Bioconcrete Development Using Calcite -Precipitating Bacteria Isolated From Different Sources in Jordan

Abstract

Concrete is considered as the most widely used construction material in the world. However, concrete is exposed to cracks due to different factors like overloads, temperature, shrinkage, earthquakes and others. These cracks reduce the strength, the service life of the structure, and increase the permeability of the concrete. Thus, the importance of "self-healing concrete" is highlighted nowadays, with emphasis on a special type of concrete called bioconcrete, which is a concrete that has the ability to self-heal the microcracks that happen due to overloads. This ability comes from the bacteria used in the concrete mix which have special characteristics such as the ability to live in harsh conditions similar to those found in the concrete environment, in addition to their ability to precipitate calcite (calcium carbonate (CaCO3)), the sealing material in the cracks. This study aims to assess the performance of self-healing Bacillus mycoides incorporated into Portland cement mortar. This bacterium has been isolated from the soil of Fava beans in Jordan. Cracking of specimens was induced by load percent concept after 7 days of curing and tests were performed at 21 days of cracking. The testing scheme for the mortar included bacterial sporulation tests inside mortar specimens, acid fizz test and a compression test. Results demonstrated that self-healing bacteria is a promising technique in minimizing cracking. The rate of healing using bacteria was higher than the bacteria-free negative control.