The Effect of Asphalt Binder Aging on Fatigue Performance of Evotherm WMA

One of the main benefits advertised with the use of warm mix asphalt (WMA) is the decreasing aging of the asphalt binder resulting from the lower production temperature compared to conventional hot mix asphalt (HMA). Some tests were performed to determine the asphalt binder aging properties from WMA and HMA. Asphalt binders were recovered by extraction and distillation from asphalt mixtures premixed at different temperatures (140 degrees C, 160 degrees C, 180 degrees C for HMA, 100 degrees C and 120 degrees C for WMA) in the mixing plant. Penetration@25 degrees C, softening point (R&B) and rotational Brookfield viscosity tests were carried out. Results show that the aging of asphalt binder increases as the mixing temperature is elevated, and remarkably accelerates at the temperatures higher than 150 degrees C. Warm mix asphalt (for example, mixing temperature at 100 degrees C or 120 degrees C) can greatly reduce the aging of asphalt. Aging of the asphalt binder is one of the factors that would affect the mixture's fatigue life. Four-point beam fatigue test samples were mixed and compacted at 140 degrees C for HMA and 120 degrees C for WMA, and fatigue tests with a frequency of 10 Hz and three constant strain levels (150 micro-strain, 300 micro-strain, 450 micro-strain, respectively) were performed. Results show that WMA's fatigue life was higher than the control HMA, which indicates that it may reduce aging of asphalt binder and improve fatigue performance of asphalt mixture at lower production temperatures.