Selecting bacteria for in-depth self-healing of concrete at both room and low temperature

The large-scale application of microbial self-healing techniques of concrete faces serious challenges from low temperature in high-cold regions and oxygen availability in the cracks. In this study, we focus on the temperature sensitivity and oxygen dependence of microbial self-healing techniques of concrete and select bacteria from the cold-resistant facultative anaerobes through microbial growth, mineralization and healing tests with the most frequently used Sporosarcina pasteurii as control group. The results show the cold-resistant bacteria, Brevibacterium frigoritolerans A779 and A793 have the capability of growing at low temperature compared with S. pasteurii fwzy14. S. pasteurii fwzy14 has the best capability of inducing calcite precipitation at room temperature but its precipitation rate decreases dramatically at low temperature; B. frigoritolerans A779 has the approximate capability with S. pasteurii fwzy14 at low temperature with urea and calcium nitrate as calcium carbonate precursor, which makes it a potential candidate for the in-depth self-healing of concrete in a broad temperature range. Consistent with the results of bacterial growth and mineralization tests, bacterial healing tests show that cold-resistant B. frigoritolerans A779 can not only heal the outer part of the cracks but also heal the inner part better than S. pasteurii fwzy14 at low temperature. Therefore, a plan containing both S. pasteurii fwzy14 and B. frigoritolerans A779 is proposed for in-depth self-healing of concrete at both room and low temperature.