Effects of red mud on workability and mechanical properties of autoclaved aerated concrete (AAC)

Red mud poses a severe threat to the local environment that needs to be disposed of properly. This study investigated the feasibility of using red mud in autoclave aerated concrete (AAC), whose performances were systematically assessed, and the performances were further interpreted by microstructural analyses. The initial results reveal the negative impacts of using red mud in AAC concerning workability and strength, which could be assigned to the low activity of red mud as well as its small particle size, and the process of gas generation inside AAC was inhibited. In ad-dition, the worse pore structure and the excessive content of tobermorite in AAC with a higher amount of red mud could also account for its reduced strength. Further, 22.5% of red mud to re-place fly ash in AAC could be the optimal ratio considering several indexes of AAC involving red mud, and the use of polycarboxylic acid in AAC or adjusting the water-solid ratio of AAC can greatly improve the overall performance of AAC with red mud, which satisfies the requirements stipulated by the standard.

Automated summary

Red mud poses a severe threat to the environment and needs to be properly disposed of. When using red mud in autoclave aerated concrete (AAC), its low activity and small particle size negatively impact the workability and strength of AAC. Additionally, a higher amount of red mud results in worse pore structure and excessive content of tobermorite, leading to reduced strength. The optimal ratio of red mud to replace fly ash in AAC is 22.5%, and the overall performance of AAC with red mud can be greatly improved by using polycarboxylic acid or adjusting the water-solid ratio, meeting the standard requirements.