Influence of free water on compressive fatigue properties of ECC

Engineered cementitious composites (ECC) with strain hardening characteristics have potential applications in hydraulic structures subjected to repeated or fatigue loads. In order to clarify the effect of free water on the compressive fatigue performance of ECC, the compressive fatigue tests of dry, saturated and water-submerged ECC under different stress levels were carried out. The failure mode and S-N curve of ECC were determined, and the fatigue life of ECC decreased in turn under dry, saturated, and water-submerged conditions. The strain rate of the second stage of ECC compression fatigue increases with the increase of water content and stress level. The failure strain of ECC fatigue increases with the decrease of stress level, and the fatigue failure strain of saturated and immersed specimens is larger than that of dry specimens at the same stress level. In addition, the stress level-fatigue failure strain (P-S-epsilon) equation considering the failure probability is established. To improve the credibility of this equation, the confidence gamma is considered, and the gamma-P-S-epsilon curves of all samples are obtained, which can predict the fatigue failure strain of ECC at a specific stress level.