Fatigue and Healing Characteristics of WMA–RA Blended Binders

Abstract

Asphalt mixes prepared using warm-mix asphalt (WMA) technology have similar capabilities to hot-mix asphalt (HMA) mixes for reducing emissions and energy consumption along with on-par performance. Recycled asphalt (RA) mixtures exhibit superior resistance to rutting and moisture damage due to the presence of stiff aged binder, which also has negative impact on fatigue resistance. The chemical composition and flow characteristics of asphalt binders govern their ability to heal and recover from fatigue damage when subjected to rest periods and/or suitable temperatures. Fatigue and healing characteristics of WMA–RA blends were evaluated by conducting linear amplitude sweep and time sweep tests using dynamic shear rheometer. It was observed that fatigue resistance of the WMA binders improved with addition of the reclaimed asphalt pavement (RAP) binder. The influence of rest period on healing was determined by analyzing the slopes of the fatigue life versus rest period plots. It was observed that the fatigue lives of the binder increased with rest periods due to damage recovery, and the healing ability decreased with RAP binder increments. In addition, correlations were established between healing potential and various rheological and chemical composition. The healing potential of WMA–RA showed strong correlation with rheological and chemical composition including G*sinδ, surface free energy, and aging indices computed using Fourier transform infrared spectroscopy. Fatigue resistance results from two opposing phenomena: crack formation and crack healing. The fatigue performance of asphalt binders was evaluated using conventional tests such as superpave fatigue parameter (G*sinδ) from oscillation test and linear amplitude sweep. However, these tests do not account for rest periods present in real-time traffic load application. Therefore, a time sweep test protocol with intermittent loading patterns was adopted by introducing rest periods to simulate real traffic conditions. Healing indices for all binder blends were estimated by analyzing the slope of log of fatigue life versus log of rest periods. Further, correlations were developed between the fatigue and healing characteristics with chemical characteristics of binders evaluated using surface free energy (SFE) and Fourier transform infrared (FTIR) spectroscopy tests. This multifaceted approach aids civil engineers and highway agencies in understanding the interactions among different factors affecting binder performance. By analyzing these correlations, the study identifies key factors significantly impacting the fatigue and healing performance of warm-mix asphalt–recycled asphalt (WMA–RA) binders. The developed correlations suggest that SFE or FTIR aging indices can be used as indicators for fatigue and healing performance, eliminating the need for exhaustive fatigue and healing tests, thus saving significant time and resources.