Modelling the Significance of a Rubber Sleeve on the Indirect Tensile Strength of Concrete

This paper seeks to numerically simulate and verify laboratory experimental results of concrete disk specimens undergoing indirect (Brazilian) tension testing with a circumferential rubber sleeve. The objective of using the rubber sleeve was to allow for the measuring of air permeability as damage accumulates during the Brazilian disk test. Preliminary experimental observations indicated a reduction in the load strength when the rubber sleeve exists around the specimen. A numerical tool based on the combined finite-discrete element method is used to verify this behavior of concrete in 3D and explain the reason for the strength reduction. Sleeved and un-sleeved specimens were modeled with boundary conditions matching those produced experimentally. The numerical model was able to effectively capture crack propagation and the strength range observed in the experiments. It is apparent that the bond strength of the rubber sleeve with concrete creates additional lateral displacement and tensile stresses during loading resulting in reduced concrete strength. The simulation shows the possible use of the finite-discrete element code to explain details of the mechanical behavior of concrete and quasi-brittle rocks.