Factors affecting the property of open-cell fly ash-based porous geopolymer via replica method

Fly ash (FA) is a silicate solid waste produced by coal-fired power plants, which encroaches on land and pollutes the soil. Aluminosilicate can be hydrated using alkali activators to form a high-strength geopolymer. Using organic foam impregnation, geopolymer slurry can be converted into lightweight, high-strength and porous geopolymer. Herein, FA and a sodium-based alkaline activator were mixed to prepare a geopolymer slurry. Immersing a polyurethane sponge in the slurry and adjusting the roller spacing yielded a porous geopolymer with a uniform structure. Different process parameters were adjusted, revealing that the modulus of the alkali activator at 1.5% and 10% water content resulted in a high-strength FA geopolymer. When the dispersant dosage was set at 1%, the slurry had an excellent slurry-hanging effect. Adjusting the roller spacing produced a porous geopolymer with a porosity of 71%, a thermal conductivity of 0.1454 (W/m)/K and a strength of 1.33 MPa. This study highlights the potential for repurposing FA into environmentally friendly and versatile geopolymer materials.