Thermorheological Evaluation of Antiaging Behavior of Four Antioxidants in 70/100 Bitumen

Abstract

The rheological properties of bitumen depend on its age state as related to its thermal history. A thermorheological study was conducted by optimizing the amount of antioxidant in combinations using response surface methodology to reduce short-term aging of 70/100 bitumen simulated by a rolling thin-film oven test. A laboratory mixer fitted with a dual helical impeller was used to mix four antioxidants, namely Irganox 1010, Irgafos 168, hydrated lime, and carbon black varying from 1.4% to 11.1% weight for weight (w/w), to come up with synergistic mixture with the lowest aging indices based on comparison with neat 70/100 bitumen. The results of the aging indices were based on change in complex shear modulus as measured by a modular compact rheometer at 58°C and 64°C, and they revealed that combinations of Irganox 1010, hydrated lime, and carbon black gave the lowest aging indices. Synergy and antagony of antioxidant combinations were evaluated based on percentage change in aging. Thermal analysis was used as a screening technique for antioxidant thermal stability within the mixing temperature regime of about 180°C prior application to the 70/100 bitumen.