Size effect on dynamic tensile characteristics of concrete subjected to high loading rate

Present study explores loading rate and specimen size influence the dynamic tensile behaviour of concrete grades (M35 and M60) using split Hopkinson Pressure Bar apparatus. The dynamic splitting tensile strength of standard concrete increases from 10.43 to 18.56 MPa as the loading rate rises from 130.3 to 412.3 GPa.s^-1. Similarly, for high strength concrete, dynamic splitting tensile strength increases from 12.0 to 19.86 MPa with loading rates from 214.5 to 492.9 GPa.s^-1. Larger specimens demonstrating higher rate sensitivity showed higher and dynamic increase factor due to lateral inertia and crack propagation. The quasi-static size effect law was modified for dynamic loading conditions and critical stress rate were obtained as 59.2 and 88.8 GPa.s^-1 for standard and high strength concrete, respectively. The modified dynamic increase factor model of CEB-FIP considering strain rate and size effect simultaneously strongly supported the experimental dynamic increase factor values with an ±13% deviations. The splitting tensile strength of standard and high strength concrete calculated using the modified equation of rock brittle materials, shows a percentage deviation within ±10% of the actual experimental values.