Influence of Fly Ash on Refractory Properties and Microstructural Characteristics of Sustainable Refractory Bricks

In the present experimental investigation, an attempt has been made to utilize fly ash in different proportions in combination with kaolin clay and fire clay to develop sustainable refractory brick. Six different types of sustainable refractory bricks were cast by combining and replacing kaolin clay and fire clay with 10%, 20%, and 30% of fly ash, respectively, adding 4–6% of water. Semi-dry mixed mortar was hydraulically pressed to make bricks using a friction press machine and burnt in the electric furnace at 950 °C and 1150 °C and in the tunnel kiln furnace at 1350 °C. The bulk density, apparent porosity, and refractory properties viz. cold crushing strength, and linear shrinkage tests were performed on the prepared bricks. The microstructural characteristics have been investigated using X-ray diffraction and field emission scanning electron microscopy analysis. The favorable test features suggest that there is an option to use fly ash up to 20% in the production of moderate heat duty refractory brick. Field emission scanning electron microscopy and X-ray diffraction analysis indicate that usage of fly ash in place of fire clay or kaolin clay up to 20% aids in vitrification, which results in high cold crushing strength.