Multiple Cracking and Fiber Bridging Characteristics of Engineered Cementitious Composites under Fatigue Flexure

The flexural fatigue characteristics of two different shotcreted engineered cementitious composites (ECCs) containing polyvinyl alcohol (PVA) and polyethylene (PE) fibers respectively were tested under four-point bending. The failure mechanisms and characteristics were investigated in comparison with a shotcreted steel fiber reinforced cement. The results showed that both ECCs exhibited a unique fatigue stress–life relationship that is represented by a bilinear function on a semilogarithmic scale. The failure mechanism of ECCs involved the development of multiple cracks, and the number of cracks was higher when the fatigue stress level was higher. The difference in crack opening displacement results from their different fiber bridging characteristics. PVA fibers tended to break under fatigue, while PE fibers tended to pullout. Although PE-ECC provided more cracks at the same fatigue stress, level, PVA-ECC showed larger deformation than PE-ECC because each crack width of PE-ECC was smaller than that of PVA-ECC. The deformation is shown to be governed by the number of cracks as well as the crack width, where the fiber bridging characteristics are related to either fiber rupture or fiber pullout.