Advances in 3D image processing to evaluate damage and fracture of high-performance concrete

The three-dimensional images made possible by techniques such as x-ray computed tomography continue to provide us with new insights into fracture processes in concrete.Over the past 30 years, advances in both image acquisition and image analysis have improved to the point in which CT-based experiments are becoming relatively commonplace.In this work, we review some image analysis advancements and how they can be used to quantify the internal mechanisms that contribute to the complex problem of energy dissipation.The case study presented features a high-performance concrete with hybrid reinforcing consisting of conventional steel fibers, micro (steel wool) fibers, and a hybrid combination of both.50-mm diameter specimens were loaded in a split-cylinder configuration at quasi-static and low-velocity impact rates.The 3D image analysis broke the crack measurement problem into two parts: macro-cracking and micro-cracking.In this case, macro-cracks were defined as those visible in the images, while micro-cracks were those not visible.An edge detection algorithm was employed to measure macro-cracks, while a digital volume correlation method was used to estimate micro-cracking.Results showed a shift in micro-crack to macro-crack ratio as strain rates increased, although the result are highly dependent on the nature and orientation of the fiber reinforcements.