Characterization of Synthetic Foaming Agent with Additives for Lightweight Aggregate Foam Concrete Applications

Lightweight aggregate foam concrete (LAFC) is an improved version of conventional foam concrete (CFC). However, its structural application remains underexplored due to challenges in foam stability and mix design. This study presents a novel method for stabilizing synthetic sodium lauryl sulphate-based foam using the composite additives of xanthan gum (XG) and sodium hydroxide (NaOH). Unlike traditional stabilizers, the combined use of XG and NaOH improved both surface tension and viscosity. It reduced the surface tension by 17% and increased viscosity by 63%, which resulted in a drainage rate of just 2.3% at the 30th min. In comparison, natural and synthetic agents with or without additives have shown drainage rates ranging from 12%–91% and 37%–98%, respectively, highlighting the superior performance of the foam with composite additives. Furthermore, LAFC mixes with sintered fly ash porous aggregates (SFA) are optimized to target densities of 1,400 and 1,800 kg/m3 using 0.2% and 0.3% superplasticizer, respectively. Air void sizes ranged from 138 to 1,500 μm, and area analysis showed a strong correlation with foam volume. Void content was found to be 32.5% and 12.85% for 30% and 10% foam additions, respectively. The resulting compressive strengths are 15 and 30 MPa, with water absorption of 14% and 6%, respectively, meeting ASTM standards. This integrated additive-foam-aggregate strategy offers a scalable pathway for structurally viable LAFC.