The oedometric EOS of equal strength and different mix compositions concrete specimens

Abstract

The uniaxial compressive strength of concrete is commonly used to characterize concrete properties. The three-dimensional behavior of concrete structures is modelled by the hydrostatic and deviatoric relationships. These relationships are assigned to a given concrete according to its uniaxial compressive strength. Based on high velocity penetration test results at targets with identical concrete strength, that were prepared from different mix designs, the authors conjectured that the slab behavior is not governed by the uniaxial compressive strength but by the concrete composition.This paper presents an experimental investigation of concrete specimens of equal uniaxial compressive strength, that are made from different mix compositions, aiming at examining the equation of state (EOS) and its relationship to the uniaxial compressive strength and to several mix components, in attempt to validate the above conjecture.A set of specimens was prepared characterized by equal uniaxial compressive strength (fc = 56 MPa) measured on 100 mm sided cubes. Several specimen groups were tested, each of them made from a different composition. The mix variables were the weight of water (and the corresponding weight of cement), the aggregates weight and the maximum aggregate size. The specimens were tested in a special triaxial apparatus, to high load-levels (up to 5000 kN), at a quasi-static rate of ∼ 5 kN/sec. Test results show a wide scatter of the EOS curves, depending on the different mix parameters. These results refute the commonly assumed correlation between the uniaxial compression strength and the EOS and validates the conjecture that the EOS depends on the specific concrete mix composition.