Compressive fatigue behaviors of ultra-high performance concrete containing coarse aggregate

In this work, the uniaxial compressive fatigue behaviors of ultra-high performance concrete containing coarse aggregate (UHPC-CA) were investigated, towards a better understanding of the role of CA on its fatigue responses. Upon the constant amplitude fatigue tests performed at three stress levels (i.e. S = 0.7, 0.8, and 0.9), the emphases were focused on the effects of CA content (10%, 20%, and 30%) on the failure pattern, deformation characteristics, fatigue life, failure mechanism, and damage evolution. The results showed that compared to the UHPC specimen free of CA, the crack propagation, strain development, and fatigue life of UHPC-CA specimens are largely affected by the CA incorporation, due to the introduction of weak interfacial transition zones and the interference of fiber distribution. As a result, the risk of premature fatigue failure of UHPC-CA will be generally amplified as the CA content increases. Furthermore, inspired by the experimental observation that the fatigue failure strain of UHPC-CA stably approaches the descending branch of the monotonic stress-strain curve, a modified model based on the strain development instead of highly scattered fatigue life was proposed to estimate the nonlinear evolution of the fatigue damage. The good agreements with independent test results demonstrated the applicability of the model, representing a compromise between accuracy and practicability.