Fly ash brick (FAB) is a building material, specifically masonry units, containing class C fly ash and water. All fly ash includes substantial amounts of silicondioxide (SiO‌2 ) aluminum oxide (Al‌2O‌3 ) and calcium oxide (CaO), the main mineral compunds in coalbearing rock strata. Fly ash can be used as a replacement for some of the Portland cement contentsof concrete.