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The fatigue failure characteristics of Engineered Cementitious Composite (ECC) were investigated by four-point flexural fatigue tests in comparison with two types of Polymer Cement Mortar (PCM). The fatigue failure mechanisms were observed, and the damage evolutions were measured for all shotcreted specimens. The results showed that ECC performs the improved fatigue life and that it exhibits a bilinear fatigue stress-life relation on a semi-logarithmic scale. ECC under fatigue loading shows much more ductility than PCMs, because the failure of ECC involves the initiation of multiple cracks, the propagation of those cracks, and the localization to a single crack, while the failure of PCMs involves only the initiation of a single crack.

This paper presents an experimental study on the flexural fatigue characteristics of PVA-ECC and PE-ECC. The ECCs showed a unique S-N relationship and exhibited the development of multiple cracks even under fatigue loading. The development of multiple cracks was found to be dependent on fatigue stress levels, and the mechanism is discussed in reference to the static multiple cracking mechanism. The difference between the two ECCs appeared especially in the deformation capacity under fatigue loading. The deformation is shown to be affected by the number of cracks as well as the crack width, where the fracture mechanism of a bridged crack is related to either fiber rupture or fiber pullout.

This paper proposes a fatigue analysis method of Engineered Cementitious Composite (ECC) under fatigue flexure by applying the concept of fiber bridging degradation. The mechanical degradation of materials under fatigue load is considered a major factor for fatigue crack propagation and subsequent fracture. FEM with the concept of both smeared crack and discrete crack is introduced for representing the consequences of multiple cracks and a localized crack , respectively. The bridging stress degradation law under fatigue load as well as the constitutive relation under static load is introduced as essential input material properties in the fatigue analysis. In order to verify the fatigue analysis, a flexural fatigue test program of two kinds of ECC, PVA-ECC and PE-ECC, was conducted. The fatigue characteristics of flexural beams predicted by the proposed model such as S-N relation and the evolution of midspan deflection agree well with those from the test results. It is also shown that the fatigue analysis is applicable to determine the bridging stress degradation relation of ECC by flexural fatigue tests .

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