Experimental study on the size effect on the equation of state of concretes under shock loading

Adopting the classical theory of hydrocodes, the constitutive relations of concretes are separated into an equation of state (EoS) which describes the volumetric behavior of concrete material and a strength model which depicts the shear properties of concrete. The experiments on the EoS of concrete is always challenging due to the technical difficulties and equipment limitations, especially for the specimen size effect on the EoS. Although some researchers investigate the shock properties of concretes by fly-plate impact tests, the specimens used in their tests are usually in one size. In this paper, the fly-plate impact tests on concrete specimens with different sizes are performed to investigate the size effect on the shock properties of concrete materials. The mechanical background of the size effect on the shock properties are revealed, which is related to the lateral rarefaction effect and the deviatoric stress produced in the specimen. According to the tests results, the modified EoS considering the size effect on the shock properties of concrete are proposed, which the bulk modulus of concrete is unpredicted by up to 20% if size effects are not accounted for.