Bio-FM-Spray restoration of concrete pavement: Experimental investigation

This study explores bio-mineralizing bacteria and pore-fillers as an eco-friendly, cost-effective solution for autonomous crack healing in concrete pavement, addressing a key challenge in sustainable infrastructure maintenance. The methodology involved the spraying treatments using Sporosarcina ureae ( S. ureae ) and Bacillus subtilis ( B. subtilis ) suspensions, either independently or in combination with calcium silicate hydrate (C-S-H) as a filling material (FM) on the cracks appeared on the surface of concrete pavements. Controlled cracks ranging from 0.5 to 3 mm were intentionally introduced during the plastic state of concrete specimens. The Average Crack Area (ACA) index and healing efficiency was evaluated through visual inspection, image digitization, and image processing, complemented by FESEM/EDX, FTIR, and XRD analyses. The experimental results demonstrated that ACA index and healing efficiency was significantly influenced by treatment method and crack width. The FM spraying method showed superior performance in narrow cracks (0.5 mm), achieving approximately 97 % efficiency through C-S-H formation, while microbial treatments exhibited varying effectiveness through S. ureae demonstrated 66 % efficiency compared to 57 % for B. subtilis . Combining bacterial agents and FM established a dual healing system, demonstrating enhanced crack repair capabilities. FM alone achieved a high healing efficiency of 97 % at a 0.5 mm crack width due to C-S-H formation, while bacterial sprays reached 68 % efficiency for the same crack width via MICP. The synergistic effect was most pronounced at 1 mm cracks, where bacterial spray alone achieved 78 % efficiency while the combined treatment reached 73 %, demonstrating complementary healing mechanisms for enhanced structural recovery. As crack width increased to 3 mm, all treatments showed reduced effectiveness, though FM maintained better performance than biological methods alone, demonstrating an extended repair range. These findings highlight the importance of selecting repair strategies based on specific crack dimensions. • Spraying treatments with S. ureae and B. subtilis enhance self-repair. • Dual healing system combines biological and chemical mechanisms. • Crack width determines optimal self-healing treatment choice for concrete pavement.