This study demonstrates the development of geopolymer foamed concrete (GFC) by introducing a double hierarchical porous structure using premade foam and lightweight porous aggregates. Hydrophobic expanded perlite (EP) was used as porous aggregate and the addition of 10% and 20% of the binder (by eliminating corresponding volumes of sand) were investigated.
It was observed that the incorporation of EP has brought obvious benefits in improving the mechanical and thermal properties of GFC. The amount of foam required to achieve a similar density of GFC was reduced by 19% and 53% for 10% and 20% of EP respectively, due to the presence of the large amount of open pores in EP. The compressive strength of cube specimens has increased by 75% and 180% at 7 days and 65% and 188% at 28 days, respectively. The reaction kinetics of geopolymers studied using FT-IR reveals that the reaction rates of geopolymer binders increase with the amount of EP.
It is also shown that the increase in the amount of geopolymer gel particulates surrounding bubbles is the major reason for attaining fine air voids and strong binding skeleton in GFC-20EP, compared to the other two groups. Consequently, the pore homogeneity index, as measured from the ultrasonic velocity at different directions, was improved from 50% to 90%. The thermal performance tests conducted using prototype test cells reveals that the indoor thermal conditions will significantly improve when the GFC-20EP is used as building elements. This is particularly demonstrated by the reduction in peak indoor temperature of 1.8 °C and an increase in thermal inertia of 1.7 °C with GFC-20EP, compared to GFC-s.