CHARACTERIZATION AND MONITORING OF THE CRACK SELF-HEALING ABILITY OF BIO-MORTAR

It is known that bacteria can promote self-healing of the cracks in concrete structures, but the elevated pH value of the cement-based concrete matrix affects negatively the bacteria living time and consequently the self-healing effect. Therefore, a method for encapsulation of bacteria healing agent in a polymer hydrogel system has been successfully established to protect the bacteria from surrounding environment. In order to investigate the healing capacity of the employed bacterial colony and the effectiveness of the proposed encapsulation methods, three groups of mortar specimens were systematically prepared: standard reference samples, samples with hydrogel and bio-mortar samples (with bacteria species encapsulated in the hydrogel system surrounded with nutrition). Microstructure and texture analysis were performed before and after the healing treatment. The mortar specimens were notched at mid-span and pre-cracked by means of 3-point bending tests performed in CMOD-control mode. Water sorption tests were performed periodically in order to ascertain the effects of healing on the recovery of durability performance. The healing ability was also measured by crack opening displacement change by optical microscopy. The specimens were tested in 3-point bending up to failure, to assess the effect of the healing, if any. A cross-comparison analysis of the obtained results was provided.