An image analysis system will be purchased to evaluate various geometrical features of the flaws of portland cement-based composites and to record their interaction preceding macroscopic fracture. An image of a polished section (impregnated with a fluorescent epoxy) will be magnified and digitized using a high resolution video scanner. The digitized image will be enhanced, edited, stored and manipulated to obtain quantitative measures of the flaw structure. This will be done using color TV monitors and a host computer. In addition to quantifying flaw structure and their interactions, fracture toughness measurements will be made and theoretical models relating flaw structure to fracture toughness will be developed. Due consideration to fracture process zone, nonlinear fracture mechanics and crack shielding phenomena will be given. The equipment will enable studies leading to a basic understanding of the influence of flaw structure on fracture properties of cement, mortar, concrete and other cement-based composites.
