Self-healing and expansion characteristics of cementitious composites with high volume fly ash and MgO-type expansive agent

Discovering new cement based materials characterised with self-healing capability is essential for sustainable infrastructure with longer service life. Engineered cementitious composite (ECC) with high potential of micro-crack healing can enhance ductility and durability of concrete structures. MgO-type expansive agent (MEA) having low water demand and with the ability of densification of concrete microstructure was utilized in this research to develop ECC-MgO self-healing system. The effect of dosages of MEA and fly ash of different types as cement replacements was investigated based on lower expansion characteristics of ECC-MgO bar specimens through both water and autoclave linear expansion tests. The performance of ECC-MgO self-healing system was examined based on compressive strength recovery of pre-cracked cubic specimens and matrix micro-structural densification through Scanning Electron Microscope (SEM). Test results indicated that 5% lightly burnt MgO in combination with high volume of Class-F fly ash with 55% cement replacement should be used to design ECC-MgO self-healing system just to heal micro-cracks without affecting the durability. The higher compressive strength of 50% and 80% pre-cracked ECC-MgO cubic specimens cured under accelerated autoclaved conditions compared to ECC-control (without MEA) confirmed the self-healing capability and potential of the proposed ECC-MgO system.