Dual-functional GO-modified plant fibers regulate biomineralization and enable fiber-dependent wide-crack healing in mortars

Microbially induced calcium carbonate precipitation (MICP) is a promising approach for crack self-healing in cementitious materials, but its application to relatively wide cracks is limited by bacterial availability and by the difficulty of developing continuous mineral deposits across the crack space. Within the specimen-average initial surface crack-width range of approximately 0.3–0.7 mm evaluated in this study, local widths greater than 0.4 mm at the registered measurement positions were operationally classified as the relatively wide portion of the position-level crack-width distribution. A dual-functional self-healing system was developed by combining bacteria-immobilized expanded perlite (EP) with graphene oxide (GO)-modified coconut, bamboo, and sisal fibers. The combined oxidative–reductive pretreatment and GO loading reduced the 48 h water absorption of coconut, bamboo, and sisal fibers by 32.2%, 42.6%, and 43.7%, respectively. The GO-modified groups showed lower residual Ca²⁺ concentrations under static conditioning and higher culturable bacterial counts in mortar specimens than the corresponding unmodified-fiber groups; the 3 d count of GO-SF-B reached 1.68 × 10 ¹ ⁰ CFU·g⁻¹ . All fiber-containing groups achieved complete apparent surface crack closure at 28 d, while the GO-modified groups exhibited faster closure at 3–14 d, larger ultrasonic-pulse-velocity increases, and lower relative water permeability. GO-SF-B showed the strongest combined response, with an UPV increase of 26.70% and a relative water permeability of 0.84% at 28 d. Microscopic, mineralogical, spectroscopic, and thermal analyses identified calcite-dominated healing products and showed denser and more continuous mineral deposits in the GO-modified groups. The combined results support complementary functions of EP-based bacterial immobilization and GO-modified fiber-associated interfacial regulation, with a fiber-dependent response under the investigated conditions.