Experimental on repair performance and complete stress-strain curve of self-healing recycled concrete under uniaxial loading

Abstract

The inherent brittle nature, low tensile strength and poor cracking resistance of concrete make it prone to cracking, which leads to the reduction of structural load-bearing capacity. Therefore, based on the loose and porous characteristics of the old mortar attached to the surface of the recycled aggregate, this study prepared self-healing recycled concrete with recycled aggregate as microbial carrier and investigated its crack healing capacity and uniaxial compressive stress–strain full curve. 24 specimens were designed for loading tests, namely: carrier adsorbed bacteria recycled concrete (C-BRC), direct-blended bacterial recycled concrete (D-BRC), no bacteria recycled concrete (NRC), and recycled aggregate concrete (RAC), and were further explored by Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS) and Mercury Intrusion Porosimetry (MIP) tests. The crack healing capacity, stress process and failure mode of each specimen were observed, and the repair performance, complete stress–strain curve, peak stress, peak strain, elastic modulus and Poisson's ratio of each specimens under different conditions were analyzed, and the mechanism analysis of mechanical properties recovery were investigated. The study showed that when the specimen were repaired for 28 days, all the cracks in the C-BRC were repaired to 100% with a maximum healing crack width of 0.27 mm. At the same healing time, the C-BRC had the best healing capacity, followed by the D-BRC, and the NRC had the lowest. The geometric characteristics of the stress–strain curve for self-healing recycled concrete prism specimen under uniaxial compression and the failure mode were similar to those of recycled concrete and ordinary concrete. At 56 days after healing, the peak stress recovery ratio of the C-BRC reached 86.94%, which was 37.01 MPa. The repair performance, peak stress, peak strain and elastic modulus of each specimens increased in different degrees with the increase of healing time. The Poisson's ratio of self-healing recycled concrete was measured to be roughly 0.16–0.23, which is slightly larger than that of recycled concrete.