THE INFLUENCE OF MICROCRACKING ON THE MECHANICAL-BEHAVIOR OF CEMENT-BASED MATERIALS

Quantitative acoustic emission techniques were applied to basic problems of microfracture in cement based materials. Acoustic emissions in cement based materials result from microcracks and other dynamic phenomena in the fracture process zone. The goals of this research program were to characterize microcracking in various cement based materials, to track the evolution of damage in those materials, and to examine the relationships to overall mechanical behavior. Characterizations of the microcracks showed a dependence on the degree of inhomogeneity in the material. Fine-grained materials showed different microfracture characteristics than coarse-grained materials. Microcracks were characterized according to their fracture mode. The fine-grained materials tested showed primarily mixed-mode microfracture, whereas the coarse-grained materials showed primarily mode II (shear) microfracture. It is experimentally shown that there exists a relationship between the microcrack characteristics established through quantitative acoustic emission analysis and the overall fracture toughness of the material.