Abstract

Both agriculture wastes, black rice husk ash (BRHA) and bagasse ash (BA), were used as sand replacement to prepare autoclaved aerated concrete (AAC) product at various temperatures and times. The compressive strengths of AAC were increased with the further autoclaving temperatures and times, except dry density. BRHA and BA have influence on the mechanical properties of AAC with low dry density for all conditions, approximately 6–54%, due to the high Na<inf>2</inf>O and K<inf>2</inf>O content and the fineness of both ashes compared to sand. The appearance of relative high Al<inf>2</inf>O<inf>3</inf> of BA compared to BRHA leads to the additional strength gain of AAC sample containing BA, because of the formation of tobermorite through katoite. Therefore, both residues are shown to be highly potential substitution materials for sand in AAC production.