Synthesis and characterization of geopolymeric refractory bricks using blends of indigenous fly ash and metakaolin

Abstract

High sintering temperature, is required for the production of refractory bricks which is an energy-intensive operation and utilizes expensive raw material. Geopolymerization is a chemical process that produces a class of inorganic binders of geopolymers. This technique is an energy efficient technique for the geopolymer refractory bricks (GPRB) synthesis because it utilizes low sintering temperature and uses raw material such as fly ash (FA) and metakaolin (MK) which is more economical as compared to conventional raw materials for refractory bricks. As the FA has a high thermal resistance and is available as abundant waste while the metakaoline possesses high compressive strength compared to the FA. In the current study, GPRB were prepared through geopolymerization by blending FA and metakaolin in different weight percents. The six samples have been designed and prepared with various compositions of FA and metakaoline. The compressive strength and thermal conductivity for pure metakaoline based GPRB were 24.15 MPa and 0.78 W/mK, respectively at 28 days, while these were 3.06 MPa and 0.54 W/mK for pure FA based at room temperature. By increasing the amount of FA in the samples increases the thermal resistance, however it reduces the compressive strength of the samples. The optimum blending ratio can be selected for different applications according to the minimum mechanical strength requirements with the desired thermal resistance considering the synthesis of specific refractory.