Development of Low-Thermal-Conductivity Fly Ash Geopolymer Foam Mortars with Stabilizer Effects and 3D Printability Assessment (2026-03)¶

This study investigated the potential of fly ash-based geopolymer foam mortar as an eco-friendly insulating material, with a specific focus on the influence of various stabilizing agents. Capitalizing on the aluminosilicate-rich composition of fly ash, the synthesis process employed hydrogen peroxide (H₂O₂) to promote aeration and enhance thermal insulation. To optimize stability and mechanical performance, polyvinyl alcohol (PVA), vegetable oil (VO), and sodium lauryl sulfate (SLS) were used as stabilizers. The resultant composites were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis-derivative thermogravimetry (TGA-DTG), and mercury intrusion porosimetry (MIP). Results indicated that at a constant water-to-binder ratio of 0.40, higher H₂O₂ concentrations enlarged pore dimensions but compromised compressive strength. However, the inclusion of stabilizing agents successfully reduced pore size and improved pore distribution, significantly altering the internal microstructure and bonding mechanisms. Specifically, PVA facilitated the formation of isolated pores, whereas vegetable oil and SLS promoted interconnected pore networks. Thermal conductivity measurements ranged from 0.07 to 0.15 W/m·K, demonstrating a direct correlation between increased porosity and reduced thermal conductivity. Among the additives tested, 1.5% PVA proved the most effective stabilizer, yielding optimal insulation characteristics. Furthermore, this optimized matrix was successfully applied in 3D printing processes to enhance energy efficiency. Collectively, these findings demonstrated the significant potential of fly ash-based geopolymer foam mortar as a viable thermal insulator and provided critical insights into the microstructural interactions and physicochemical properties.