Using Bio-Based Self-Healing Agent for Durability and Environmentally Friendly Concrete Development

A growing global demand for concrete makes it crucial to develop durable concrete that addresses environmental concerns. Approximately 7% of total human-caused CO 2 emissions come from cement production. Bacteria-incorporated techniques that increase the lifespan of concrete will not only enhance durability but also contribute to creating more sustainable concrete-making materials for future generations. Traditional methods, such as epoxy injection, grouting, drilling, plugging, and gravity filling, are time-consuming, require additional maintenance, and negatively impact the environment. This research used four different proportions of bacteria (0%, 0.5%, 1.5%, 3.5%, and 5%) and nutrients (0.10%, 0.30%, 0.50%, and 0.75%) relative to the weight of the cement. The goal is to evaluate the ability of bacteria to function as self-repairing agents in concrete, specifically their capacity to repair cracks by producing spores. The spores, mixed directly into the concrete, remained alive for a specific period but became dormant when the pore size decreased below 1 µm until cracks formed. The gradual reduction in pore size during the concrete setting likely restricted the longevity and reproductive capacity of the spores as pore widths reduced to 1 µm or less. However, the concrete mixed with bacteria showed a significantly higher production of minerals to fill cracks than standard concrete specimens. Samples were tested at various intervals for compressive strength and microstructural characteristics using EDX, SEM, and XRD. The most significant improvement occurred at 28 days, with proportions of 1.5% bacteria and 0.3% calcium lactate relative to the weight of the cement, resulting in a 22.1% increase in compressive strength and healing of cracks measuring between 3 mm in diameter. This suggests that using bacterial spores as a self-sealing agent holds enormous potential.