Autoclaved aerated concrete incorporating waste aluminum dust as foaming agent

Aluminum dust is a waste from aluminum dross recycling industry. Instead of treating aluminum dust to remove or to immobilize aluminum metal for landfill disposal, a novel approach of utilizing aluminum dust as foaming agent in replacement of costly aluminum powder for the synthesis of autoclaved aerated concrete (AAC) is proposed. Results show that 15.6 g of aluminum dust is able to generate the same amount of gas as 1 g of aluminum powder and both have comparable gas generation rate. Inclusion of aluminum dust causes rapid stiffening of fresh paste while the use of aluminum powder does not change the yield stress development of AACs. As a result, volume expansion and density of Al dust-AAC remains almost unchanged with increasing dosage of aluminum dust. Al dust-AACs; however, possess smaller voids due to higher yield stress of paste. The use of aluminum dust as foaming agent may not achieve a very low density AAC, but it does not compromise the mechanical properties of the resulting Al dust-AACs, which possess a density of around 800 kg/m3 and a compressive strength of about 2.5 MPa in this study. Aluminum dust thus can be considered as alternative foaming agent for AAC production.