Fatigue rheological characterization of polymer-modified bitumens and mastics

Fatigue is one of the major distresses of flexible pavements and is mainly related to the rheological properties of the bituminous components of mixtures. In particular, bitumen and mineral filler create a blend called mastic that significantly influences the service life of asphalt pavements depending on its nature and com- position. The purpose of this study is to investigate the effects of different polymer types and mineral fillers on the rheological behavior of a plain bitumen. Two types of polymer (an elastomer and a plastomer) were employed to produce polymer modified bitumens (PMBs) through laboratory mixing. Moreover, two fillers characterized by a different mineralogical nature (limestone and basalt) were selected in order to obtain several mastics. The dynamic shear rheometer (DSR) was used to study the fatigue behavior of all materials. Experimental data show that the effect of both polymer types is similar on mastics and bitumens as the presence of the elastomer leads to an improvement in fatigue life whereas the presence of the plastomer leads to a slight decrease in fatigue performance with respect to the plain bitumen, regardless of the mineral filler type. Moreover, the stiffening effect of mineral fillers was found to be significant regardless of filler mineralogy and bitumen type leading to a decrease in fatigue life with respect to bitumens. All mastics were less sensitive to the strain level applied as compared to the corresponding bitumens.