ABSTRACT
A series of thick-walled hollow cylinder tests are being performed on a weak mortar as part of an investigation concerning the size effect in weak quasi-brittle materials subject to multiaxial compressive stress. In this paper, we present test results for scaled hollow-cylinders tested under hydrostatic external stress while the inner-hole pressure is kept equal to atmospheric. A constant length/outer-/inner-diameter ratio of 6/4/1 respectively is maintained in all tests with a scale range 1:8. Radial deformations at the inner-wall are recorded during testing and the failed zone around the model holes is carefully preserved after testing using vacuum impregnation techniques with a fluorescent-epoxy resin. A size effect has been observed with respect to the external hydrostatic stress needed to initiate failure. In addition, at a loading stage close to failure, fine micro-cracks develop around the inner-hole oriented parallel to the inner-wall in a concentric pattern.
