Fly ash is produced by coal-fired electric and steam generating plants. Typically, coal is pulverized and blown with air into the boiler's combustion chamber where it immediately ignites, generating heat and producing a molten mineral residue.

While each fly ash brick costs around Rs 3.50-4, a clay brick of the same size costs around Rs 5-5.50 per bricks.

The mixing proportion is generally 40-50% Fly Ash, 50-40% Sand 10% lime and 4% water. Fly ash reacts with lime in the presence of moisture to form calcium silicate hydrate which is the binder material. The raw mix is molded in the machine, pressed under a pressure into bricks.

Fly ash brick making machine is used to toughen the bricks. Since the concentration of calcium oxide is very high in Fly ash Bricks, the brick is described as self cementing.