Fracture mechanics modeling using images of fracture surfaces

The fracture surface is important evidence of the behavior of cement-based materials. Deflection, microcracking, and bridging are mechanisms that occur at the crack tip and absorb energy during the fracture process. Two optical microscopy techniques are used in this study to characterize surface geometry. The confocal laser microscope and a video density technique that uses video microscopy provide elevation data for the mesoscale of mortar and concrete. Recently, surface maps have been used to establish a link between surface roughness and fracture. In this paper, the tortuosity of the fracture surface is used in a micromechanical model to predict the increase in toughness due to aggregate. This analysis is performed for two sets of mortar specimens to investigate the influence of the aggregate size and gradation. The influence of crack deflection and aggregate fracture is compared to tested fracture parameters. (C) 1998 Elsevier Science Ltd. All rights reserved.