Performance evaluation of self-healing recycled concrete using biomineralization modified recycled aggregate as bacterial carrier

Abstract

The development of bacteria-based self-healing concrete relies on a carrier that is both compatible with the concrete matrix and capable of effectively protecting bacteria. This study utilized biomineralization modified recycled aggregate (RA) as a bacterial carrier to create bacteria-based recycled concrete with a strong self-healing capability. The workability, compressive strength, durability and self-healing performance of concrete were evaluated. The results showed that the quality of RA was significantly improved after biomineralization modification treatment due to the filling of bio-calcium carbonate in surface pores and microcracks, with an increase in apparent density of 1.9%, a decrease in water absorption and crushing index of 13.9% and 15.3%. The modified RA can provide better bacterial protection, thereby enhancing the crack self-healing efficiency of concrete by forming more bio-calcium carbonate healing product. For cracks with a width of about 0.4 mm, after healing of 56 days, the crack width repair ratio of bacteria-based recycled concrete was 94.5%, with an increase by 61.0% compared to that (only 58.7%) of ordinary recycled concrete. X-ray diffraction (XRD) results showed that the bio-calcium carbonate was calcite. The improvement of RA's quality will also benefit the performance enhancement of concrete. Compared to ordinary recycled concrete, the 28d compressive strength of bacteria-based recycled concrete was increased by 16.6%, the capillary water absorption coefficient was decreased by 37.5%, and the workability and resistance to chloride ion penetration was significantly improved.