Influence of commercial waxes on bitumen aging properties

Aging properties of wax-modified 160/220 bitumens and the influence of wax on these properties were evaluated using dynamic mechanical analysis (DMA), bending beam rheometer (BBR) analysis, force ductility testing, Fourier transform infrared (FTIR) spectroscopy, and thin-layer chromatography (TLC-FID). The binders were aged by means of the rolling thin-film oven test (RTFOT) and a pressure aging vessel (PAV). It was observed that aging resulted in oxidation of the bitumen (increase in carbonyl absorbance and in resin and/or asphaltene content by TLC-FID.) Changes in rheological properties of aged wax-modified binders depended on the base bitumen as well as on the type and amount of wax additive. Aging increased the complex modulus as well as elasticity, indicated by a decrease in phase angle at medium temperatures. For the polyethylene wax (PW)-modified binders, originally showing a large decrease in phase angle at higher temperature, this decrease was markedly reduced by aging, indicating network damage. Results and aging indexes obtained in this study indicate no or marginally positive influence of wax on bitumen aging properties.