Growth and mineralization characteristics of Bacillus subtilis isolated from marine aquaculture wastewater and its application in coastal self-healing concrete

Abstract

There are many studies on the microbial remediation of cracks in cement-based materials in freshwater environments but fewer studies in marine environments, especially the use of bacterial strains with high mineralization ability obtained from marine aquaculture wastewater for coastal self-healing concrete. In this paper, the growth and mineralization characteristics of Bacillus subtilis (BS) isolated from seawater in shrimp farms were investigated, and the BS was used to repair coastal concrete cracks. Common Bacillus pasteurii (BP) was used as a control strain. The results showed that although the growth laws of the BS and the BP were similar, the mineralization ability of the BS was higher than that of the BP. In addition, in the process of crack self-healing, BS-induced calcium carbonate filled the mortar cracks (the initial crack width range was 0.20–0.25 mm), making the mortar cracks almost self-healing within 1 day, and its area self-healing rate was 2 times that of the BP mortar and 7 times that of ordinary mortar. This property of the BS can more successfully decrease the penetration of seawater into the mortars through cracks, improving the durability of its structures. These results have had a positive impact on the development of coastal self-healing concrete.