Experimental Investigation of the Confined Behavior of Dry and Wet High-Strength Concrete: Quasi Static Versus Dynamic Loading

Abstract

This paper presents an experimental investigation of the behavior of high-strength concrete (fc28 = 80 MPa) under very high pressure and quasi-static and dynamic loadings. Concrete specimen is inserted in an elastic, high-strength steel ring and subjected to an axial compression. In order to evaluate the confining pressure acting on concrete the ring is instrumented with multiple hoop strain gauges glued on its outer lateral surface. Dry and wet specimens are tested in both static and dynamic loadings in order to assess the influence of the free water content and the strain rate. Dynamic test are performed with a large diameter (80 mm) split Hopkinson pressure bar facility, adapted to test samples of large size (required for testing concrete material) at high stress levels. A strong effect of the free water content and the strain rate is observed in both deviatoric and volumetric behaviors of high-strength concrete. Both, the shear strength and volumetric stiffness increase with the increase of loading rate. One the other hand, free water has a beneficial effect on the volumetric stiffness and a strong negative influence on the deviatoric strength of high-strength concrete. The behavior of high-strength concrete was also compared to that of an ordinary concrete (fc28 = 30 MPa), tested in a similar experimental campaign. In both static and dynamic conditions, dry specimens of the two concretes reach approximately the same deviatoric stress level. However, when the specimens are saturated with free water, high-strength concrete exhibits a deviatoric strength much greater than ordinary concrete.