Use of slaked lime and Portland cement to improve the resistance of MSWI bottom ash-GBFS geopolymer concrete against carbonation

This study investigated the resistance of municipal solid waste incinerator bottom ash geopolymer concrete (BA), Ca(OH)2-modified BA, and Portland cement-modified BA against carbonation using the accelerated carbonation test. The resistance enhancing effects and resistance enhancing mechanism of Ca(OH)2 and Portland cement against carbonation of BA were studied via periodic monitoring of carbonation depth and microscopic analysis of carbonation products. The results show that BA has a decreased resistance against carbonation compared to cement concrete; Ca(OH)2 and Portland cement can both enhance the resistance against BA carbonation. Larger contents will lead to larger enhancements. The enhancing effect of Portland cement on the carbonation resistance of BA exceeds that of Ca(OH)2. The main reason for this is the polymerization of the initial stage of hydration consuming part of the Ca(OH)2, which lowers the effective Ca(OH)2 content.