Bottom ash from coal-fired power plants is a potential raw material for the production of ceramic tiles, bricks and
blocks for various applications. In this work we are presenting a novel microwave method to utilize the bottom
ash to produce thermal insulating bricks. Foam samples were prepared by microwave foaming of the mortar
prepared by milling the bottom ash, sodium silicate and NaOH. The microwave foaming ability of different slurry
compositions and the physical and mechanical properties of the foamed samples were evaluated. FTIR analysis
reveals that the degree of geopolymerization increases with increasing fraction of sodium silicate. Foams with
low bulk density, high porosity, low thermal conductivity and compressive strengths were obtained by this
method. With varying the bottom ash to sodium silicate ratio, it is possible to modulate the physical and
mechanical properties of the insulating bricks.