Rate and Confinement Effects on Cracking and Failure in Uniaxial Compression ofConcrete

摘要

Crack patterns on longitudinal sections of specimens subjected to quasistatic andhigh-rate uniaxial compression, interrupted after various levels of maximum strain, so that intact specimens could be recovered, were examined. Damaged specimens were stabilized by an infiltrant containing a fluorescent dye to make the cracks stand out clearly under ultraviolet light, facilitating automated image analysis. Macroscopic cracking began near the lateral surface at maximum strains less than the peak-stress critical strain, and spread inward. The image analysis showed that total crack length, number of branch points, and number of end points, each reckoned per unit area, all increase roughly linearly with strain, with dynamic values significantly higher than static values at each level of maximum strain. When branch and end point counts were plotted against crack length per unit area, however, the static and dynamic plots coincided, showing that the crack pattern structure was determined by the microstructure of the medium, while all the rate dependence of the mechanical response was a result of the rate dependence of the evolution of a crack density parameter related to the crack length per unit area.... Concrete, Rate effects, Damage, Cracking, Compressive tests, Petrographic examination, Stereology automated image analysis, Failure.