Understanding the thermomechanical behavior of geopolymer foams: Influence of rate and type of foaming agent and stabilizer

This study assesses the impact of foaming agent type/content (hydrogen peroxide and Zn powder) and stabilizer content on the mechanical, thermal and microstructural of the elaborated geopolymer foams. Eighteen geopolymer foams were synthesized and their microstructure, density, porosity and compressive strength were analyzed before and after exposure to high temperatures (300 and 600 °C). To characterize the raw materials and the samples, several techniques were used, including X-ray fluorescence, X-ray diffraction, Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopy (²⁹Si and ²⁷Al MAS NMR), scanning electron microscopy (SEM), and porosity measurements. Thermogravimetric analysis was also performed to assess the thermal stability of the geopolymer foams with different foaming agent content and type. According to the results, the geopolymer foam with Zn powder as a foaming agent was more stable after exposure to the high temperature. The porosity increased after exposure to 300 °C, meanwhile decreasing after annealing at 600 °C.