Performance of biological methods on self-healing and mechanical properties of concrete using S. pasteurii

Biological methods (adding bacteria to the concrete mixtures) among the most recently investigated procedures increase the durability of concrete and repair concrete cracks. In the present study, different biological methods were used to heal the cracks of concrete and the most suitable method was subsequently introduced as the main aim of the research. For this purpose, the culture medium, various sources of calcium salts as bacterial nutrients, and the effect of air-entrained agent on the healing process were studied. The results showed that the use of bacterial nutrient inside the concrete mixes has an affirmative impact on the mechanical properties and self-healing characteristics of concretes. Simultaneous use of Sporosarcina pasteurii bacteria and calcium nitrate-urea or calcium chloride-urea as a bacterial nutrient in the concrete mixture increased the 28 days compressive strength of concretes by 23.4% and 7.5%, respectively. The utilization of bacterial cells, nutrients, and culture in the concrete mixture provided the ability to heal wide cracks where the healing time was significantly reduced (about 8 days). On the other hand, separation of the bacterial culture medium slightly reduced the self-healing performance of the concretes.