Fabrication, sinterabilty and characterization of non-colored and colored geopolymers with improved properties

Non-colored and colored geopolymers were prepared from high-grade Egyptian kaolin. 10 wt% of chemically synthesized nano nickel aluminate was used as colorizing agent for geopolymer. The dried non-colored geopolymer was sintered at 800 °C–1200 °C. Bulk density and apparent porosity were determined by water displacement method. Linear shrinkage was also calculated. Phase composition, microstructure, thermal behavior and structure elucidation were examined by x-ray diffraction, scanning electron microscope, thermal gravimetric analysis and Fourier transform infrared, respectively. The compressive strength was also determined. The results revealed that the fabricated geoplymers exhibited interested physical and mechanical properties with a developed microstructure. The dried-colored geopolymer showed improved properties greater than the dried non-colored one due to the development of microstructure and formation of additional phases. For sintered non-colored geopolymer, the properties were improved with increasing sintering temperature up to 1000 °C, then deteriorated after sintering at 1200 °C due to the overheating with formation of liquid phases and foamed structures.