PERFORMANCE EVALUATION OF BACTERIA IMMOBILIZED COCONUT SHELL BIOCHAR BASED SELF-HEALING CONCRETE AT ELEVATED TEMPERATURES

Abstract

Embarking on an innovative frontier, this study explores bio-inspired self-healing concrete. Imagine Coconut Shell Biochar (CSBC) as a catalyst, hosting Bacillus Pumilus (BP) spores, enhancing calcite (CaCO3) precipitation in High-Strength Concrete (HSC) even when faced with the blistering challenge of elevated temperatures ranging from 23°C to a scorching 800°C. This research unveils secrets from microscopic analysis captured by scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) to macroscopic evaluations where compressive strength, split tensile strength, mass loss, stress-strain response, toughness and elastic modulus portray a vivid image of concrete's resilience under fire. Results highlight the dynamic combination of BP spores and CSBC nano/micro particles, ensuring exceptional mechanical properties at room temperature. However, beyond the 200°C threshold, Biochar-enhanced Bacillus Pumilus High Strength Concrete (BPC-HSC) encounters the trial of thermal breakdown of calcium lactate, yet it outshines its counterpart, Bacillus Pumilus High Strength Concrete (BP-HSC), due to the presence of CSBC, maintaining remarkable strength. BPC-HSC's fracture energy boosts up at 600°C, attributed to thermal conductivity and crack bridging of CSBC particles, coupled with BP spores' self-healing. Individual assessments highlight the commendable performance of BP-HSC, showcasing substantial strength at ambient temperature. Nonetheless, it faces thermal challenges attributed to the decomposition of calcium lactate, as the temperature rises above 200°C. On the other hand, biochar-modified HSC (BC-HSC) stands resilient, demonstrating remarkable mass retention at high temperatures, solidifying its position as a robust material in elevated conditions. Coconut shell biochar emerges as a green and effective carbonaceous additive, enhancing concrete fracture properties, whether used independently or as a carrier for bacteria. Mathematical models articulate properties for all modified HSC formulations (C-HSC, BC-HSC, BP HSC, BPC-HSC) as a function of temperature. These findings contribute to understanding sustainable self-healing concrete systems, urging future investigations for thermally stable supplements for bacteria in elevated temperature conditions.