The ingredients are forced into the mould by the spinning teeth of the distributor. The top mould then descends, while the lower mould vibrates at the same time. In general, the bricks will be completed in 15–40 seconds. The moulding cycle is determined by the block machine models. 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.