Q1: For making fly-ash building bricks, the following mix of fly-ash, sand and lime, is

ANS:A - 80 : 13 : 7

The raw materials for Fly Ash Bricks are:

Material ------ Mass
Fly ash ------ 60%
Sand/Stone dust ------ 30%
Ordinary Portland Cement/(Lime+Gypsum) ------10%
Total formula of material ------100%

The strength of fly ash brick manufactured with the above compositions is normally of the order of 7.5 N/mm2 to 10 N/mm2.

Fly ash bricks are lighter and stronger than clay bricks.