Performance Evaluation of Multi-Bacterial Self-Healing Concrete Incorporating Bacillus Subtilis, Bacillus Megaterium and Pseudomonas Aeruginosa for Enhanced Mechanical and Durability Properties

Abstract

The deterioration of reinforced concrete structures as a result of concrete cracking is a prevalent issue, which leads to increased permeability, corrosion of reinforcement, and decreased service life. Although bacterial self-healing concrete has been widely researched, the majority of studies have been limited to the use of single bacteria species; very few studies have been conducted using multi-bacterial consortia and evaluating the overall synergistic effects of using multiple bacteria. This paper presents new quantitative data on binary combinations of Bacillus subtilis, Bacillus megaterium, and Pseudomonas aeruginosa, that were incorporated into M20 concrete using method direct addition at levels of 10 ml/L, 50 ml/L, and 100 ml/L of mixing water. Calcium lactate (2% by mass of cement) was used as a nutrient source in order to promote Microbial Induced Calcium Carbonate Precipitation (MICP). Results show that significant improvement occurred with the use of bacteria in concrete; specifically, the AC-100 and BC-100 mixtures produced the highest compressive strength of 29.2 MPa (31% increase), while AB-100 and BC-100 produced the highest flexural strength of 4.1 MPa (24.2% increase). The highest UPV value of 4.50 km/s was also produced by the BC-100 mixtures and demonstrated a 53.8% decrease in water penetration. The current study is limited to 28-days of laboratory tests only; therefore, long-term field based validation and microstructural testing such as SEM and XRD are required for further evaluation. The results from this research have demonstrated the potential of multi-bacterial concrete to serve as a sustainable and durable alternative for infrastructure applications. SEM and XRD analyses confirmed extensive calcium carbonate precipitation, pore refinement, and matrix densification through the Microbially Induced Calcium Carbonate Precipitation (MICP) mechanism, resulting in effective healing of cracks ranging from 1 to 5 mm.