viscosity of mortar.

The molecular size of cellulose ether in solution was determined via dynamic light scattering (DLS), and the adsorption of cellulose ether on cement particles was determined by total organic carbon content (TOC). The results show that the particle size of cellulose ether in solution decreases with the increase of concentration and tends to a constant value, which can be called as undisturbed diameter. There exists a correlation between the measured adsorption of cellulose ether from TOC and theoretical adsorption of single layer cellulose ether in the state of dense packing on the surface of cement particles calculated from its undisturbed diameter and the Blaine specific surface area of cement. Therefore, cellulose ether is most probably adsorbed on the surface of cement particles with its undisturbed diameter, which is independent of cement type obtained.

The interfacial interaction between defoamer and air entraining agent was investigated by calculating the composition of mixed interfaces, the interaction parameter (β), and the free energy of additional adsorption and comparing the solution and hardened mortar performance of defoamer and air entraining agent in various proportions. The results show that compounding a suitable defoamer in a certain proportion into air entraining agent increases the interfacial free energy of the bubbles, resulting in a decrease in the stability of the foam and the air content of the mortar. The defoamer can also effectively reduce the air-void diameters and spacing factors of the hardened mortar, and improve the compressive strength of the mortar.

A mechanical model of cement and emulsified asphalt mortar (CA) from four different levels (i.e., cement hydration products, cement gel skeleton, cement asphalt composite system and CA mortar) was proposed based on the microscopic experimental results by backscatter electron imaging and X-ray diffraction and the Hashin composite ball model. The relationships among the elastic modulus of CA mortar, compressive strength f and composition parameters were investigated. The results show that the volume fraction of cement hydrate phase is an important parameter affecting the CA mortar elastic modulus and the compressive strength f. When asphalt is regarded as a pore or a low modulus component, the static elastic modulus of the CA mortar and the volume fraction of cement hydrate, compressive strength f and gel-space ratio all have a power function relationship > 0.8. The cement hydrate in the CA mortar is still a continuous phase and constitutes the composite gel skeleton, asphalt interspersing among them, and the contribution of asphalt to the CA mortar strength and elastic modulus is relatively low.

Effects of aspect ratio and volume fraction of straight steel fiber on the modulus of elasticity (MOE), compressive strength, and flowability of ultra-high-performance concrete (UHPC) were investigated. The results show that the MOE and compressive strength of UHPC increase and the flowability of the fresh UHPC decreases with the increase of fiber volume and fiber aspect ratio. Steel fiber has both positive and negative effects on the MOE of UHPC. The positive effect of steel fiber is due to the high elastic modulus of steel fiber itself. The negative effect is caused by the decrease of the MOE of UHPC matrix due to the decrease of the flowability of fresh UHPC and the increase of the porosity and the inner defects after the fibers adding into the matrix. A semi-empirical formula was proposed for predicting the MOE of the UHPC based on the experimental data, comprehensively considering the positive and negative effects of fibers. It is indicated that the MOE of the UHPC could be strongly correlated to the compressive strength.

The mechanical properties and flexural toughness behaviors of steel fiber reinforced shotcrete containing different liquid setting accerlerators were evaluated by a three-pointing loading method. To clarify the working mechanism of liquid setting accelerators on the toughness properties of steel fiber, the early-age strength development and steel fiber-cement matrix interface area micromorphology of steel fiber reinforced mortar with the similar material composition were investigated. The results show that the long-term mechanical strength of steel fiber reinforced shotcrete with alkali-free accelerator is greater than that with alkaline setting accelerator, thus leading to a full loading-deflection curve and better toughness enhancement effect of steel fiber. For the early-age strength development, short prismatic ettringite and needle-like C-S-H gel appear after introducing alkali-free setting accelerator, thus inducing the better bonding strength between steel fiber and cement matrix and improving the initial support capacity of steel fiber reinforced shotcrete.

A reactive powder concrete (RPC) matrix with a low water to cement ratio of 0.21 was prepared. The hydration of the RPC matrixes under long-term hydrothermal condition was investigated. The insoluble matter of the RPC matrix was examined to characterize its hydration level. The structural property of the RPC matrix was characterized using the Vickers hardness meter. The phase composition and morphology of the RPC matrix were characterized using X-ray powder diffraction and scanning electron microscopy/energy dispersive spectrometry. Under the hydrothermal condition, the hydration level of the RPC matrix increases during the autoclaved curing for 0-96 h, and the Vickers hardness of the RPC matrix also increases. The hydration rate of the RPC matrix is rather low, and the hydration of the clinker in the matrix becomes stopped during the long-term autoclaved curing (i.e., 168-312 h). In addition, there are a few crystalline hydrates in the RPC matrix cured for long-term, and the flocculent calcium silicate hydrates gel cannot be transferred to their crystalline forms due to the lack of space for the crystallization. The RPC matrix with a low water to cement ratio has a great stability under the long-term hydrothermal condition and a promising potential to be used as nuclear waste keeping materials.