Rutting Resistance of Asphalt Mixes Containing Non-Conventional And

Rutting Resistance of Asphalt Mixes Containing Non-conventional and Polymer-Modified Binders C. P. Valkering, D. J. L. Lancon, E. deHilster, and D. A. Stoker

Abstract

In this paper the authors report results of studies on the mechanical stability or rutting resistance of asphalt mixes containing non-conventional binders. Two different types of binders with a reduced temperature susceptibility were investigated: bitumens resulting from a modified manufacturing process, further referred to as multigrade bitumens, and binders obtained by modifying bitumen with a styrene-butadiene-styrene (SBS) copolymer. Multigrade and SBS-modified binders are being examined in two separate projects, the primary objective of which is to increase the mechanical stability of asphaltic mixes in order to combat the effects of the increasing severity of the traffic loading. This paper deals only with the effect of the binders on rut formation, which is a problem at higher service temperatures (>30 deg C). Studies on the performance properties at low temperatures, such as cracking and fretting resistance, which are also influenced by the binder, are in progress. The effect of the binder on the stability of a mix, in terms of the prediction of permanent deformation, can be evaluated in a static creep test. However, the fact that the rheological behavior of, in particular, the SBS- modified binders is different from that of conventional bitumens meant that the creep test had to be modified, which was done by introducing a dynamic loading. The development of this test is discussed and the results obtained on the non-conventional binders are reported. Data on the rut formation under a moving wheel in the Laboratory Test Track (LTT) on asphalt layers with the same binders are also given. The results of the creep and LTT tests represent a quantitative assessment of the effects of the non-conventional multigrade and polymer-modified binders on the rutting resistance of the dense asphaltic concrete wearing course mix used in this study.