Enhancement strategies for recycled brick aggregate concrete using MICP and EICP treatments

Abstract

Utilization of recycled brick aggregate (RBA) in concrete production is limited due to its high porosity, which negatively affects the strength and durability of concrete. This study aims to address these limitations by exploring microbial- and enzyme-induced carbonate precipitation (MICP/EICP) treatments to enhance the RBA properties. The treatment processes were optimized by determining an optimal Ca concentration, and mitigating ammonia release and ammonium residue. The effects of MICP and EICP treatments on the properties of RBA and its resultant concrete were evaluated, and the underlying mechanism was revealed using microscale analysis. The results showed that both MICP and EICP treatments resulted in enhanced properties of RBA and its resultant concrete due to the refinement effect of CaCO3 precipitation (vaterite, calcite, and aragonite for EICP but only vaterite for MICP) on the macro pores of RBA, whilst EICP treatment yielded a greater performance with more proportion of capillary pores and more uniform distribution of precipitation.