Regulating the chemical foaming and pore distribution in aerated geopolymer concrete

This study investigates a method to regulate the foaming effect, enhance foam stability and overall performance of chemically foamed aerated geopolymer concrete (AGC) using recycled waste latex paint (RWP). The RWP consists of acrylic polymers and surfactants which are expected to regulate the foaming effect in AGC. AGC was synthesised by alkali activation of fly ash and slag, with Aluminium powder as the chemical foaming agent. A varying level of RWP was introduced as the foam regulating agent to enhance the rheological properties and gas bubble distribution in the AGC matrix. The systematic experimental analysis revealed that higher RWP dosage increased the expansion height by 75 % with a well-regulated expansion behaviour, attributed to the presence of soluble polymers and surfactants in RWP that mitigate bubble collapse and enhance the chemical foam stability. Additionally, increased RWP dosage improved the viscosity and yield strength of AGC mixes, facilitating better gas bubble migration in the matrix, resulting in finer and uniform pore structure. High RWP content increased porosity by 31 % and reduced density by 35 %, indicating its efficiency in producing lightweight AGC products. Although a reduction in the compressive strength of about 40 %–75 % was observed due to increased pore connectivity and reduced geopolymerisation from pigments and impurities in RWP, microstructural analysis confirmed reduced bubble coalescence and pore irregularity. Enhanced interfacial paste strength resulted in a finer and more uniform pore distribution. These findings demonstrate the potential of RWP as a value-added, sustainable additive for producing lightweight, non-load bearing AGC products with enhanced thermal and acoustic properties, contributing to sustainable construction and promoting the circular economy of waste paint products. • Foam expansion regulated with recycled paint in aerated geopolymer concrete. • Recycled paint improves foam stability and mitigates bubble collapse. • Density reduced from 1100 kg/m 3 to 725 kg/m 3 with recycled paint additive. • Microstructure shows improved pore distribution and reduced irregularity with paint.