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研究了掺纳米SiO2的钢纤维混凝土(NSFC)、钢纤维混凝土(SFRC)和普通混凝土(NC)三种材料在不同加热温度后的抗压、劈裂和抗折强度等力学性能,对不同温度热处理后的微观结构进行了SEM分析,对钢纤维与过渡区界面的相结构进行了XRD分析。结果表明:在测试温度范围内,NSFC的抗压、劈裂和抗折强度均高于SFRC和NC的强度,且在400℃时达到最大值。在常温下,NSFC的抗压、劈裂和抗折强度较NC分别提高27.01%、63.28%和54.12%,400℃高温热处理后比NC分别高35.09%、84.62%和87.23%;SEM分析表明,在钢纤维与过渡区的界面处,致密度提高,显微硬度提高。由于固相反应,使界面区结构发生变化,在钢纤维表层形成扩散渗透层(白亮层),即化合物层,呈锯齿状,XRD分析证明,白亮层主要由FeSi2和复杂的水化硅酸钙组成,从而增强了钢纤维与基体的粘结力,提高了混凝土的高温力学性能。
The mechanical properties such as compressive strength, splitting and flexural strength of steel fiber reinforced concrete (NSFC), steel fiber reinforced concrete (SFRC) and ordinary concrete (NC) doped with nano-SiO2 were studied. The microstructure after heat treatment was analyzed by SEM. The phase structure of the interface between the steel fiber and the transition zone was analyzed by XRD. The results show that the compressive strength, splitting and flexural strength of NSFC are higher than that of SFRC and NC in the test temperature range and reach the maximum at 400 ℃. Compressive strength, splitting and breaking strength of NSFC increased by 27.01%, 63.28% and 54.12% respectively at room temperature, and were 35.09%, 84.62% and 87.23% higher than that of NC after heat treatment at 400 ℃ respectively. SEM analysis showed that, At the interface of steel fiber and transition zone, the density increases and the microhardness increases. Due to the solid-state reaction, the structure of the interface region was changed. The diffusion-penetrating layer (white-bright layer), ie, the compound layer, was jagged on the surface of the steel fiber. XRD analysis showed that the white-bright layer mainly consisted of FeSi2 and complex hydrated calcium silicate Composition, thereby enhancing the bonding of steel fibers and matrix, improve the high temperature mechanical properties of concrete.