Comparative Analysis of Bio-Inspired Self-Healing Concrete with Distinct Carbon-Based Immobilizers

Abstract

In today’s world, development of infrastructure is an essential component of countries progress and prosperity. A major concern regarding this construction is development of Micro and Macro cracks. These cracks allow water passage towards steel rebar’s causing corrosion. Consequently, structure experiences loss of integrity, bad appearance, and reduced life. Thereby, requiring very costly rehabilitation and repair work using various techniques. In this research self-healing property of concrete has been explained using a varying concentration of cheaper carbonaceous material extracted from industrial waste (tyres) and commercially available Graphitic Nano/ Micro Platelets (GNMPs) as a carrier compound for bacteria to see whether it is equally effective in enhancing the mechanical and self-healing properties. At optimum concentration of 1.25 wt. % of GNMPs induced concrete samples, Flexural strength is 28% higher as compared to PCM and 76% higher as compared to BSM samples. Similarly, Flexural strength of 0.9 wt.%, waste tyre Biochar (WTBC) induced concrete sample is only 6% higher as compared to PCM and 46% enhanced as compared to BSM samples. The reason of increase is mainly because of the GNMPs and WTBC added in the cementitious matrix are effectively acting as nano/micro reinforcements, delaying the cracks nucleation and propagation in the sample. Samples with 0.9% GNMPs and 1.25% WTBC shows maximum compressive strength. Due to filler effect of very fine particles of added carbonized inert, Compressive strength of 0.9 wt.% GNMPs induced concrete sample is 80.6% and 13% higher as compared to PCM and BSM samples, respectively. Similarly, Compressive strength of 1.25 wt. % WTBC induced concrete sample is 90% and 18% higher as compared to PCM and BSM samples, respectively. GNMPs and WTBC served as effective immobilizer for long term survival of microbes of Bacillus Subtilis with enhanced crack filling efficiency. Samples with all proportions of GNMPs as an immobilizer confirmed healing of 0.5mm cracks. Almost all the cracks of 0.9 GNMP are fully healed at 60 days and maximum crack width healed is 1.2 mm by 2 wt. % GNMP and 0.8 mm by 2.5 wt. % WTBC. Strength recovery was also checked for all proportions after healing. Maximum microstructural improvement in 2.5 wt. % GNMPs and WTBC was recorded as 67.29 % and 78.46 %, respectively. which was confirmed by Ultrasonic pulse velocity (UPV). Subsequently SEM, EDX and XRD results confirmed healing product as Calcite.