Effect of Cracking Ages on Self‒Healing of Pure Fly Ash‒Based Engineered Geopolymer Composite

The effect of cracking ages (i.e., 3, 7, 14 d and 28 d) on the self‒healing of pure fly ash-based engineered geopolymer composite (FA-EGC) was evaluated by crack characteristics, tensile properties and water absorption. The components and microstructure of self‒healing products of FA-EGC were investigated by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The results show that there is an optimum self‒healing effect of FA-EGC samples when cracking age is 7 d, a better recovery of ultimate tensile strength and a reduction in average water absorption rate can be obtained at the maximum decrease in crack width. The self‒healing products of FA-EGC are the geopolymer gel generated by ongoing geopolymerization reaction and CaCO₃.