Use of Surface Activated Recycled Waste Polypropylene in Bitumen Modification

Bitumen polymer modification has a long history. However, most of the polymers currently used as additive in bitumen are not economically attractive. Thus, employing recycled materials in flexible highway instead of virgin ones has become a fundamental case for researchers especially in terms of cost efficiency and environmental awareness. To date, many studies have been made to investigate using of recycled polymers in bitumen and generally improved physical properties of bitumen were determined. In this study, the recycled polypropylene (PP) was investigated for bitumen modification. Surfaces of recycled polypropylene (PP) waste will be activated by chemical method that has never been processed before in Turkey. Free radicals, ions and functional groups will be formed on the surfaces of surface-activated polypropylene and thus homogenous binders having strong bonds were obtained by allowing them to have a chemical reaction with bitumen.   The compatibility surface-activated PP admixtures with bitumen and the morphologic structure of the modified bitumen was investigated with the help of FTIR spectroscopy. Conventional test methods such as, penetration, softening point and ductility tests were also performed on base and PP modified bitumen samples. In order to determine effects of surface-activated waste PP on aging properties of bitumen, rolling thin film oven test (RTFOT) was performed on to all binders. After determining the fluidity characteristics of base and PP modified bitumen at high temperatures (135oC) with rotational viscosity (RV) test, the rutting resistance (complex shear modulus, G* and phase angle, δ) of aged binders under certain temperature and loading conditions were investigated by dynamic shear rheometer test (DSR). The tests results reveal that a gradually increment in PP modification leads to a decrease in penetration and an increase in softening point which is evidence of an increased stiffness of bitumen. An increment in rutting parameter after modification observed by DSR test is a clear indication of better rheological properties of bitumen which means permanent deformation occurred in flexible pavement can be restrained by surface-activated waste polypropylene modification.