Performance Evaluation of MICP in Crack Repair: Strength and Durability Enhancement Using Different Bacterial Strains

Area of Science:

• Materials Science
• Civil Engineering
• Biotechnology

Background:

• Concrete cracking compromises structural integrity and service life by allowing aggressive agent ingress.
• Traditional concrete crack repair methods are often ineffective for micro-cracks and can release harmful compounds.
• Microbially induced calcium carbonate precipitation (MICP) presents a sustainable, bio-based solution for in situ concrete crack sealing.

Purpose of the Study:

• To compare the effectiveness of two MICP systems, one ureolytic (Sporosarcina pasteurii, SP) and one non-ureolytic (Bacillus mucilaginosus, BM), for repairing cracked concrete.
• To evaluate the performance of these MICP systems when utilizing a dual-viscosity-modifying-agent (VMA) system (Welan Gum and Attagel 50, WA).
• To assess the impact of crack width on the efficiency of MICP-based concrete repair.

Main Methods:

• External application of SP + WA and BM + WA repair systems on concrete specimens with crack widths ranging from 0.10 to 0.80 mm over 16 days.
• Evaluation of crack repair effectiveness using splitting tensile strength, capillary water absorption, rapid chloride migration (RCM), and X-ray diffraction (XRD) tests.
• Comparison of repair performance against intact control specimens to quantify property recovery.

Main Results:

• The SP + WA system demonstrated superior performance compared to BM + WA, showing higher tensile strength retention (59.57-68.95% vs. 56.68-67.15%) and better recovery of capillary water absorption (58.36-64.81% vs. 51.71-58.02%).
• Chloride resistance and RCM (D_RCM) recovery were significantly higher with the SP + WA system (63.7-82.1% and 57.35-77.68%, respectively) compared to BM + WA (50.5-60.0% and 46.04-61.00%).
• Repair efficiency decreased with increasing crack width for both systems. XRD analysis confirmed calcite as the primary CaCO3 polymorph, with SP + WA yielding sharper peaks indicative of distinct calcite crystal characteristics.

Conclusions:

• The dual-VMA-assisted MICP approach effectively enhances the mechanical and durability properties of cracked concrete.
• The ureolytic SP + WA system exhibits superior repair performance compared to the non-ureolytic BM + WA system.
• MICP-based concrete repair shows promise as a sustainable solution, with performance influenced by bacterial type and crack width.