Thermomechanical performance of blended metakaolin-GGBS alkali-activated foam concrete

Abstract

This study aims to synthesize, at ambient temperature, blended metakaolin-ground granulated blast furnace slag (MK-GGBS) foam concrete (FC) presenting acceptable thermomechanical performance for use as self-bearing insulation material. First, a binder composition that could be used for MK-GGBS FC production was identified. Fourteen paste formulations were produced and analysed to determine the best proportions of MK, GGBS and activator to be used in an alkali-activated material (AAM) FC matrix. Certain requirements were specified for the fresh paste (initial setting time >180min) and solid materials (high compressive strength and moderate shrinkage) to be used for FC production. The optimized mix was then employed for AAM FC production by using an H2O2 blowing agent (gas-foaming method). The influence of two main parameters (H2O2 and surfactant contents) on AAM FC properties (density, porous structure, thermal conductivity and compressive strength) were investigated. FC density mostly depends on H2O2 content. The FC porous structure depends strongly on both H2O2 and surfactant contents. High surfactant content FCs have a thin homogenous porous structure. At constant density, FC compressive strength depends on the surfactant content. An optimized surfactant content maximizing FC compressive strength at constant density was identified.