Rheology and structure of mixtures of road tar and bitumen

Abstract

Discontinuities previously observed in the softening point and insoluble matter curves of tar‐bitumen systems have been investigated by carrying out a number of flow tests and viscosity measurements over a wide temperature range. The results provide evidence that stable mixtures comprising up to 60% bitumen are thixotropic at and below the softening temperature, due possibly to a marked association of certain tar components. With bitumen in greater excess the higher‐molecular‐weight hydrocarbons and oxygen‐containing compounds of the tar are pepsised by the bitumen. It is suggested that phase inversion occurs at a composition of about 50% by volume of each component.