Pore structure profile of ambient temperature-cured geopolymer concrete and its effect on engineering properties

Ambient temperature-cured geopolymer concrete (GPC) with solid alkali activators are attracting attention as an eco-friendly alternative to OPC-based concrete (OPCC) for industrial applications. This research investigates the pore structure and microstructural characteristics of GPC via porosimetry and micrography and strives to connect the micro-scale characteristics to macro-scale engineering properties. The dominance of slag and low water content resulted in a denser and more homogenous microstructure in the binder with fewer microcracks and voids. Furthermore, a refined pore structure was observed when the fly ash/slag ratio was 60/40. The porosimetry analysis demonstrated that OPCC possessed a uniform pore structure with a similar porosity profile throughout the concrete cross-section. GPC showed a descending pore gradation profile from top to bottom. The difference in the pore structure profiles can explain the previously witnessed shrinkage behaviour of GPC and OPCC in restrained conditions.