Three mordenites with different morphologies (i.e., fiber bundle, regular fiber and flaky) were synthesized via the introduction of cyclohexylamine and hexamethyleneimmonium, respectively. The crystal form, morphology, pore structure and acidity of the samples were characterized by X-ray diffraction and N₂ physical adsorption, scanning electron microscopy and NH₃ temperature-programmed desorption, and the alkylation performance evaluation and regeneration experiments were carried out. The experimental results show that all three mordenites have a great catalytic activity, and the catalyst life of the flaky mordenite can reach 26 h, which is better than that of the fiber bundle mordenite for 5 h and the regular fibrous mordenite for 3 h. The fiber bundle and regular fibrous mordenites can have a selectivity to 2-substituted linear alkylbenzene of more than 75%, and the product selectivity of flaky mordenite can reach more than 50%, which is superior to the existing technology for linear alkylbenzene production. The catalyst regeneration rate is opposite to the catalyst deactivation rate. The three mordenites with fiber bundle regular fiber and flaky morphologies have the maximum catalytic activities of fresh catalysts after regeneration of 8, 11 h, and 5 h, respectively.

A ceramic slurry with a solid content of 57% (in volume fraction) was firstly prepared with α-Al₂O₃ of 92% (mass fraction) and silica fume of 8% as main raw materials, aluminum dihydrogen phosphate of 2.5% as a binder and sodium hexametaphosphate of 0.2% as a dispersant in the presence of Y₂O₃, and then the formed specimen was sintered at 1 600 ℃ for 3 h. The results show that the addition of Y₂O₃ has little effect on the printing properties of ceramic slurry. At high temperatures, Y₂O₃ reacts with Al₂O₃ to form YAG, and promotes the reaction of Al₂O₃ with SiO₂ in the specimen, thus increasing the specimen strength. A rate of the properties change after sintering decreases, and even the slag resistance decreases when the amount of Y₂O₃ addition exceeds 1.2%. The cold compressive strength is 230.2 MPa at the optimal amount of Y₂O₃ addition of 1.2%. For slag resistance, in addition to the densification of the high melting point YAG phase and the solid phase, a dense protective layer is formed on the inner wall of the crucible, thus enhancing the resistance to the penetration of glass melt. It is indicated that the addition of Y₂O₃ is beneficial to printing the specimens with a high strength and a good slag resistance.

Low carbon alumina zirconia carbon (Al₂O₃-ZrO₂-C) slide gate was designed with graphene nanosheets. The morphology of graphene nanosheets was characterized by atomic force microscopy and transmission electron microscopy. The phase composition and microstructure of the fabricated refractories were examined by X-ray diffraction, scanning electron microscopy and energy disperse spectroscopy. The results show that the GNSs can effectively improve the properties of slide gate refractories by filling the micropores and promoting the formation of silicon carbide whisker between particles. As 1.5% GNSs/Al₂O₃ composite powders are added instead of carbon black, the slide gate shows a better oxidation resistance and ensures the strength and thermal shock stability.

Effect of Al on the spinel evolution within Al₂O₃-MgO refractories in nitrogen at 1 600 ℃ was investigated. The results show that Al can markedly change the composition, morphology and reaction path of spinel phase within Al₂O₃-MgO refractories. Without Al addition, MgO reacts with Al₂O₃ to form spinel, and then spinel reacts with Al₂O₃ encompassed by itself to form once-rich-Al₂O₃ spinel. When the oxygen partial pressure by C-O₂ consumed oxygen reaction decreases, MgO becomes unstable and decomposes into Mg(g) and O₂; Mg(g) diffuses and transfers along pores or gaps in the materials, reacting with rich-Al₂O₃ spinel to generate new rich-Al₂O₃ spinel and Al(g), Al(g) is nitrided as AlN and then AlN dissolves into rich-Al₂O₃ spinel to form MgAlON. Al(g) and Al₂O(g) diffuse and transfer along pores or gaps in the materials after introduction of Al into Al₂O₃-MgO refractory. Al(g) and Al₂O(g) change into AlN and further dissolve into rich-Al₂O₃ spinel, enhancing N content of MgAlON. Also, in the gas-gas reaction system, Al(g)/Al₂O(g), Mg(g), N₂ and O₂ react with each other to form flake MgAlON.

A series of lightweight ladle working lining castables were prepared with tabular alumina, microporous corundum, and calcium hexaaluminate (CA₆) as aggregates, respectively, reactive α-Al₂O₃ ultrafine powder, SiO₂ ultrafine powder, tabular alumina powder, and fused magnesia powder as matrices, calcium aluminate cement as a binder, and MgO ultrafine powder (D₅₀=5.4 μm), Al(OH)₃ ultrafine powder (D₅₀=8.2 μm) as additives. The influence of aggregate and ultrafine powder on the physical properties, pore size distribution, thermal conductivity, thermal shock resistance, and slag resistance of lightweight refractory castables was investigated. The results show that calcium hexaaluminate (CA₆) can make the castable lightweight, but increase the pore size and reduce the strength and slag resistance of castable. Using microporous corundum can reduce the bulk density of castble, and increase the proportion of micropores, which is beneficial to reducing the thermal conductivity, and improving the thermal shock resistance and slag resistance of castble. When MgO ultrafine powder and Al(OH)₃ ultrafine powder are used as additives, the fluidity and strength of castable can be improved, the ratio of micropores in the castble can be increased, and the fracture energy, thermal shock resistance and slag resistance can be improved.

