Use of natural minerals as protective barriers of bacteria for self-healing mortar

Abstract

Microcracks are one of the main reasons for decreasing service life of concrete structures. Recent research in the field of concrete materials suggested that it might be possible to develop a cement-based material that is capable of remediating microcracks by triggering biogenic calcium carbonate (CaCO₃). This paper summarizes the study undertaken to investigate the influence of a 2-pahse biogenic self-healing agent on fresh and hardened properties of cement-based materials. To develop biogenic self-healing agent, S. pasteurii cells were immobilized to the locally available, lightweight and porous natural minerals such as bentonite, diatomaceous earth, and sepiolite. In addition, a portion of the minerals was saturated with a nutrient medium including urea and calcium acetate. Upon immobilization, minerals including cells and the nutrient medium were incorporated in the mortar mix. The mortar mix samples were evaluated in terms of fresh and hardened state performance such as workability, initial set and, compressive strength. Incorporation of cells, as well as the nutrient media with the minerals did not affect the initial setting of the mix negatively, however, a substantial decrease was observed in compressive strength of samples particularly prepared by minerals only including nutrient medium . However, depending on the practical application of the mortar, this two-phase immobilization system can be potentially used for self-healing.