Comprehensive review of the properties of fly ash-based geopolymer with additive of nano-SiO ₂

Abstract

Abstract Nano-SiO 2 is a non-toxic, tasteless, and pollution-free material with hydroxyl groups that facilitate the adsorption of water on its surface. Nano-SiO 2 is characterized by small particle size, high purity, low density, large surface area, and good dispersion properties. In addition, nano-SiO 2 has excellent stability, reinforcement, thixotropy, and optical and mechanical properties. The additive of nano-SiO 2 can enhance the mechanical properties and microstructure of concrete. Therefore, nano-SiO 2 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-SiO 2 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-SiO 2 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-SiO 2 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-SiO 2 on the mechanical properties and durability of fly ash-based geopolymers.