Influence of Free Water and Strain-Rate on the Behaviour of Concrete Under High Confining Pressure

Abstract

Concrete structures can be exposed to dynamic loadings such as detonation near a concrete structural element or projectile-impact. Such loadings lead to intense damage modes such as mode II fracturing and collapse of pore resulting from shear deformation and high confining pressures. To investigate the dynamic response of concrete under high levels of pressure, quasi-oedometric compression tests have been performed with a Split Hopkinson Pressure Bar facility. The concrete sample is placed within a confining ring and compressed along its axial direction. The swelling of the sample induces an increase of the contact pressure at the ring-sample interface leading to hydrostatic pressures as high as 800 MPa and axial strain about −10 %. The radial stress is deduced from strain gages glued on the metallic vessel and the axial stresses is derived from a classical Kolsky processing so the deviatoric strength and volumetric strain are obtained as function of the level of hydrostatic pressure. Finally, the quasi-static and dynamic experiments performed with water-saturated specimens or dry samples allow assessing the influence of water content and strain-rate on the confined behaviour of concrete.