Preparation and evaluation of geopolymer composites containing alumina particles at ambient temperature and after heating

In this research, geopolymer composites were prepared using metakaolin along with silica fume and potassium hydroxide as alkaline activators and alumina particles. The effect of alumina particle size to achieve castable microstructure and their mechanical properties were investigated. Different Si:Al mole ratio (1.5, 2, 2.5 and 3) and K:Si mole ratio (0.20, 0.25, 0.33) were formulated and the strength was maximized at Si:Al=2.5 and K:Si=0.33. However, its deformation and porous microstructure at high temperatures greatly reduced dimensional stability and strength. Microstructural properties and mechanical strength of samples sintered at 600, and 1000 oC after heating and at environmental conditions were studied and significant changes in the microstructure and strength of samples were observed. Sintering in the presence of the liquid phase caused the pores to collapse, creating a strong bond between the particles and increasing the density at 1000oC.