EXPERIMENTAL-STUDY OF THE MICROSTRUCTURAL INFLUENCE OF THE STRAIN-SOFTENING BEHAVIOR OF CEMENT MORTAR

The influence of sand grain size on the bridging stress-crack opening displacement curve has been investigated by the Post Fracture Tensile (PFT) testing technique. The PFT method is a well-established techniqu e used in studies of wake-toughened ceramic systems. This method isola tes and characterizes the role of microstructure in the development of closure stresses in the process zone. The critical stress was found t o be higher for the coarse-grained specimen, but there was no influenc e of the sand grain size on the critical crack opening displacement; T he stress-displacement curves, grain size distribution data, and SEM o bservation of the fracture surfaces suggest that the coarse sand grain s are not very efficient in bridging the crack front and consequently give a negligible contribution to the load sharing event in the wake z one. (C) 1998 Elsevier Science Ltd.