Self-healing of Engineered Geopolymer Composites prepared by fly ash and metakaolin

This work focuses on investigating the self-healing characteristics and mechanism of Engineered Geopolymer Composites using fly ash and metakaolin as the precursors (MFA-EGCs). The hardened specimens were preloaded to different tensile strain levels followed by exposure to air and wet-dry cycles allowing for self-healing. Apart from the cracking characteristics, tensile properties were studied together with chemical and microstructural analyses. The results revealed a pronounced multiple cracking pattern and strain-hardening behavior for the MFA-EGCs. The number of cracks decreases significantly after the self-healing. High recovery ratios of the tensile strains and the ultimate tensile strengths were found, with some studied specimens showing even better tensile properties than the control specimens. It seems that air exposure is more favorable for the self-healing of the MFA-EGCs compared with exposure to the wet-dry cycles. Based on the results from SEM-EDS, XRD and FTIR, it was concluded that amorphous aluminosilicate phases are the main healing products.