Improving physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete by accelerated carbonation

Abstract

This study presents an autoclaved aerated concrete (AAC) with steel slag (SS) as carbonate-able binder. The traditional autoclaving process was augmented with a carbonation stage to improve the physical properties, microstructure and actual carbon sequestration of steel slag based autoclaved aerated concrete (SS-AAC). The macroscopic and microscopic test results showed that the carbonation process stimulated the reactivity of SS to generate gel products, allowing the additional formation of tobermorite during the autoclaving process. Under the synergistic positive effect of the densification-induced micro-pore refinement caused by calcium carbonate precipitation and the excellent gas permeability of AAC, the intervention of carbonation process resulted in SS-AAC with higher compressive strength, more homogeneous carbonation, and more outstanding actual CO2 absorption efficiency. The research provides a potential method for preparing high-volume solid waste AAC with large-scale CO2 utilization to encourage the concrete sector to adopt a sustainable stance.