The Rheological Properties of Bitumen Emulsions

ABSTRACT This article is the first of a series of two that presents a comparison between the rheological properties of bitumen emulsions as measured either by means of efflux time viscometers (NF T66-020 and prEN 12846) or by more fundamental methods using a constant-rate rheometer. In this first part, the basic theory behind efflux time measurements is derived as a function of the rheological properties of the emulsions, assuming first Newtonian behaviour and then a more realistic Casson-type behaviour. Kinetic energy corrections in both cases are included. Thus, it is shown how the yield stress behaviour of bitumen emulsions, to be described more thoroughly in Part II of this series of articles using a Casson law, need to be taken into account in order to accurately describe efflux times measured with conventional devices such as the Engler or STV viscometers (NF T66-020—prEN 12846).