Unconfined compressive strength is a poor indicator of the high-pressure mechanical response of concrete

Abstract
This paper concerns the concrete behavior under extreme loading situations (ballistic impacts, penetration). During such loadings, concrete material is subjected to very high-intensity triaxial stress states. For the purpose of reproducing such stress levels with well-controlled loading paths, static tests have been conducted on concrete samples using a triaxial press offering very high capacities (stress levels of around 1 GPa). This paper is devoted to experimental results which show that the concrete strength in uniaxial compression after 28 days of ageing, f_c28, is a very poor indicator of the high-pressure mechanical response of concrete. From the composition of a reference ordinary concrete (f_c28 = 29 MPa), two other concretes have been produced with f_c28 equal to 21 MPa and 57 MPa, respectively. Besides, to evaluate the effect of the saturation ratio, Sr, tests have been conducted on both dried samples, wet samples and saturated samples. The results show that contrary to what is observed in simple compression, when placed under high confinement, concrete behaves like a granular stacking. There is no more effect of the cement matrix strength whereas the concrete saturation ratio exerts a major influence.