The self-healing properties and mechanism of the cracked fly ash-based engineered geopolymer composites (FA-EGC): effects of water and temperature

In this article, the self-healing properties and mechanism of cracked fly ash-based Engineered Geopolymer Composites (FA-EGC) in different environments are studied. Four kinds of environments (air, wet-dry cycles, 20 °C water, and 40 °C water) are chosen to simulate real service environments. The tensile property, ultrasonic pulse velocity, crack characteristic, and water absorption of FA-EGC are measured to evaluate the self-healing properties. The test results show that the existence of water and the increasing of temperature can benefit the self-healing performance of FA-EGC. In addition, the 28-day self-healing products are determined by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) to explore the mechanism of the self-healing in different environments. The results demonstrate that N–A–S–H gels could be the main self-healing products in the air condition. While in the other environments with water, the (N/C)–A–S–H gels would be the primary products.