The Micro Analysis and Influence of Nano SiO2 on High-Temperature Compressive Performance of Steel Fiber Reinforced Concrete (SFRC)

This paper investigated the compressive strength of the normal concrete (NC), the steel fiber reinforced concrete (SFRC), the Nano normal concret (NNC) and the Nano-steel fiber reinforced concrete (NSFC) at the high temperature. On the other hand, Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) were used to analyse Micro-Structure and Matrix phase structure at different temperatures. Results presented that the peak values of compressive strength of four types of concrete under high temperature appeared under 200°C.The compressive strength of NSFC was 77.45 Mpa under 200°C, respectively being 1.13, 1.21 and 1.34 times of those of SFRC, NNC and NC. Nano SiO2 could go through secondary hydration reaction with cement hydration product Ca(OH)2 so as to reduce Ca(OH)2 content and refine Ca(OH)2 crystals, transform Ca(OH)2 having adverse effect on strength into C-S-H gels and improve structural compactness. Therefore, addition of nano SiO2 could obviously improve high-temperature compressive strengths of the concrete, and it especially played a significantly role in improving compressive strength of SFRC.