Analysis of crack microstructure, self-healing products, and degree of self-healing in engineered cementitious composites

In this paper, self-healed cracks of engineered cementitious composites (ECC) are observed by optical microscope and scanning electron microscopy, and self-healing products of ECC are analyzed by X-ray diffraction technology. Meanwhile, the reasons for property differences between origin ECC and self-healed ECC with different crack structures exposed to freeze-thaw in water and deicing salt, respectively, are discussed. ECC specimens with a water-binder ratio of 0.25 with 50% fly ash are studied. The experimental results show that the white self-healing products and other chemical composites similar to the color of ECC matrix are present on the surface of self-healed cracks. The self-healing materials of ECC include kinds of hydration/carbonation products and some chemical compounds penetrating into ECC matrix from self-healing environments. Additionally, the differences in self-healing products and hydration products of binder, self-healing extent, damaged polyvinyl alcohol fiber, weak interface bonding, and microcracks could obviously influence the value variation of first cracking stress, ultrasonic pulse viscosity, and absorption coefficient of self-healed specimens.