Mechanical characterisation of concrete in tension and compression at high strain rate using a modified Hopkinson bar

Reliable material models for concrete behaviour at higher strain rates are necessary for the design and assessment of concrete structures subject to impact and blast. This information should be obtained from experiments performed on large-size concrete specimens (up to 200 mm side cubes) with aggregates of realistic maximum size (16-32 mm). Such type of experiments, based on Hopkinson bar techniques, are conducted and described in this study. Several normal concrete grades and steel-fibre-reinforced concretes have been tested, and full stress-strain curves have been obtained for strain rates up to 10/s. The results, presented in terms of the dynamic increase factor, show clearly the increase of strength of the material with increasing strain rates, more accentuated in tension than in compression, and the influence of the specimen and aggregate size.