Insight into the temperature stimulation on the self-healing properties of cement-based materials

The concrete constructions under the complex and variable external loads easily produce structural cracks, severely limiting the service life. Traditional methods for crack repairing such as spraying and chemical grouting, are usually with the high cost and potential environmental problems. In recent years, microbial self-healing has aroused great attention in the crack repair of concrete due to its environmental safety and high self-healing potential. Nevertheless, previous studies have shown that the healing efficiency of microbial cement stones at low temperatures was not ideal. Temperature stimulation seems to be feasible to accelerate the healing process because temperature is one of the critical factors impacting microbial mineralization. To verify the applicability of temperature stimulation to the regulation of microbial healing efficiency, this paper investigated the changes in growth rate, urease activity, cell shape, and mineralization rate of Sporosarcina pasteurii under temperature stimulation at first. And then, the healing properties of cement stones without cracking and cracked cement stones under temperature stimulation were evaluated. The interaction mechanism of temperature stimulation on the healing properties was revealed by establishing the relationship between the microstructure parameters and macro performance. This paper proved that it was capable to improve the healing efficiency of microbial cement stones by temperature stimulation. Besides, the results showed that at 7 -37 degrees C, the growth rate and miner-alization rate of bacteria were improved by raising the culturing temperature. Moreover, we found that tem-perature stimulation impacted the growth and the mineralization of bacteria, thus, influencing the microstructure and healing properties of microbial cement stones. In addition, the healing efficiency was dominated by microbial mineralization rather than cement hydration at 7 -43 degrees C. More importantly, the temperature stimulation on the microbial cement stones with Sporosarcina pasteurii should be limited within 43 degrees C. This paper provides a reference for the research on the improvement of the healing efficiency in microbial cement materials with temperature stimulation.