Characteristic properties of asphalts with elastomer-modified bitumen

2 Characteristic properties of asphalts with elastomer-modified bitumen 

The asphalts (bituminous mixtures) produced with elastomer-modified bitumen have, above all, improved elastic properties. As a result, the asphalt layer with elastomer-modified bitumen has better permanent deformation and fatigue performance when compared to the asphalt layer with conventional bitumen. 

Dynamic and static stiffness moduli of the asphalt with modified bitumen also increase in comparison to the asphalts with conventional bitumen. However, the latter does not constitute the most characteristic changes in asphalts produced with SBS-modified bitumen. 

Permanent deformation behaviour of asphalts is determined by the wheel tracking test (see Sections 7.6.5 and 7.6.6). From an extensive study, it was found that the wheel tracking parameters such as rate or the wheel tracking slope and the rut depth or the proportional rut depth of the asphalt concrete mixtures (AC 20 mm) with SBS-modified bitumen were, in all cases, lower than those obtained for the AC 20 mm mixtures with 50/70 grade bitumen (Nikolaides and Manthos 2009). 

Finally, the use of elastomer bitumen increases Marshall stability, but it may also increase the Marshall flow above the limiting value. This increase cannot be taken as a drawback, since the nature of the test is such that it does not take into account the recovered (elastic) deformation during unloading and in effect does not simulate dynamic loading. Regarding the optimum binder content of the asphalt with or without modified bitumen, it was found that, when asphalt concrete mixtures were tested, the optimum binder content as determined by the Marshall procedure was not significantly different (Nikolaides and Tsochos 1992). 

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