Self-Healing Biogeopolymers Using Biochar-Immobilized Spores of Pure- and Co-Cultures of Bacteria

Abstract

A sustainable solution for crack maintenance in geopolymers is necessary if they are to be the future of modern green construction. This study aims to develop self-healing biogeopolymers that could potentially rival bioconcrete. First, a suitable healing agent was selected from Bacillus subtilis, Bacillus sphaericus, and Bacillus megaterium by directly adding their spores in the geopolymers and subsequently exposing them to a precipitation medium for 14 days. Scanning electron microscope with energy-dispersive X-ray (SEM-EDX) analysis revealed the formation of mineral phases for B. subtilis and B. sphaericus. Next, the effect of biochar-immobilization and co-culturing (B. sphaericus and B. thuringiensis) on the healing efficiencies of the geopolymers were tested and optimized by measuring their ultrasonic pulse velocities weekly over a 28-day healing period. The results show that using co-cultured bacteria significantly improved the observed efficiencies, while biochar-immobilization had a weak effect, but yielded an optimum response between 0.3–0.4 g/mL. The maximum crack width sealed was 0.65 mm. Through SEM-EDX and FTIR analyses, the precipitates in the cracks were identified to be mainly CaCO3. With that, there is potential in developing self-healing biogeopolymers using biochar-immobilized spores of bacterial cultures.

Exploring the Potential of Polypropylene Fibers and Bacterial Co-Culture in Repairing and Strengthening Geopolymer-Based Construction Materials

“…The two strains were selected due to their alkali tolerance, spore-forming ability, high potential for precipitating calcite, and non-pathogenicity. In addition, Doctolero et al [22] employed these bacteria and found that co-culturing bacteria significantly enhanced the healing efficiency of the geopolymer mortar.…”

“…Schaeffer-Fulton staining was used to confirm sporulation while spore concentration was measured using a hemocytometer. All samples were utilized immediately to avoid germination [22].…”

“…They achieved a maximum compressive strength of 55.78 MPa after a 56-day curing period. The self-healing effectiveness of the geopolymer material was found to be greatly improved by co-culturing Bacillus sphaericus and Bacillus thuringiensis as studied by Doctolero et al [22], with the observed maximum fracture width being 0.65 mm. Tian et al [23] directly applied Sporosarcina pasteurii in fly-ash-based geopolymer mortar and noticed a strength improvement of 16 to 45% with appropriate MICP formulations.…”

A biological cleaning agent for removing mold stains from paper artifacts

“…The ascospores were collected using method referenced in [30][31][32] and incubated at 28°C (fungi) or 37°C (bacteria) for 2 ~ 4 days. After spore germination, the spores were transferred to PDA and LB for subsequent molecular biological identi cation after single colony formation.…”

Isolation and Characterization of Indigenous Ureolytic Bacteria from Mindanao, Philippines: Prospects for Microbially Induced Carbonate Precipitation (MICP)

“…To date, this is only the second work in the Philippines to use indigenous bacteria for MICP. The first paper was published by Doctolero and coworkers [28], which used bacteria from the Philippine National Collection of Microorganisms (University of the Philippines Los Banos)-Bacillus sphaericus (BIOTECH 1272), Bacillus subtilis (BIOTECH 1679), and Bacillus megaterium (BIOTECH 1512)-isolated in the past from Laguna in the northern island of Luzon. These authors used these bacterial species to induce "self-healing" properties in oven-cured biochar-containing geopolymers and successfully sealed cracks having sizes between 0.1 and 0.65 mm via MICP.…”