Measurement of fracture properties of concrete at high strain rates

Abstract

An analysis of the spalling technique of concrete bars
using the modified Hopkinson bar was carried out. A
new experimental configuration is proposed adding
some variations to previous works. An increased
length for concrete specimens was chosen and finiteelement
analysis was used for designing a conic
projectile to obtain a suitable triangular impulse
wave. The aim of this initial work is to establish
an experimental framework which allows a simple
and direct analysis of concrete subjected to high
strain rates. The efforts and configuration of these
primary tests, as well as the selected geometry and
dimensions for the different elements, have been
focused to achieve a simple way of identifying the
fracture position and so the tensile strength of tested
specimens. This dynamic tensile strength can be easily
compared with previous values published in literature
giving an idea of the accuracy of the method and
technique proposed and the possibility to extend it in a
near future to obtain othermechanical properties such
as the fracture energy. The tests were instrumented
with strain gauges, accelerometers and high-speed
camera in order to validate the results by different
ways. Results of the dynamic tensile strength of the
tested concrete are presented.
This article is part of the themed issue ‘Experimental
testing and modelling of brittle materials at high
strain-rates’.