Viscoplastic properties of asphaltic bitumen

Abstract

In the present paper, various relationships between stress and strain rate have been derived. They are interpreted by rheological models, which may express the mechanical behaviour of the tested material. The experimental curves are compared with theoretical relationships corresponding to various presented rheological models. From these models, the theoretical rheological equations have been derived, which may express the behaviour of bitumens exhibiting viscous and plastic properties. Some experimental curves are evaluated by the procedure of least squares and the empirical equations of the first and second degree between stress and strain rate are found. These equations contain the equilibrated yield stresses, the coefficient of viscosity and the second-order coefficient of viscosity. The influence of temperature on various samples has been observed. In the most general case, the bitumen exhibits viscous and plastic properties, which may be represented by rheological models consisting of viscous and plastic elements. The paper deals with the theoretical and experimental investigation of the rheological behaviour of the asphaltic bitumen. The results of rheological tests are evaluated by the procedure of least squares and various empirical equations between shear stress and shear-strain rate are found. The experimental curves are compared with theoretical relationships derived on base of rheological models consisting of many groups of plastic and viscous elements.