Physical and high temperature properties of basalt fiber-reinforced geopolymer foam with hollow microspheres

Abstract

For ultra-light geopolymer foam, it is challenging to maintain excellent mechanical properties and foaming stability while continuously reducing the density. In this study, basalt fibers (BF) and hollow microspheres (HM) were used to prepare a basalt fiber-reinforced metakaolin (MK)-based geopolymer foam (FRGF) and the workability, microstructure, physical properties, high-temperature performance, and shrinkage characteristics were systematically investigated. Results indicate that incorporating 50% HM into FRGF significantly reduces the fluidity by 31.2% and reaction rate of the geopolymer paste, slows down the decomposition rate of hydrogen peroxide, and enhances the stability of the foaming process. Additionally, the incorporation of HM increases the total porosity of the FRGF from 75.4% to 86.3%, lowers the bulk density from 0.42 g/cm3 to 0.34 g/cm3, and decreases the thermal conductivity to 0.0681 W/(m⋅K). Concurrently, the introduction of BF significantly enhances the mechanical properties of FRGF, with a 28-day compressive strength reaching 2.49 MPa. After treatment at 1000 ℃, the FRGF transformed from an amorphous gel structure to a crystalline structure. The sintering between BF and the matrix notably enhances the performance of interfacial transition zone (ITZ), further increasing the energy absorption capability and decreasing the linear shrinkage of FRGF at high temperatures (1000 °C) by 55.2%. In conclusion, 50% HM and 0.6% BF demonstrated superior mechanical properties, thermal insulation, and high-temperature performance. It offers a strategy to resolve the contradiction between the density, mechanical performance, and stability of geopolymer foams and has potential applications in the field of high-temperature insulation.