Autogenous and engineered healing mechanisms of carbonated steel slag aggregate in concrete

The application of self-healing technology in concrete materials was widely investigated in the past decade. Although the micro-capsules and bacteria were considered as promising self-healing agents to realize durability enhancement of concrete, the high cost of micro-capsules and limited bacteria types are still big challenges that limit the widely application of this technology. As a result, it is necessary to develop cost-effective and environmentally friendly materials as self-healing agent in concrete. In this study, carbonated steel slag was used as aggregate to realize the autogenous healing of concrete. The self-healing performance of this concrete was investigated by comparing with the concretes prepared with normal aggregates and crushed steel slag aggregates. In addition, the hydration heat, X-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy results were analyzed to elucidate the self-healing mechanisms of concrete via using carbonated steel slag as healing agent. It was found that the healing products are mainly composed of CaCO3, Ca(OH)(2), calcium-silicate-hydrate, calcium-aluminate-ferrite hydrate as well as amorphous silica. The cracks of aggregate have been healed to a certain extent that maximum healing width is about 20 mu m and maximum healing length is about 5 mm. (c) 2016 Elsevier Ltd. All rights reserved.