Developing Bio-Based Self-Healing Concrete: An Eco-Friendly Strategy for Sustainability of Concrete

There is a growing global demand for concrete, making it crucial to develop sustainable concrete solutions that address environmental concerns. Currently, approximately ۷% of total human-caused CO۲ emissions in the atmosphere come from cement production material. Techniques that incorporate bacteria to increase the lifespan of concrete elements will not only enhance their longevity but also contribute to more sustainable concrete materials for future generations. In this research, four different proportions of bacteria (۰.۵%, ۱.۵%, ۳.۵%, and ۵%) and nutrients (۰.۱۰%, ۰.۳۰%, ۰.۵%, and ۰.۷۵%) were used relative to the weight of the cement. The objective of this research is to assess the capacity of bacteria to function as self-repairing agents in concrete elements, specifically their ability to fix cracks by producing spores that form within the concrete. The spores of the bacteria mixed directly into the concrete mixture remained viable for an extended period. The gradual reduction of pore diameter during the concrete setting likely limited the longevity and reproduction of spores, as the pore widths were reduced to ۱µm or less. However, concrete mixed with bacteria exhibited a significantly higher production of minerals that fill cracks compared to normal concrete specimens. At various time intervals, the samples were tested for their compressive strength and microstructural characteristics using EDX, SEM, and XRD. The most significant improvement occurred at ۲۸ days, with proportions of ۱.۵% bacteria and ۰.۳% calcium lactate relative to the weight of the cement, resulting in a ۲۷.۱% increase in compressive strength and the healing of cracks measuring between ۱ and ۳ mm. This suggests that the use of bacterial spores as a self-sealing agent holds enormous potential.

Keywords:

Self-healing concrete , Bacteria , Calcium carbonate , Durability , Sustainable concrete development and strength