Fracture mechanics modeling with fracture surface image data

The fracture surface of mortars and concretes is important evidence of the behavior of these materials. Deflection, microcracking and bridging are mechanisms presumed to be taking place at the crack tip. Through two optical techniques, the surface geometry can be obtained digitally in the form of topographic maps. The confocal laser microscope and a video density technique provide elevation data for the mesoscale of mortar and macroscale of concrete. Recently, the surface maps have been used to establish a link between surface roughness and fracture parameters, as well as to investigate the fractal nature of these materials. The tortuosity of the crack can be used in a micromechanical model to predict the increase in toughness due to the aggregate. The deflection angle of the crack in the direction of propagation as well as perpendicular to it is used to determine the local strain energy release rate for the mixed mode condition at the crack tip. This analysis is performed for two sets of mortar bars to investigate the influence of the aggregate. One set varies the maximum aggregate size of the sand distribution, while the other has mono-sized aggregate of varying diameters. The influence of crack deflection and aggregate fracture will be compared to tested fracture parameters.