Enhancing Concrete Performance: An Experimental Study on the Influence of Escherichia coli Bacteria on Split Tensile Strength

Abstract

Concrete plays an essential part in the construction industry universally, but its tendency to crack and its inadequate tensile strength often leads to the durability issues with time. The strength of concrete directly affects the overall life of a structure, and one of the most common issues affecting its strength is the formation of cracks. Cracks can form due to several factors, including lower tensile strength, a high water-cement ratio, shrinkage, or excessive settlement of soil. Conventional repair methods widely used, tend to be expensive, time-consuming, and often require frequent maintenance. This study reports the outcomes of an experimental analysis carried out to evaluate the influence of self-healing agent such as Escherichia coli (E. Coli) bacteria, on split tensile strength properties of concrete. Cylindrical samples of 100mm x 200mm size were prepared using M30 grade mix design with two groups of 4% and 5% bacterial solution along with 5% calcium lactate as a nutrient. After standard curing for 7 and 14 days, half of the samples were tested directly for split tensile strength, while the remaining bacterial concrete samples were cracked using a Universal Testing Machine (UTM) and then cured again to see their healing and strength regaining. The results showed that the concrete samples with 4% bacterial solution exceeded the strength of normal concrete by 14.41% and 18.63% after 7 and 14 days of curing respectively. On the other hand, the 5% bacterial concrete sample showed improved strength compared to normal concrete. After cracks were introduced, the bacterial concrete samples began to regain strength over time as they continued to cure. The sample with 4% bacterial solution regained

about 30% of its strength after 7 days and increased to 35.4% after 14 days. Similarly, the sample with 5% bacterial solution recovered 27% of the strength at 7 days and 36.4% after 14 days. While the initial healing wasn't significant, the results clearly showed that the longer the concrete was allowed to cure, the better was the strength regain. These findings support the potential of bacterial concrete as an innovative, low-maintenance and environment friendly solution that can enhance the durability and lifespan of concrete infrastructure.