Viscoelastic properties of bitumens in continuous and cyclic deformation

Abstract

Viscoelastic properties of bitumens have been investigated under cyclic and continuous shear deformation and under the joint effect of both types of deformation. The experimental results indicate a similarity between the viscoelastic behaviour of bitumens and polymer systems. It is shown that for the bitumens studied the curves of the loss modulus against frequency in the linear region, and of the shear stress against the shear rate, coincide. Relaxation spectra of bitumens have been constructed, which point to a relaxation-time distribution more complicated than theGaussian distribution. It has been established that cyclic deformation with large amplitudes causes the truncation of the low-frequency portion of the curves of the storage and loss moduli against frequency, which is higher, the greater the deformation rate amplitude. The dependence of the absolute value of the complex viscosity on the deformation rate amplitude, in the range of large amplitudes, is symbatic to the dependence of the apparent viscosity on the shear rate. The deformation rate amplitude, however, affects the absolute value of the complex viscosity and the apparent viscosity in different ways.