Properties of Modified Bitumen Obtained from Vacuum Bottom by Adding Recycled Waste Polymers and Natural Bitumen

Post-consumer waste polymers are considered as environmental pollutants that should be reused as inexpensive materials. Also, there are resources of natural bitumen in several regions of Iran that can be used to modify bitumen. The purpose of this study is to investigate the possibility of obtaining penetration grade modified bitumen from vacuum bottom residue (VB) by adding various recycled waste polymers and non-polymer materials without air blowing VB. Following this concept, natural bitumen (NB), recycled waste polyethylene (PE), recycled waste latex, crump rubber modifier (CRM) and heavy vacuum slopes (HVS) were used. The formulation of mixing blends was determined by experimental design method using design-expert V.7.16 software. It was found that 40/50, 60/70 and 85/100 grades of penetration bitumen with improved performance grades, 82-40, 70-40 and 70-40, respectively, are producible using these materials, although, decreased ductility is observed almost for all the blends. A combination of 10% natural bitumen and 5% recycled latex with VB are considered as the best blend amongst all blends. The resulting modified 60/70 grade bitumen shows improved complex modulus in comparison with neat 60/70 bitumen and consequently it has increased resistance against permanent deformation (rutting). Also, the lowered Frass breaking point of this blend (-21°C) improved its low temperature performance (PG = 70-40). Unfortunately, when the crump rubber modifier particles are not well-dispersed and fine enough in bitumen matrix, there is an unexpected decreased ductility occurred in the blends.