In recent years, the addition of nanometer materials to concrete materials has attracted a group of increasing number of scholars’ research interests, and nano-SiO2 is one of the research hotspots. In this paper, we briefly introduce the influence of nano-SiO2 on setting time, slump, shrinkage, durability and mechanical properties of concrete. In addition, this review also includes the microstructure measured by scanning electron microscope (SEM) and the content of various hydration products obtained by X-ray diffraction (XRD). The result shows that the setting time of nano-SiO2 concrete is shortened, the slump is reduced and the shrinkage is improved owing to the high activity and nucleation of nano-SiO2. The improvement effect of nano-SiO2 on concrete is remarkable, especially in the aspect of enhancing the durability of concrete. It should be noted that nano-SiO2 shows limited improvement in the mechanical properties of concrete. In the end, this literature summary explains the macro performance of nano-silica modified concrete through microstructure.

This study presents the key mechanical and residual properties after high-temperature of different Nano SiO2 carbon fiber-reinforced concrete (NSCFRC) mixtures. A total of seven NSCFRC mixtures incorporating 0%–0.35% of carbon fiber by volume of concrete and 0%–2% Nano SiO2 by weight of the binder were studied. The key mechanical properties such as compressive strength, tensile strength, and flexural strength of NSCFRC with 0.25% carbon fiber and 1% NS were 6.8%, 20.3%, and 11.7% higher than PC (0% CFs, 0% NS), respectively. Scanning Electron Microscopy (SEM) shows that Nano SiO2 reduced the internal porosity and increased the compactness of the concrete matrix. Furthermore, the experimental result demonstrates that NSCFRC can improve the mechanical properties of concrete after high-temperature and equations were obtained to describe the evolution of residual properties at elevated temperatures. Results suggested that the effect of carbon fibers on the residual properties of concrete after high-temperature is less than steel fiber and polypropylene fiber. It was also indicated that adding appropriate Nano SiO2 to concrete is an effective means to improve the residual performance after high-temperature.

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