AGING SUSCEPTIBILITY AND PERFORMANCE OF OIL MODIFIED ASPHALT BINDERS
MetadataShow full item record
As oils are becoming more popular additives in asphalt binders as low temperature modifiers, there has been interest in the performance, especially the long-term aging, of oil modified asphalts. Research studies have reported widely varying effects of different types of oils on asphalt binders in terms of rheological and aging properties. This thesis is focused on characterizing the aging susceptibility or oxidation potential of commonly used oils to determine if the susceptibility is related to observed aging susceptibility of asphalt binders modified with oil and polymers. To accomplish this, two common oils, bio-oil and re-recycled engine oil bottoms (REOB), were aged in the PAV for several different intervals and then tested in a dynamic shear rheometer to detect changes in complex shear modulus and phase angle. Aging indices were calculated to normalize the magnitudes of change. Then 6 blends were prepared using bio-oil and REOB with combinations of polymers including SBS, Elvaloy, and PPA. Each oil was combined with each polymer combination to meet similar low-temperature performance grades. Two control blends, one containing SBS, the other a refinery produced PG 58-34 using an unknown quantity of Elvaloy, were prepared and obtained, respectively. Extended PAV aging was performed for 20-, 40-, and 60-hour cycles. Blends were then tested using frequency sweeps, elastic recovery tests, bending beam rheometer testing, and bitumen bond strength testing to evaluate the aging susceptibility on various performance metrics at different temperature levels. Results show that bio-oil exhibits nonlinear and high aging susceptibility while the REOB exhibits no appreciable susceptibility to aging in terms of its complex shear modulus aging index and phase angle aging index. Testing of the modified asphalt blends yielded performance results that varied based on not only the aging susceptibility of the oil itself, but also of the polymer additives, as well as the interaction of the oil with the polymer. Blends containing the bio-oil performed better in the low temperature testing as compared to the blends with REOB, but the REOB blends showed better aging susceptibility results when measured at intermediate temperatures. Analysis of the results leads to conclude that aging of blends cannot be predicted from the aging of the oils, and there are significant interactions with polymers. Therefore, extended PAV aging is required to accurately define the long-term aging effects of these oil modifiers.