Impact of Crumb Rubber and Other Fillers on the Rheological Properties of Binders
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This paper presents a study to evaluate the rheological properties of crumb rubber modified (CRM) binders and the impact of fillers on such properties. The objective ofthe study was to assess how crumb rubber and sand impact the rheological properties ofthe modified binder systems. The rheological properties were measured according to the Superpave technology and then used to assess the modified binder systems resistance to rutting and fatigue cracking. Two sizes of the crumb rubber (0.18 and 0.425 mm) and one size of sand (2.00 mm) were used with two asphalt binders. The measured rheological properties consisted of the complex shear modulus (G*) and phase angel (o). The data generated from this study led to the evaluation of the impact crumb rubber size, crumb rubber content, and the type of filler on the rutting and fatigue resistance ofmodified binder systems. The analysis of the data proved that by increasing the crumb rubber content, the resistance of the modified binder systems to rutting is increased. However, the impact of crumb rubber content on the fatigue resistance is highly dependent on the type of the asphalt binder. In the case of crumb rubber size, the analysis of the data showed that coarser crumb rubber slightly improves the rutting resistance ofthe modified binder while the impact of crumb rubber size on fatigue resistance is insignificant. When the impact of crumb rubber was compared with the impact of a sand filler, it was concluded that the crumb rubber improves the rutting and fatigue resistance of the modified binder systems as compared to the sand.