Insights into self-healing capacity of cement matrix containing high-efficiency bacteria under challenging conditions

Abstract

This study provides novel insights into enhancing the self-healing capacity of cement matrix through the integration of natural Bacillus isolates derived from leached and calcified soils. The challenging and highly alkaline environment of cement matrix typically impedes bacterial activity, making the successful application of these bacteria in such conditions particularly significant. In this research, Bacillus licheniformis-Bacillus muralis co-culture was identified as highly effective in inducing calcium carbonate precipitation, a critical factor for self-healing. The selected co-cultured bacterial activity resulted in the formation of up to 2.885 g/100 mL of CaCO₃, while the co-culture's effectiveness was demonstrated by the complete repair of a 0.5 mm crack within 96 h demonstrating a repair rate of approximately 0.125 mm per 24 h. Furthermore, the study showed that the bacterial co-culture could survive and remain active under varying environmental conditions, including wet-dry cycles and extreme pH levels, which are typical of construction sites. This rapid crack closure, achieved without additional protective measures for the bacteria, marks a significant advancement in the application of microbial co-cultures for enhancing the durability of cement-based materials. The study also provides a detailed analysis of bacterial behavior under various environmental stresses typical of construction sites, highlighting the robustness and practical applicability of this biotechnological approach. As the long-term output, the obtained results represent a substantial advancement in the practical application of microbial co-cultures for self-healing effect of cement-based materials.