Enhancing the self-healing properties of engineered cementitious composites by the application of super-sulfated cement

No research has been reported on the self-healing performance of engineered cementitious composites (ECCs) prepared with super-sulfated cement (SSC), despite its potential to reduce carbon dioxide emissions compared with ordinary Portland cement (OPC). This significant gap in the research literature was addressed by exploring the influence of SSC on the recoverability of pre-cracked ECC samples. In addition to mechanical characterisation of sound samples, an exhaustive investigation was undertaken to comprehensively assess the self-healing ability of pre-loaded SSC-based ECCs by means of flexural strength tests, deflection measurements, ultrasonic pulse velocity (UPV) tests and rapid chloride permeability tests. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) was used to evaluate the microstructural changes and development of self-healing products within the microcracks of SSC mixtures prepared with various amounts of fly ash. The SSC-based ECCs, while maintaining comparable mechanical and ductility properties, exhibited significant improvements in recovery rates (more than 27%, 7% and 76% for flexural strength, UPV and chloride permeability, respectively, compared with the OPC-based control ECC). The SEM–EDS results confirmed the enhanced precipitation of ettringite as a new self-healing product related to the inclusion of SSC in ECCs, along with conventional calcium silicate hydrate/calcium aluminium silicate hydrate (C-S-H/C-A-S-H) gels.