| Summary: | High strength engineered cementitious composites (ECC) that fracture under tensile stress present cracks with the width over 100 μm, which may not be easily repaired by autogenous healing. Herein, this study investigated the healing efficiency of high strength ECC after being immersed in bacteria-free medium which is waste medium during spore cultivation. During incubation of bacteria, concentration of carbonate ions in the medium could rise to 0.30 mol/L approximately. These carbonate ions can be leveraged in calcium carbonate precipitation process for crack healing, which contributed to greater reduction of crack width of ECC specimens in waste medium than that in water. The superior crack closure led to the recovery of water tightness by lowering down the water absorption of cracked specimens and the restoration of tensile properties including both tensile strength and ultimate strain even after final failure of specimens. Therefore, it can be concluded that bacteria-free waste medium is promising to promote healing of concrete cracks.
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