Microtomographic measurements of internal damage in portland-cement-based composites

The internal cracking patterns of a series of small mortar specimens were observed using a technique called X-ray microtomography. The experiments were arranged such that three-dimensional images of internal cracks could be made at several different times during the load history of the sample. This arrangement allowed progressive crack growth to be observed at micron-scale resolution in a single specimen. The specimens were loaded in compression. Image processing routines were used to make quantitative measurements of internal crack growth and damage progression. Preliminary measurements indicate that the maximum increase in crack area occurs around the peak load. Three-dimensional renderings qualitatively illustrate features of internal cracking such as the effects of different microstructural features.