Effect of triethanolamine on the properties and hydration of fly ash-based geopolymer foam

Low compressive strength of fly ash-based geopolymer foam (FGF) severely limits its application in areas such as building thermal insulation, partition walls, and foundation backfill. In this study, triethanolamine (TEA) was examined as an additive with dual functions: acting as a foam stabilizer in the foam solution and enhancing the strength of FGF samples. The effects of TEA on the stability of preformed foam and the workability, bulk density, and compressive strength of FGF samples at room temperature were evaluated. The hydration products were examined by XRD, TGA, FTIR and SEM, and the pore structure was evaluated by image analysis method. Results showed that TEA was effective in enhancing stability of preformed foam. When 0.70 wt% of TEA was incorporated into foam solution, the drainage half-life of preformed foam increased by 50.5 % to 45.3 min. FGF samples prepared with TEA-modified preformed foam exhibited good workability and bulk density of 660 ± 20 kg/m³. The 3-day and 28-day compressive strengths of the FGF sample added with 0.70 wt% TEA increased by 50.0 % and 30.7 % to 1.17 MPa and 3.32 MPa, respectively. The enhancement was attributed to the effects of TEA on facilitating the hydration of geopolymer matrix and optimizing the pore structure of the FGF system.