Steady-state deformation of asphalt concrete

Abstract

• An expression has been obtained for the steady-state deformation rate of the asphalt concrete. • The steady-state deformation rate depends on the viscosity, a stress, a temperature and an activation energy. • The graphs for “the steady-state deformation rate – a temperature” are similar. • “The stress substitution principle” has been proposed. • The test for creep is an alternative method for determination of the materials viscosity. The steady-state deformation rate of an asphalt concrete is investigated in details within a wide range of a stress variation (from 0.0081 MPa to 3.0 MPa) and a temperature variation (from + 60 °C to −24 °C). A hot dense fine-grained asphalt concrete of type B accepted for the investigation has been prepared with the use of a road viscous bitumen (4.8 % by weight of a dry mineral material) of the grade 100–130 under penetration. The bitumen was produced by the Pavlodar petrochemical plant (Kazakhstan) by the direct oxidation method from an oil of the Western Siberia (Russian Federation). The investigation of the steady-state deformation of the asphalt concrete has been performed by testing of samples (50x50x150 mm) for creep at direct tension. A load and a temperature have been kept as the constant ones from the beginning to the end of testing of all the samples (241 units). The tests of the asphalt concrete samples for creep have been performed in a device, which has been specially invented and assembled. It has been found out that the tested asphalt concrete is deformed under the impact of a constant stress and at a constant temperature during some period in a steady-state regime, i.e. it is deformed with a constant rate; the dependence of a steady-state deformation rate on a stress is described by power function with a high accuracy at all the considered temperatures; a fundamental expression has been obtained which connects the steady-state deformation rate with its viscosity, stress, temperature and activation energy of the viscous deformation; a simplified expression has been obtained for the steady-state deformation rate of the asphalt concrete for the practical use; a similarity has been shown for the dependence of the steady-state deformation rate on a temperature at various stresses in semi-logarithmic coordinates; “the stress substitution principle” has been formulated. The results obtained in this work have shown that the viscous flow and the steady state deformation (steady-state creep) of the elastoviscoplastic materials as the physical phenomena can be explained on the basis of the kinetic theory of liquids (Ya.I. Frenkel) and the theory of rate processes (H. Eyring). The test for the creep can be considered as an alternative method of the experimental determination for the viscosity of the materials.