Biocementation: an eco-friendly approach to strengthen concrete

Abstract

Enhancement of the mechanical properties of cementitious materials by using ureolytic bacteria is a green technique and is gaining importance in today’s era of development and modernisation. This process is known as biocementation or microbially induced calcium carbonate precipitation (MICCP). In the present work, a bacterial solution using soil as a bacterial source was used. Lentil seeds were used as a protein source and sugar as a carbon source for the bacteria. Urea concentration plays a key role in the MICCP process as, on hydrolysis, urea produces carbon dioxide, which forms calcium carbonate in the presence of calcium ions. The precipitation of calcium carbonate in the concrete matrix augments the mechanical properties of concrete. Thus, by using readily available natural materials – soil and lentil seeds – concrete is strengthened. This would indirectly reduce the carbon dioxide footprint. An attempt was made to study the effect of various concentrations of urea on the mechanical properties of concrete. Significant increases were observed in compressive strength and split tensile strength and a reduction in the water absorption capacity of concrete for a urea concentration of 5 g/l. Survival of the bacteria in cementitious matrix was also monitored. The results showed that bacteria survive up to the fifth day of curing.