Some Aspects of Experimental Techniques

Abstract

The first lecture, entitled “On the Cracking in Concrete and Fiber Reinforced Concrete” was presented in two parts. The first part, given by S. Diamond, focused on the observations of cracking patterns in cement paste, mortar and concrete through a scanning electron microscope (SEM). The limits of previous studies with optical microscopy were apparent from the finding that the higher resolution provided by SEM allowed to detect the presence of cracks having a width of fractions of a μm. The tortuosity of the crack path, the existence of branching, the regions of fine multiple cracking near the ends of each branch were documented by micrographs of different magnification. The second part, given by A. Bentur, illustrated the results obtained for fiber reinforced cement composites. The different types of cracking patterns at the intersection of a propagating crack and a fiber were illustrated. The complexity of the debonding phenomenon and its dependence on the type of fibers appeared clearly by the use of a specially designed specimen.