Lightweight and durable foamed geopolymers aerated using dual-function lime and aluminum powder for sustainable construction

Abstract

This study examines the production of lightweight foamed geopolymers using aluminum powder as the main foaming agent and lime as both a partial replacement for ground granulated blast-furnace slag (GGBFS) and a secondary contributor to pore formation. While the individual effects of aluminum powder and lime have been reported in the literature, their combined use in GGBFS-based foamed geopolymers has received little attention. In particular, the influence of lime on both matrix development and pore generation remains unclear. Nine mixtures were prepared by varying the lime content between 0 and 20% and the aluminum powder dosage between 3 and 12 g. The results indicate that adding 10% lime produced the most balanced performance. At this level, the pore structure became more uniform, pore coalescence was reduced, and early-age strength improved compared with mixtures without lime. Increasing the lime content to 20% did not generate additional porosity and generally resulted in lower performance. The beneficial effect of 10% lime was also reflected in the durability results. Mixtures containing 10% lime together with moderate aluminum dosages showed lower thermal conductivity and better resistance to freeze–thaw cycles and carbonation. SEM observations confirmed that these mixtures developed a more homogeneous pore network with fewer interconnected voids. The findings suggest that lime can do more than simply replace part of the precursor. When used at an appropriate dosage, it alters the foaming process and helps stabilize the resulting pore structure. This offers a practical route for producing foamed geopolymers with improved mechanical performance, durability, and thermal efficiency.