Bio Inspired Techniques To Enhance The Immunity of RC Members Against Corrosion

Abstract

Managing concrete scraps and agricultural wastes are major concerns of the society. They are causing climate change and obstruction to sustainability. In this scenario, engineering maintainable concretes and recycling of wastes have attracted huge attentions of scientists and engineers in the recent years. Under severe physical conditions, micro-cracks produced in the concrete provide pathways for aggressive substances to penetrate and cause corrosion of the embedded steel, hence destroying the strength of concrete. Using self-healing concretes have been proposed as the reliable solution, where bio inspired self-healing concretes are of special interest. Incorporation of a bacterial specie into concrete along with micro-nanomaterials precipitate CaCO3 which helps to patch the micro-cracks. Further, bacterial species form a thick sticky biofilm at the moisture-air interface which inhibits corrosion attack on the embedded steel bars. In this study, Bacillus Subtilis bacteria, being alkaliphilic, higher spores forming and having longer survival in dormant stage, were immobilized in micro-nanomaterials. Where micro-nanomaterials were obtained from bagasse sugarcane by pyrolysis process, acting as carbonized inert media. Porous biochar showed the best compatibility with host matrix by giving additional reinforcement in crack repairing and safely housing the bac-teria during concrete mixing and curing. Specimens were cracked by pre-loading at 85% of 28 days compressive strength. Biochar immobilized bacterial spores showed copious amount of cal-cite precipitation in cracks, highest compressive strength recovery and maximum improvement in impermeability and ultrasonic pulse velocities. Immunity against corrosion was checked by elec-trochemical testing techniques and results showed that biochar immobilized spores were more ef-ficient than control sample. Bacterial samples showed excellent bond strength of steel and concrete due to the formation of a thick sticky layer at their interface. The samples were characterized by scanning electron microscopy and energy dispersive x-ray spectroscopy, which confirmed the pep-tides like morphology and elemental composition of the steel bars was similar to the uncorroded steel. Consequently, Bacillus Subtilis bacteria immobilized in bagasse biochar could be considered as an excellent candidate for micro-crack healing in concretes and corrosion inhibition of steel bars.