Effect of Fine Al-Containing Waste in Autoclaved-Aerated Concrete Incorporating Rice-Husk Ash

Abstract

This investigation is focused on the physical and mechanical properties, as well as the microstructure of autoclaved aerated concrete (AAC) incorporating both rice-husk ash (RHA) and aluminum (Al)–containing waste (AW) as a partial aggregate and expansive agent replacement. Normally, these wastes are disposed of in landfill and have low reactions at room temperature. Thus, the use of these wastes in AAC could reduce waste in the environment as well as reduce autoclaving time or temperature. The fineness of ground AW, analyzed by laser particle-size distribution, were classified as high (AWH), medium (AWM), and low (AWL), with the mean particle sizes of 9.71, 29.91, and 51.11 μm, respectively. The AW was used to substitute metallic aluminum powder at levels of 5, 10, 15, and 20% by weight. Samples with AW substitution gave lower unit weights and compressive strengths than the reference sample, except at 5% of AAC containing medium and low fineness. Scanning electron microscopy (SEM) micrographs reveal that at a higher replacement level and higher fineness of AW, fibrous calcium silicate hydrate (CSH) was formed instead of tobermorite, at 4-h autoclave curing.