Porous Geopolymers as Advanced Ecological Materials

Abstract

Porous geopolymers are lightweight materials based on alkali-activated aluminosilicates. When their total porosity is higher than 70 %, they are called geopolymer foams. In this review article, we describe methods used to introduce porosity into geopolymer structure, such as the use of lightening fillers and foaming agents, gelcasting or replica technique. We also present the composition and properties of the prepared materials. Effects on the porosity and its stability are discussed also with regard to our own practical experience. The significance of porous geopolymers is based on their low thermal conductivity, high thermal resistance and non-flammability, as well as on their environmental aspect. When these properties are combined with optimal mechanical strength, the porous geopolymer may represent an alternative to foamed glass, fireproof calcium silicate materials, porous ceramics or aeroconcrete. Applications of porous geopolymers as catalyst support matrices, materials for acoustic absorption or ion exchangers are also studied.