Impact of portland cement type on bacterial viability in biological concrete

Abstract

Biological concrete combines the advantages of traditional concrete and autonomous crack repair. As the self-healing ability of biological concrete is ensured by bacteria-induced calcium carbonate precipitation, long-term bacterial viability becomes critical. Unfortunately, the viability of bacteria tends to drop drastically within the first several days after their incorporation into biological concrete, complicating the healing process. Bacterial mortality is most often related to either the high pH values of early age concrete or mechanical stress during the mixing and hardening of the concrete. In this paper, we report a detailed analysis of the influence of cement type on bacterial viability. We reveal that a particular cement type used for concrete production is of paramount importance to bacterial viability as it directly correlates with the chemical composition of concrete and, subsequently, the environment that bacteria thrive in. We demonstrate that specific metal oxides present as impurities in cement, namely CuO and ZnO, act as bactericidal agents. To achieve the best healing effect, we suggest that the chemical composition of a given cement type is analyzed, and the inhibitory activity of each detected compound on bacteria is studied before the production of biological concrete.