An improved experimental technique for dynamic direct tensile testing of concrete

Abstract

Dynamic tensile testing of concrete materials has been proven to be extremely challenging due to their heterogeneity, low tensile strength, and brittleness. The present study introduced an improved experimental technique for the testing of cementitious materials under dynamic direct tensile loading on a Kolsky tension bar. This technique involves using a pair of aluminum adapters attached to the bars, with the concrete specimen secured to these adapters by epoxy adhesive. As a result, specimen detachment and cleaning after the test become much more efficient. However, the proposed technique also presents challenges caused by the inertia forces from the mass of adapters as well as the overestimation of the specimen strain due to the deformation of adapters. These challenges were addressed by modifications to the conventional approach of data post-processing in Kolsky bar experiments. In addition, pulse shaping techniques were utilized to develop an optimal loading wave, thereby enabling the attainment of valid testing conditions. The proposed technique was evaluated through the testing of a steel microfiber reinforced concrete. Our results have demonstrated for the very first time that dynamic stress equilibrium and constant strain rate deformation can be achieved to evaluate concrete on a Kolsky direct tension bar through careful experimental design.