Mechanical Assessment and Crack Control in Concrete Using Carbonate Calcium Bioprecipitation with Bacillus Subtilis Bacteria

Abstract

This article aims to demonstrate the usefulness of microorganisms in the construction industry, specifically in improving construction materials, particularly concrete. In this case, Bacillus Subtilis bacteria were used, as they can produce calcium carbonate (CaCO₃), also known as calcite, through bioprecipitation. These bacteria were cultivated in the microbiology laboratory and mixed with concrete with a compressive strength of 21 MPa at the Universidad Militar Nueva Granada. From this experiment, it was observed that when the concrete mixture was prepared, the bacteria improved the workability of the mix. Subsequently, after curing and maturation, mechanical behavior tests were conducted, including compressive strength tests according to ASTM C39 and flexural strength tests according to ASTM C78 criteria. Additionally, scanning electron microscopy (SEM) analysis was performed to microscopically observe the bacteria's ability to produce calcium carbonate and identify the chemical elements present in the mixture. This was done to directly observe how the bacteria seal and control concrete cracks, resulting in the measurement of the properties of Bacillus Subtilis to generate calcite, which seals and controls concrete cracks—a process known as self-healing. This brings advantages to the concrete, such as increased durability, improved mechanical behavior, and reduced permeability.