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.
