Valorization of sewage sludge ash into sustainable porous geopolymer: Dual functions as supplementary foaming agent and precursor

Abstract

This study presents a sustainable approach to producing geopolymer foam concrete by incorporating sewage sludge ash (SSA), a porous, aluminosilicate-rich byproduct of sewage sludge incineration. The effects of SSA dosage, alkaline activator modulus, and foam stabilizer content on the physical properties, microstructure, phase composition, carbon footprint, and thermal insulation performance of SSA-enhanced geopolymer foam concrete (SGFC) were systematically investigated. The results indicated that the SGFC exhibited optimal performance with a 30 % SSA dosage, an alkali activator modulus of 1.4, and 2 % foam stabilizer content. Under these conditions, SGFC achieved a significantly improved thermal insulation performance due to its optimized pore structure, with a thermal conductivity of 0.081 W/m·K and an exterior wall energy consumption of 39.0 W/m², while carbon emissions were as low as 136 kg CO₂/m³. These findings underscore the potential of SSA as a reactive and eco-friendly precursor for high-performance, low-carbon construction materials.