Effect of strength grade on mechanical properties of concrete under dynamic load

The uniaxial compression test and dynamic compression test of C30, C50, and C80 concrete were carried out. The effects of strength grade and strain rate (epsilon '$$ {\varepsilon}<^>{\prime } $$) on dynamic mechanical properties of concrete were analyzed in terms of dynamic compressive strength, dynamic increase factor (DIF), dynamic peak strain, and dynamic peak toughness. And the strain rate sensitivity of mechanical indexes and DIF fitting model of concrete with different strength grades were explored. The results show that the dynamic compressive strength, DIF and dynamic peak toughness of concrete with different strength grades all have obvious strain rate effects. With the increase of strength grade of concrete, the dynamic peak strain of concrete decreases continuously, and the strain rate sensitivity of dynamic compressive strength and dynamic peak toughness of concrete increases continuously. The mechanical indexes of C80 concrete have the strongest sensitivity to the strain rate. The DIF empirical formula of Comite Euro-International du Beton (CEB) cannot fit the DIF of C30 and C80 concrete effectively. There is a critical strain rate beyond which the strain rate effect of DIF is significantly enhanced. With the increase of strength grade of concrete, the critical strain rate of concrete decreases continuously. The piecewise linear fitting of DIF and lg epsilon '$$ \mathit{\lg}{\varepsilon}<^>{\prime } $$ of concrete with different strength grades shows good results.