ENHANCING PERFORMANCE OF HIGH-STRENGTH CONCRETE USING BACILLUS MEGATERIUM AS SELF-HEALING AGENT

Abstract

The weak tensile properties of concrete allowed micro-cracks to emerge and propagate into macro-cracks if they were left undetected. An innovation called self-healing concrete (SHC) was subsequently introduced, allowing concrete to cover micro-cracks independently without any human intervention. SHC utilizes healing agents in the form of bacteria, which react with oxygen and water when cracks occur, resulting in calcium carbonate (CaCO₃) compounds that play a role in the concrete repair process. The aim of this study is to determine the effects of Bacillus megaterium on the compressive strength, flexural strength, depth of water penetration, and velocity of the 45 MPa high-strength concrete design based on ACI 211-4r.93 guidelines, with 25% of cement substitution by fly ash and 2% of bacteria percentage of the entire water composition. A 12.662% increase in compressive strength and a 1.690% increase in flexural strength were recorded for the age of 28 days bacterial concrete compared to the control concrete. The water penetration depth of the bacterial concrete was 4.49 cm, thereby meeting the DIN 1045 standard, which is less than 5 cm. From the ultrasonic pulse velocity (UPV) test, the average velocity value for bacterial concrete was 9.483 km/sec, which is categorized as having good concrete homogeneity based on the IS 1331 standard. This research offers promising insights into the SHC field by adding innovation to the design of high-quality bacterial concrete.