Feasibility of incorporating autoclaved aerated concrete waste for cement replacement in sustainable building materials

Abstract

Autoclaved aerated concrete waste (AACW) is a common low-strength cement-based construction and demolition waste, which is currently disposed by landfills and hard to be directly used as supplementary cementitious material. The present work proposed a potential approach incorporating AACW for cement substitution in sustainable building materials. Wet-milling technique was used to dispose and improve the fineness of AACW (median particle size, as low as 2.3 μm). It was proved that AACW is suitable for wet-milling treatment due to its porous texture and low-strength. The pH value and electrical conductivity of the AACW slurry was notably improved. Water requirement was increased by the ultrafine AACW. Both setting time and the main hydration heat location were obviously brought forward by ultrafine AACW, indicating its early hydration acceleration. Compressive strength of ultrafine AACW replaced cement pastes present higher or equivalent value compared with pure cement paste, within 30% replacement level. Pore structure was effectively refined by the ultrafine wet-milling AACW. It was proved that AACW could be efficiently used as an alternative cementitious material in cement and concrete after wet-milling treatment, thus bring environmental and economic benefits.