Rutting and Fatigue Behaviors of Shingle-Modified Asphalt Binders

Abstract

The recycling of asphalt shingles in flexible pavements has received considerable interest in recent years for economic, environmental, and social reasons. The objective of this study was to evaluate the effects of adding ground shingle using the wet process on the binder rutting and fatigue behaviors. The effects of recycled asphalt shingle (RAS) on the binder rutting and fatigue characteristics were investigated using the multiple stress creep recovery (MSCR) and the linear amplitude sweep (LAS), respectively. Further, the influence of adding ground shingle on the binder chemical composition was investigated in the laboratory using the Fourier transform infrared analysis (FTIR) and saturates, aromatics, resins, and asphaltenes (SARA) fraction analysis performed using a thin film chromatography. Based on the results of the experimental program, it was found that the use of RAS in the binder blends was associated with an increase in the percentage recovery and a decrease in the nonrecoverable creep compliance, which indicates an improved resistance to rutting damage. On the other hand, results of the LAS test showed that an increase in RAS content is associated with an improved resistance to fatigue cracking. This is in contradiction to what would be expected, because the asphalt binder in RAS is air-blown, which is extremely stiff and brittle compared to the binder used in roadway applications. Further evaluation of the LAS test with RAS-modified binders is recommended. In addition, analysis of the FTIR spectra showed a slight increase in asphaltenes when RAS was incorporated into the asphalt binder. The increase in asphaltenes was correlated to a slight decrease in maltenes (saturates, aromatics, and resins).