Non-linear behaviour of asphalts in steady and transient shear flow

Abstract

Steady-state and transient shear stress and normal stress data were obtained for four asphalts with a modified Weissenberg Rheogoniometer. Interest was specially related to non-linear behaviour at high shear-rates. The time-temperature superposition principle was found to hold in non-linear behaviour. Moreover, steady-state and transient data could be plotted as master curves irrespective of the nature of the asphalts. In particular, the master curve of steadystate viscosity could be extended to results published in the literature. In the nonlinear region the shear stress relaxation after cessation of a steady shear rate becomes a function of ~ t only and is related to the primary normal-stress coefficient, as predicted by the Yamamoto equation. In the shear stress growth experiment an overshoot is obtained at a constant strain close to 1.5, independent of the rate of strain.

The colloidal structure of bitumen: Consequences on the rheology and on the mechanisms of bitumen modification

“…Attané and co-workers [230] confirmed the construction of master curve as proposed by Shenoy et al and showed that the shearthinning region could be described by a power law behaviour with a typical exponent of −0.5 for the reduced viscosity (i.e., n = 0.5 in the above equation) and an exponent of −1.5 for the first coefficient of normal stresses. In comparison, Sisko found n = 0.7 for three different bitumens [226].…”

“…As described in a former section, measurements of the permanent flow of bitumens under constant shear rate highlight such a critical stress proportional to the viscosity [229,230]. Taking values for micelle size between 2 and 8 nm give calculated σ α ranging from 0.4 to 27 kPa, to be compared to the bitumen-dependent values in the same range measured by Dobson [198], to the almost constant value of 0.3 kPa observed for different materials by Gaskins [190], or to the typical value of 1 kPa found by Cheung [227].…”

Method for Estimating Oil Viscosity via Dielectric Spectroscopy

“…This empirical model relating viscosity and dielectric relaxation time may be used to develop a useful method for estimating viscosity in the field and/or in pipelines. Although previous work exists that attempts to predict viscosity using theoretical rotational diffusion values, temperature-dependent capacitance measurements, or linear diffusion, , to the knowledge of the authors, this is the first time the relationship between dielectric relaxation time and viscosity has been identified. This study concludes that the use of modern impedance analyzers, which are robust and simple to operate, could allow producers of diluted bitumen to meet pipeline viscosity specifications without overdilution.…”