Investigation of Biohealing Application for Micro-Size Fractures of Concrete Elements

In 2021, the American Society of Civil Engineers (ASCE) issued a report card with a cumulative infrastructure grade of C- and a grade of D for many of the U.S. infrastructure categories including roads, transit, and dams. The report states that “To improve our quality of life and strengthen our international competitiveness, we need a strategic and holistic plan to renew, modernize, and invest in our infrastructure”. (ASCE 2021). The goal of the proposed research is to evaluate the self-healing capacity of concrete when bacteria such as Bacillus spp., Pseudomonas spp., and Sporosarcina spp. are introduced in standardized and pre-manufactured micro-size fractures of concrete specimens under different environmental conditions. In previous research work, we have investigated the capacity of these bacteria to produce self-healing mechanisms, nevertheless, we have not been able to verify if this capacity is reflected in the increased strength of the material because the samples we have tested had different patterns and dimensions of cracks, due to the procedure used to manufacture them. 
In addition, we have verified that large fractures cannot be repaired using self-healing mechanisms. Based on these considerations, as part of the proposed research work, we aim to manufacture samples with a standard and controlled gap (i.e., fracture). The fracture will be created by inserting a Teflon wedge in concrete samples during manufacturing. The wedge will then be removed after curing the elements. Using the proposed procedure, it will be possible to verify the effects of the size of the crack on the capacity of bacteria of restoring the mechanical properties of the samples. Electron microscopy will also be employed to visually investigate calcite precipitation and the effectiveness of this phenomenon in repairing micro-scale fractures of concrete elements.