Concrete behaviour in direct tension tests at high strain rates

Direct tensile tests on cubic concrete specimens of 60 mm side were performed at strain rates from 1 s⁻¹ to 10 s⁻¹ by means of a modified Hopkinson bar. The results of 26 such high strain rate tests on two concrete types, with 5 and 10 mm maximum aggregate size, are presented in this paper. As reference for these dynamic tests, a series of 14 static tests with specimens of the same geometry was also carried out. The experiments show a significant increase in tensile strength, failure strain, elastic modulus and fracture energy as the strain rates increase. The dynamic results obtained are compared with data and formulations present in the literature, the validity of which is critically assessed. Deviations or knowledge gaps are identified, which confirm the need to generate new data in order to develop more accurate formulae able to predict the evolution of mechanical properties with increasing strain rate.