Technique to measure 3D work-of-fracture of concrete in compression

A high-resolution 3D scanning technique called X-ray microtomography was ap plied to measure internal damage and crack growth in small mortar cylinders loaded in compression. Synchrotron-based microtomography allows us to reso lve internal features that are only a few microns in size. Multiple tomogra phic scans were made of the same specimen at different levels of deformatio n using a custom-built loading frame. 3D image analysis was used to measure internal crack growth during each deformation increment. Measured load-def ormation curves were used to calculate the nonrecoverable work of the exter nal load on the specimen. Nonrecoverable work of load was related to measur ed incremental change in crack surface area to estimate work-of-fracture in three dimensions. Initial results indicate a nearly constant work-of-fract ure for the early stages of crack growth. These results show that basic fra cture mechanics principles may be applied to concrete in compression; howev er, we must think in terms of 3D multiple crack systems rather than traditi onal 2D single crack systems.