Document Type : Research Paper
Department of Chemical Engineering, Islamic Azad University of Ilkhchi Branch, Tabriz, Iran
Chemical Engineering Department of Chemical Engineering , Faculty of Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran
Owing to climate conditions, heavy traffic loads, and increasing axial loads, conventional bitumen/asphalt should be modified. Bituminous materials are also vulnerable to aging during construction and service time of pavement, which will seriously affect the service performance/life of bitumen pavement. To this end, bitumen was modified using styrene-butadiene-styrene (SBS), ZnO, TiO2 and ethylene vinylacelate (EVA). Applied methodology was Mixture Design and contents of SBS, ZnO, TiO2 and EVA were considered as independent variables. Response variables followed as: G*/sin OB, G*/sin RTFO, G*/sin PAV, RV, penetration (PEN), softening, ductility, m-value and stiffness. Results of experiments of penetration degree, softening point, and ductility performed on basic bitumen without any additives were 89, 49 °C, and 137, respectively. Effects of independent variables were investigated on response variables using mathematic models and optimized compositions. SBS, ZnO, TiO2 and EVA precursors positively affected the PEN parameter. Manipulated samples possessed penetration range of 48–62 (1/10mm). Maximum softening was reached at the highest EVA and the minimum softening was detected at the largest ZnO and TiO2. Softening point ranged in 59–71 °C. SBS, ZnO, TiO2 and EVA components positively increased ductility and the largest positive effect belonged to SBS. SBS and EVA positively affected G*/sin OB response, whereas ZnO and TiO2 variables negatively decreased it. Dynamic shear rheometric (DSR) data for aged bitumens within short term periods decreased from 52 to 76 °C for all investigated samples. All mentioned modifications were performed to optimize performance of ultimate bitumen from perspectives of softening, ductility, strength, m-value, stiffness, etc.