Bacteria-based Self-Healing Concrete Technology utilizing Urease-positive Bacillus species isolated from Lahar sediments in the Philippines

Abstract

Compressive strength, durability, and porosity are some of the substantial assets of the
commonly-utilized construction materials, the concrete. However, these properties are inevitably affected by
environmental stresses such as freeze-and-thaw reactions, mechanical forces, earthquake, acid rains, and
weathering, leading to increased concrete porosity resulting in concrete cracks. The cracks formed on
concretes can further lead to deterioration, making the concrete quality inferior. To address the problem, the
study aimed to discover technology to strengthen concrete and promote concrete self-healing, using
microbial resources which promote self-healing in concrete, thus, reducing the cost for the repair of concrete
materials. Here, we isolated Bacillus species from lahar sediments in the province of Pampanga, the
Philippines, and determined their self-concrete healing property. The bacterial isolates were screened using
microscopic and biochemical techniques and identified them by 16s rRNA gene sequence analysis. The
bacterial species were cultured, inoculated, and mixed with the concrete. The self-healing property of the
bacteria was evaluated by evaluating the changes on the concrete cracks on the surface, subjecting to
compressive strength test, and assessed surface porosity by Scanning Electron Microscopy (SEM). The
results reveal urease-positive bacteria identified as Bacillus wiedmannii and Bacillus thuringiensis. The
bacterial concrete added with B. wiedmannii inoculum was found to have higher compressive strength,
higher compactness, and density as compared to the control group. Further investigation on the application
of B. wiedmanii on other concrete materials with different admixtures and subjecting in different
environmental conditions shall be explored to confirm the application of the bacteria as a self-healing agent
in field conditions.