Bio-inspired self-healing of concrete cracks using new B. pseudomycoides species

Bio-inspired self-healing of concrete cracks has been widely exploited to improve concrete properties and thus increase concrete life span using different bacterial species in recent years. The most common bacterial species found in the present literature are B. sphaericus, Sporosarcina pasteurii, Spore-forming alkali-resistant bacteria, B. megaterium and B. subtilis, while there is no published research using B. pseudomycoides species to heal concrete cracks. Furthermore, the need for more in-depth information on the healing ratio in the deeper part of the concrete crack remains. In the present study, a new bacterial species, namely B. pseudomycoides strain HASS3, was isolated, identified and tested for its ability to heal artificially cracked concrete samples. Both variable-pressure scanning electron microscope (VP-SEM) and X-ray computed microtomography (X-ray μCT) were utilised to assess the evolution of the healing ratio along with the crack profile. VP-SEM results revealed that a crack mouth width of 0.4 mm was fully healed through microbial precipitation which was later identified as calcite and vaterite using XRD. In contrast, according to the X-ray μCT results, the maximum healing ratio in the deeper part of the crack was only 14% compared to the crack mouth. As such, it could be concluded that bacteria-based concrete self-healing could function as a sustainable strategy to heal cracks located in the concrete skin.