In-situ formation of geopolymer foams through addition of silica fume: Preparation and sinterability

Recently, the production of clean binding materials without energy consumption and CO2 emission has paid a great attention. In-situ formation of geopolymer foams through addition of silica-fume waste is the main goal of the present study. Moreover, an attempt to study the effect sintering temperature on the prepared geopolymer foams was also conducted. Through geopolymer formation, the silicon impurity in silica fume reacted with the alkali activator and produced hydrogen gas which entrapped inside the structures generating highly porous foams. Geopolymer foams were prepared by alkali activation of metakaolin with partially replacement by 2.5, 5 and 7.5 mass-% silica fume. To study the effect of temperature or sinterability, the prepared geopolymer foams were sintered at 800, 1000 and 1200 degrees C. Both dried and sintered geopolymers were subjected for assessment by various tools. The physical, microstructural and mechanical properties were investigated. The results revealed that porosity percentage of dried and sintered geopolymers increased with increasing the amount of added silica fume and decreased with increasing sintering temperature. On the other hand, the compressive strength was opposite to the porosity trend. Generally, the best results were for the geopolymer that contains 5% silica fume. The optimum sintering temperature to produce sintered ceramics having good properties was 1000 degrees C.