Synthesis and characterization of bio-immobilized nano/micro inert and reactive additives for feasibility investigation in self-healing concrete

Abstract

Bacteria-based self-healing concrete can be made more efficient by using immobilization techniques, hence shielding the bacteria from crushing during mixing to remain dormant till the development of concrete cracks for the uniform healing of developed cracks. In this study, two intrusion approaches, direct induction and immobilization, are deliberated by using ‘Bacillus subtilis’ bacteria for self-healing concrete. Furthermore, for immobilization’s evaluation, two media namely iron oxide nano/micro particles (INMPs) and bentonite nano/micro particles (BNMPs) were selected. Compressive and tensile strengths were computed at 3, 7 and 28 days. Moreover, field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray fluorescence (XRF) and thermo-gravimetric analysis (TGA) were employed for monitoring self-healing efficiency. Results revealed that immobilization through INMPs media was best among all intrusions ensuing successive healing of cracks up to 1.2 mm width having 85% recovery in compressive strength after pre-cracking. Whereas, BNMPs immobilization and direct induction exhibited crack healings up to only 0.15 mm and 0.45 mm crack healing widths with 45% and 65% strength recovery, respectively.