Measuring Three-Dimensional Damage in Concrete under Compression

To study the relationship between surface and internal cracking, 2 high-resolution, non-destructive evaluation techniques were used to measure crack growth caused by compressive loading in the fracture process of cement-based materials. Digital image correlation (DIC) was used to characterize the 2-D, surface fracture pattern, while 3-D, internal behavior was measured with x-ray microtomography (XMT). Rectangular mortar specimens containing both sand and graphite aggregates were examined. These techniques gave complementary information about crack geometry and development: DIC was more effective at determining crack width and location of small cracks, while XMT depicted the shape of larger cracks more successfully and showed the influence of internal features on the fracture process. The effect of aggregate shape and strength and the subsequent influence of increased crack distribution on ductility are discussed.