Technique to Measure 3D Work-of-Fracture of Concrete in Compression

A high-resolution 3D scanning technique called X-ray microtomography was applied to measure internal damage and crack growth in small mortar cylinders loaded in compression. Synchrotron-based microtomography allows us to resolve internal features that are only a few microns in size. Multiple tomographic scans were made of the same specimen at different levels of deformation using a custom-built loading frame. 3D image analysis was used to measure internal crack growth during each deformation increment. Measured load-deformation curves were used to calculate the nonrecoverable work of the external load on the specimen. Nonrecoverable work of load was related to measured incremental change in crack surface area to estimate work-of-fracture in three dimensions. Initial results indicate a nearly constant work-of-fracture for the early stages of crack growth. These results show that basic fracture mechanics principles may be applied to concrete in compression; however, we must think in terms of 3D multiple crack systems rather than traditional 2D single crack systems.