Autogenous self-healing of engineered cementitious composites under freeze-thaw cycles

In this paper, autogenous self-healing of engineered cementitious composites (ECCs) subjected to two different cyclic freeze/thaw (FT) regimes is investigated, which are water and deicing salt freeze/thaw cycles, respectively. To evaluate self-healing degree in preloaded ECC after FT cycles, direct tensile test, sorptivity test and ultrasonic pulse test are conducted for self-healed ECC with different preloaded strain levels varying from 0.5 to 3.0%. The experimental results show that self-healing of ECC mainly depends on preloaded strain levels which have a close relation with maximum crack width of preloaded ECC. Higher the preloaded strain level, lower self-healing degree. For ECC with preloaded strain levels of less than 1.5%, mechanical and transport properties of self-healed ECC can recover as well as those of virgin ECC without any damage. Water and deicing salt freeze/thaw cycles can weaken the properties of ECC. However, self-healing degree of ECC in water freeze/thaw cycles is higher than that in deicing salt freeze/thaw cycles. According to XRD analysis, chemical compositions of white self-healed cracks are calcium carbonate and calcium hydroxide.