Influence mechanism of autoclaved aerated concrete waste on the hydration of blended cement with high-volume slag

This study focused on the effect of recycled waste autoclaved aerated concrete powder (WAP) on blended cement with high-volume slag (slag to cement clinker mass ratio of 3:7), aiming to provide a new approach to the treatment of autoclaved aerated concrete waste (AACW). The working properties, hydration process, hydration products, and microstructure of the blended pastes were studied. The results indicated that the addition of WAP improved the poor early performance of the blended cement with high-volume slag. However, WAP reacted with Ca(OH)₂ (CH) in a pozzolanic reaction, significantly reducing the CH content and thereby lowering the alkalinity of the blended cement. This decrease in alkalinity subsequently hindered the hydration of the slag in the later stages of the process. WAP improved the early compressive strength of blended cement through its effect on cement hydration, and the strength of the paste with 50 % WAP increased by 76.8 % at 3 d compared to the control. However, at 28 d curing age, the compressive strength of the experimental group was lower than that of the control. The moderate amount of WAP had little effect on the compressive strength, which was reduced by 7.6 % for the paste with 20 % WAP compared to the control. Additionally, the inclusion of WAP refined the pore structure of the blended pastes, resulting in fewer harmful pores.