Application of Sporosarcina pasteurii for the biomineralization of calcite in the treatment of waste concrete fines

In this study, we explored and described various parameters of microbially induced calcite precipitation (MICP) using the alkaliphilic bacterium Sporosarcina pasteurii DSM 33, which exhibits ureolytic activity, to stabilize and strengthen waste concrete fines (WCF). Bacterial cell concentration, single and repeated addition of bacterial suspension, and pH adjustment were tested in stage 1 of the experimental agenda in order to tune parameters for sample preparation in stage 2 focused on the effect of MICP treatment duration (14, 30, 60, and 90 days). Two types of WCF materials differing in their physicochemical properties were used for the stabilization. The results of the EDS and XRD analyses confirmed the presence of CaCO₃ crystals, which increased by about 10-12% over time, affecting the porosity, compactness, and strength of the formed composites. The XRD results also indicated that the WCF properties significantly influence the formation of the type of CaCO₃ crystals, supported also by microscopy observations. This study highlights the potential of MICP technology to make concrete recycling more sustainable, aligning with the concept of a circular economy; however, the interplay between the WCF materials of various properties and bacterial activity must be further scrutinized.