An Investigation Towards the Fracture Occurrence of Self-Healing Concrete

Abstract

Concrete is the inescapable element of any development action, in view of its adaptability. In any case, it has a few constraints out of which one such significant viewpoint is that substantial is powerless in pressure so it has next to no protection from ductile powers and effectively defies to breaking. Moreover, these micro-cracks emerge once structure is subjected to loading and ultimately leads to the formation of macro cracks. This increases the permeability of concrete thereby reduce the service life of the building. In this regard, cracks are to be treated with the utmost care in order to increase the durability of the structure. Although there are several available chemical and physical methods, yet most of them require human intervention for repair work. Hence this research focuses on the novel autogenous healing mechanism using micro-organisms in the concrete. It heals micro cracks and increases the strength of concrete as well as the durability. Because it increases the service life of the structure can be considered as environmentally friendly.

Accordingly, this thesis has four objectives. First, we sought to isolate of the right kinds of bacteria which will close the cracks and increase the strength of concrete. Second objective was to examine the healing properties of microcapsules. Third, we sought to study the strength development in concrete such as compressive stress tensile and flexure strength of concrete with a different healing mechanism. Finally, we also intended to study the behaviors of crack under sustain loading condition. Towards the first objective, based on extant literature, we identified three types of bacteria, namely, Bacillus Pasteurii, Bacillus Sphaericus and Bacillus Subtilis from different sources. Findings suggest that all three bacteria used in the study could survive in the harsh concrete medium and were able to precipitate Calcium Carbonate. Towards the second objective, microcapsules were prepared by using in situ polymerization process with sodium silicate as the core material. The results revealed that microcapsules contributed to the healing of the crack. Towards the third research objective, tests were carried out using identified bacteria for different bacterial cell

concentration of 104, 105, 106 and 107 per ml with four different concrete mix designs namely M20, M25 grade concrete with and without mineral admixture (fly ash and silica fume) and M40 grade concrete with mineral admixture (fly ash and silica fume).