Autogenous self-healing of polypropylene fiber reinforced ettringite-based composite

This study intends to advance the poor knowledge on the ability of an ettringite-based binder to obtain autogenous self-healing and its relevant mechanism. We developed a high-performance polypropylene fiber-reinforced cementitious composite using a slag-based ettringite binder and investigated its autogenous healing property under water-saturated conditions. Cracks were created via four-point bending loads on prismatic specimens at different crack opening displacements (i.e., 0.5, 1, and 2 mm in total crack opening). After curing times, the mechanical retention and recovery of the damaged composite were compared with the sound sample. We found that the material effectively heals micro cracks (i.e., under 100 μm) after 1 month of aging, while larger cracks could not completely close during the total curing times (up to 3 months). The healing products were mainly CaCO3 and ettringite observed through both experiments and thermodynamic modelling. These crystals mainly formed from the carbonation of ettringite and other AFm phases in aqueous conditions. The strength retention slightly reduced (about 10%) after healing, however, the composite still exhibited deflection-hardening behavior. Findings show the high potential of ettringite-based binder to be a matrix for self-healing cementitious composites. Further improvements, nevertheless, are needed to increase the healing rate and strength recovery of the composite.