Changing the soaking method of microbially induced calcium carbonate precipitation technology to improve the reinforcement effect of recycled concrete aggregates

In this study, the effects of the soaking method employed during the concrete reinforcement process on the properties of recycled concrete aggregates (RCAs) with different particle sizes were investigated based on biodeposited calcium carbonate technology. The microstructure and properties of RCAs and the macroscopic properties of recycled aggregate concrete (RAC) before and after the enhancement treatment were studied. The results showed that the presoaked bacterial solution can improve the reinforcement of RCAs, and the best performance of RCAs was obtained after reinforcement by soaking twice (first time, soaking RCAs into nutrient solution after presoaking with the bacterial solution (Method B), the next time soaking RCAs directly into mixed culture solution (Method A)). After immersing twice, the biodeposited calcium carbonate reinforced the defects of RCAs and coated the surface of RCAs. The mechanical properties of RAC were significantly improved owing to the use of the enhanced RCAs, and the RCAs with secondary soaking treatment endowed the concrete with superior mechanical performance. •Systematically investigated the experimental parameters of the biodeposition calcium carbonate process.•The influence of soaking method and soaking frequency on the performance of RCA were investigated.•The changes in microstructure before and after reinforcement of RCAs were described in detail.•The effect of biodeposited calcium carbonate on the surface modification of RCAs were analyzed.•Clarified the enhancement mechanism of the MICP technology.