Self-healing capability of engineered cementitious composites with calcium aluminate cement

Abstract

The reduced heating temperatures required for producing calcium aluminate cement (CAC) make it highly suitable for reducing CO2 emissions in engineered cementitious composites (ECCs) known with their significant amount of cement. However, it is not clear to what extent this can influence the advanced mechanical and self-healing ability of control ECC, especially with the risk of conversion in CAC reaction products. This study investigates the self-healing capability of ECCs produced using CAC instead of conventional ordinary Portland cement (OPC). It also assesses the impact of incorporating fly ash (FA) into CAC-ECC blends at different FA/CAC ratios. In addition to the mechanical characterisation of sound specimens, flexural properties, cracking behavior, ultra-sonic pulse velocity (UPV) and rapid chloride permeability test (RCPT) were performed on preloaded OPC- and CAC-ECCs. The study also analyzed the microstructural changes of self-healing products associated with the high alumina content of CAC. The results show that CAC can be used to produce high mechanical strengths ECCs, with more than 34% and 7% higher compressive and flexural strengths respectively than those of ECC-CTL at early age, though the addition of FA was important to reach improved patterns of mechanical properties at advanced ages. In addition, significant improvements were recorded for the recovery rates of CAC-ECCs, reaching more than 29% for flexural strengths, 11% for UPV and 75% for RCPT than the ECC-CTL. The self-healing products characterized with SEM-EDS confirmed the occurrence of conversion when FA was not included in CAC-ECCs, nevertheless with limited effect on the self-healing efficiency of these mixtures.