Synthesis of mesoporous geopolymers containing zeolite phases by a hydrothermal treatment

The present study investigates the synthesis of mesoporous geopolymers containing different nano-crystalline zeolite phases. A hydrothermal treatment procedure was utilized to synthesize the mesoporous geopolymers using fly ash, slag and alkaline solution. The effects of slag addition and molar ratio of alkaline solution on the microstructure and mechanical strength of the geopolymers were investigated and evidenced by XRD analysis, compressive strength and nitrogen adsorption tests. The test results showed that the geopolymers incorporating fly ash and slag consisted of Na-P1 and Sodalite zeolite phases, and had the characteristic of mesoporous materials (2 nm < pore size < 50 nm) in which capillary condensation may occur. The highest compressive strength of the geopolymers was 16.57 MPa, and the desired mesoporous characteristics were met by adding 20% slag content to fly ash and adopting the hydrothermal process at a relatively low temperature. The highest BET surface area and single point adsorption pore volume of the mesoporous geopolymers were 114.16 m²/g and 0.2677 cm³/g, respectively.