Evaluation of Damage Affecting the Mechanical Behavior of Composite Materials
Laboratory mortar samples and large structures of concrete under tension most likely behave as brittle. Contrary to what is expected from a brittle material, the previously mentioned structures could: 1) develop distributed damage, 2) relax tensile stresses and 3) reduce its macroscopic tensile strength when subject to time-dependent tensile stress gradients. Time-dependent tensile stress gradients can be found in large concrete structures such as pavements and in laboratory samples like the restrained ring test. In those cases, tensile strength reduction means that the deterministic tensile strength obtained from standard tests, e.g. split tensile test, is over predicting its value. Up to now, there is no complete explanation on the mechanisms responsible for the quasibrittle behavior of laboratory size mortar and large structures of concrete under tension caused by time-dependent loading conditions. Mortar and concrete are part of the family of cementitious materials which together represent the most manmade produced material worldwide. Therefore, the main motivation of this research is to provide new insights that help bridge some of the remaining gaps in the literature. I aim to contribute to understand the age-dependent behavior and degradation of mortar and concrete at early ages. Based on a review and critical analysis of the state of the art in terms of experimental, analytical and numerical characterization, I proposed and develop of a phenomenological model, where solidification and a cohesive zone model with stochastic strength distribution are implemented in a finite element code to capture the behavior of laboratory size restrained mortar subject to nonuniform shrinkage.
Zavattieri, Purdue University.
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