Bio-based admixture for self-healing cement-based mortar

Abstract

Factors affecting the durability of concrete structures are generally associated with each other. Due to its brittle nature, concrete can crack under stress and these cracks are one of the main reasons for a decrease in service life in concrete structures. Recently, interest in using biomineralization processes for self-healing applications in cement-based materials has gained broader attention in the field. Biomineralization is a biochemical process in which microorganisms stimulate the formation of minerals, and in this particular case calcium carbonate (CaCO3). Due to the restricted environment of cement paste matrix, the main challenge is to find a microorganism that can tolerate the high alkaline conditions, can survive the mixing process, and can remain viable with limited access to nutrients and space to remediate cracks. This paper summarizes the results of a study undertaken to investigate the possible application of a bio-based admixture consisting Sporosarcina pasteurii (S.pasteurii) cells and urea-corn steep liquor (UCSL) medium to remediate flexural cracks in cement-based mortar. To develop biogenic self-healing agent, vegetative S. pasteurii cells were grown in UCSL medium and then mixed with cement and sand. Incorporation of cells, as well as the nutrient medium,,,did not affect the compressive negatively. Biogenic CaCO3 crystals were observed inside the flexural cracks and precipitates were able to seal cracks as large as 0.2 mm and decrease the permeability of the material.