Abstract
This article presents the results of the viscoelastic properties of the polymer-modified bitumen produced in Warm Mix Asphalt technology. A Fischer-Tropsch synthetic wax and a liquid surface-active agent (fatty amine) were used as bitumen viscosity-reducing modifiers. All tested parameters were determined after short-term and long-term ageing. The complex modulus G* and phase angle δ were measured with a cone-plate rheometer. All dynamic tests were performed at 60 °C within the frequency range from 0.005 Hz to 10 Hz. On the basis of the rheological index R determined using the Christensen−Anderson−Marasteanu (CAM) model, it was found that the fatty amine additive slowed down the age-hardening process in the bitumen. In contrast, the synthetic wax increased the stiffness of the bitumen at all levels tested, regardless of the type of ageing simulation process.
Highlights
Ageing of bituminous binders involves changes in physical and mechanical properties of the bitumen (Judycki & Jaskuła, 2002)
Due to environmental issues and increased environmental awareness creating the need to reduce the impact of production temperatures (140 °C–180 °C), recent years have seen the development of Warm Mix Asphalt (WMA) technologies (Iwański & Mazurek, 2015)
The viscous response of the bitumen modified with a high Fatty Amine (FA) content (0.6%) after ageing is interpreted as the antiageing action of the fatty amines and, as a combined effect of polymer chain degradation and FAinduced softening of the base bitumen
Summary
Ageing of bituminous binders involves changes in physical and mechanical properties of the bitumen (Judycki & Jaskuła, 2002). One of the ways to obtain this effect is to use modifiers acting as binder viscosity reducing agents and allowing aggregate grains to be coated with binders of temperatures lower than those of a conventional hot binder (Iwański & Mazurek, 2011). These modifiers include a FischerTropsch synthetic wax or liquid service-active agents. The CAM model is an attempt to improve the stiffness description of non-modified and modified bitumens It is represented by the following Eq (1) (Li, Zofka, Marasteanu, & Clyne, 2006):. In the bitumen more susceptible to ageing, with a low asphaltene content, the shear modulus will be lower, the relaxation spectrum will be greater and the rate of the relaxation-induced decrease in the values of stiffness modulus will be less rapid (Marasteanu & Anderson, 1999)
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