Regulating the chemical foaming reaction to control the porosity of geopolymer foams

High percentage of aluminium foaming agent is not desirable in geopolymer foams made with aluminium powder. Therefore, the kinetics of aluminium reaction is regulated to increase the porosity of geopolymer foams without increasing the extent of aluminium usage. In geopolymer foams made by Al powder, the geopolymerization reaction and aluminium foaming reaction occur simultaneously. By adjusting the ratio of alkali activators, the high degree of aluminium reaction has been coupled with faster setting of geopolymers, and therefore, the extent of porosity and the pore size distribution has been increased in geopolymer foams without the need to add more Aluminium powder. Aluminium powder has high embodied energy, and this study helps to minimise the negative environmental footprint of geopolymer foams which are aerated by aluminium powder.