Comprehensive review of the properties of fly ash-based geopolymer with additive of nano-SiO2

Abstract

Abstract Nano-SiO2 is a non-toxic, tasteless, and pollution-free material with hydroxyl groups that facilitate the adsorption of water on its surface. Nano-SiO2 is characterized by small particle size, high purity, low density, large surface area, and good dispersion properties. In addition, nano-SiO2 has excellent stability, reinforcement, thixotropy, and optical and mechanical properties. The additive of nano-SiO2 can enhance the mechanical properties and microstructure of concrete. Therefore, nano-SiO2 is widely used as an additive in the field of building materials. Geopolymers have excellent mechanical properties, acid–alkali resistance, fire resistance, and high-temperature resistance. In addition, mineral waste and construction waste can be used as raw materials for geopolymers. Therefore, geopolymers have the potential to substitute ordinary Portland cement and have good prospects for application as construction materials. The application of nanomaterials in geopolymer products has shown that nano-SiO2 is effective in increasing the rate of geopolymerization reaction and reducing the setting time of geopolymers in a controlled quantity. Related results indicate that an appropriate quantity of nano-SiO2 can make the microstructure of fly ash-based geopolymers denser and produce higher mechanical strength. In this study, based on the mechanism of geopolymerization, the effects of nano-SiO2 on the properties of fly ash-based geopolymers including compressive strength, microstructure, hardening properties, shear bond strength, durability, and practical applications have been summarized. This study can provide a basis for understanding the effects of nano-SiO2 on the mechanical properties and durability of fly ash-based geopolymers.