Effect of the laboratory short-term aging temperature on the chemical and rheological characteristics of high modulus asphalts

Abstract

Rolling thin film oven (RTFO) has been widely used to simulate the short-term aging of base asphalt. However, owing to that the high-viscosity and high-modulus asphalt binder (HMAB) generally requires a higher temperature to disperse in the aging bottle, there are some doubts about the applicability of the current RTFO aging temperature in the simulation of aging of HMAB. In this paper, the base binder (K64) was added with 8%, 12%, 16%, and 20% Xinjiang rock asphalt (XRA) and 20%, 30%, 40%, and 50% Button rock asphalt (BRA) by weight respectively to prepare HMAB. The RTFO and modified RTFO (MRTFO) tests were performed at various temperature (163, 178, and 193 °C) to simulate the short-term aging of HMAB. The classes for properties of the HMAB prepared in the laboratory and a commercial HMAB were determined based on the conventional physical properties, performance grade (PG), and rotation viscosity tests. Further, the frequency sweep, multiple stress creep and recovery (MSCR), and Fourier transform infrared (FTIR) tests were employed to characterize the effect of aging temperatures on the rheological and chemical properties of HMAB, respectively. The classes for properties of HMAB suggested that the modified asphalt met the HMAB standard when the addition ratios of XRA and BRA were higher than 12% and 30% by weight of the K64, respectively. The FTIR results indicated that the carbonyl jump growth could be detected for every HMAB when the aging temperature was raised to a certain level, and the temperature of carbonyl jump occurred in MRTFO was 15 °C lower than that of RTFO. The rheological test results implied that the significant changes in complex modulus, phase angle, nonrecoverable creep compliance (Jnr), and percent recovery (R) were observed at the aging temperature where carbonyl jump occurred. The RTFO aging temperature for 20HX, 50HB, and 7.5S could be roughly determined as 178 °C, 178 °C, and 193 °C based on carbonyl jump and equal aging effect between MRTFO and RTFO occurrences.