Repeatability of self-healing in cementitious composites

In this paper, intrinsic self-healing ability of Engineered Cementitious Composites (ECC) was investigated in terms of two robustness criteria; repeatability and pervasiveness. To do this, different composites with Class-F fly ash (F_ECC) and slag (S_ECC) were examined. In order to generate microcracks, specimens were repeatedly pre-loaded up to 70% of their deformation capacities under splitting tensile loading and exposed to cyclic wet/dry conditioning thereafter. Resonant frequency (RF) and rapid chloride permeability tests (RCPT) were utilized to assess the extent of damage and final results were supported by the microscopic observations. RF measurements were recorded from two different parts of the specimens to monitor if self-healing was pervasive. Results show that depending on the type of mineral additive and initial curing time, ECC specimens can recover up to 85% of their initial RF values even after six repetitive pre-loading. Although, the extent is slightly less, the recovery rates observed from the middle portions are similar to those observed from the top portion of the all ECC mixturesimpliying that self-healing is quite pervasive. After the application of severe pre-loading for five times, RCPT results of both mixtures satisfy low chloride ion penetrability levels. Maximum crack width observed over the specimen surfaces is restricted to 190 µm level even after nine repetitive pre-loading. These findings suggest that under certain conditions ECC materials produced in this study may significantly enhance the functionality of structures by further reducing the repair and/or maintenance need. Keywords: Engineered Cementitious Composites (ECC); Self-Healing; Repeatability; Supplementary cementitious materials (SCM).