Slag, fly ash and silica fume were used as reactive aluminosilicate materials to prepare high-strength geopolymer. The influence of silica fume on the setting and hardening of geopolymer was particularly investigated based on the optimization of solid raw materials and activator compositions by a simplex centroid design method. The results show that silica fume can be used as a filler in the packing void between slag and fly ash particles, thus increasing the liquid film thickness due to the release of activator from the voids. This reduces the thixotropy of the paste as well as yield stress and plastic viscosity, thereby improving the flowability of geopolymer. A rapid dissolution of silica fume in a highly-alkaline activator increases the concentration of silicates and decreases alkalinity, leading to deceleration of the reactions of slag and fly ash and the formation of C-A-S-H gels with the prolongation of setting, the retardation of acceleration period, and the decrease of peak reaction heat rate and cumulative reaction heat. This affects the early reaction products and compressive strength development of geopolymer. The compressive strength of the resultant geopolymer reaches higher than 100 MPa with a good workability and reasonable setting time when slag content is more than 50%, fly ash is less than 30% and silica fume is less than 30%, indicating a possibility of producing geopolymer-based UHPC.

The development behavior of shrinkage restraint stress on ultra-high performance concrete (UHPC) surface of steel bridge deck was investigated by theoretical method and restrained shrinkage experiment. The results show that steel bridge deck plays a leading role in restraining shrinkage deformation of UHPC and its restrained degree reaches to 0.41. An exponential growth trend occurs for reinforcement ratio regarding the restrained degree. Also, the restrained degree is linearly correlated to the generated stress in UHPC. The increment of the generated stress induced by reinforcement decreases as reinforcement ratio increases. In addition, a shrinkage value below 300×10^-6 and feature of strain harideing for UHPC applying on bridge deck surface for cracking control were also proposed. A dense reinforcement (≥3%) can have a greater cracking risk in UHPC and equivalent stiffness in structure.

In order to reduce or compensate the autogenous shrinkage of ultra-high performance concrete (UHPC), effects of expansive agent, super-absorbent polymer (SAP), expansive agent (EA) and SAP on the slump flow, setting time, strength and autogenous shrinkage of UHPC were investigated. The results show that EA can reduce the slump flow and shorten the setting time of UHPC, the addition of SAP increases the slump flow and the setting time of UHPC with EA. The EA addition of 4% can slightly increase the compressive and flexural strength of UHPC, the EA addition of 8% can decrease the compressive and flexural strength of UHPC, and the addition of SAP increases the compressive and flexural strength of UHPC with the EA addition of 8%. The autogenous shrinkage of UHPC is reduced by 34.4% at the EA addition of 4%, and the autogenous shrinkage of UHPC is compensated completely with a volume instability at the EA addition of 8%. The SAP addition can further reduce the autogenous shrinkage of UHPC at the EA addition of 4% and increase the volume stability of UHPC at the EA addition of 8%. It is thus indicated that the combined addition of EA and SAP could be an ideal approach to reduce the autogenous shrinkage of UHPC.

To improve the workability of ultra-high performance concrete (UHPC), the effect of superplasticizers (i.e., carboxylic-superplasticizer and phosphonic-superplasticsizer) on the rheological properties of cement/silica fume pastes with a low water-binder ratio was investigated, and the adsorption behavior of the superplasticizers in paste, the packing density and the viscosity of interstitial solution were analyzed. The results show that the superplasticizers have a preferential adsorption behavior on different particle surfaces, and carboxylic-superplasticizer has a superior adsorption ability on cement particle surfaces, and phosphonic-superplasticsizer has a stronger adsorption ability on silica fume particle surfaces. It is indicated that for a cement paste with the similar flow spread, a lower viscosity of the interstitial solutions is the main reason for a lower viscosity of paste with carboxylic-superplasticizer rather than that with phosphonic-superplasticsizer. However, the well- dispersion of silica fume particles with phosphonic-superplasticizer can result in an increased packing density, thus leading to a lower viscosity of cement-silica paste, compared to that of paste with carboxylic-superplasticizer.

A rehydration test of ultra-high performance concrete (UHPC) matrix was conducted to measure the chemically bound water contents, specimen expansion ratios, and compressive strengths of hardened cement pastes at different rehydration time, and the rehydration model was proposed based on the Krstulović-Dabić hydration dynamics of cement and microstructure information of cement hydration. The mechanism regarding the rehydration effect on the water stability was discussed, and the microscopic appearance change with pore structure change was analyzed based on the proposed model. The results show that the bound water content of rehydration increases during the early period but decreases during the late period as the water-cement ratio decreases from 0.30 to 0.15. The specimen expansion ratio increases as the water-cement ratio decreases during the rehydration process. The compressive strength of hardened cement pastes at different water-cement ratios has an alternating tendency of increasing and decreasing with the increase of rehydration time. The simulated data by the model are in good agreement with the experimental results, indicating that the proposed model can accurately simulate the rehydration process of UHPC matrix. The increased scope of compressive strength of hardened cement paste with the water-cement ratio of 0.30 is greater due to its higher hydration rate of cement. During the early period of rehydration, a hydration rate of cement becomes greater, and the rehydration products gradually fill in the initial pores of hardened cement paste. However, during the late period of rehydration, a hydration rate of cement is lower, and the rehydration products cause some microcracks of hardened cement paste due to its volume expansion, resulting in the degradation of properties of UHPC matrix.