Fly Ash bricks are made of fly ash, lime, gypsum and sand. The raw materials are blended in desired proportions in a Pan mixer for 4-5 minutes and compressed. They undergo curing for a minimum of 14 days and are then air dried for 7 days. Strength of these bricks can be engineered by varying the compositions.Fly ash bricks are lighter and stronger than clay bricks. Main ingredients include fly ash, water, quicklime or lime sludge, cement, aluminum powder and gypsum.