Field implementation of WMA mixtures containing recycled asphalt shingles (RAS)

Abstract

Combining Warm Mix Asphalt (WMA) technology with another green technology (asphalt recycling) can lead to a double saving in total cost of asphalt paving production. In this study, field implementation of Hot Mix Asphalt (HMA) with Recycled Asphalt Shingles (RAS) and WMA mixture containing RAS was performed and both mixtures were tested at asphalt laboratory for performance evaluation. To analyze binders and mixtures performance, Fourier-Transform Infrared (FTIR) Spectroscopy test, block cracking test, rutting and moisture resistance (Hamburg Wheel Tracking) test, thermal cracking potential (Disc-Shaped Compacted Tension) test were conducted. A short and medium-term field evaluations were also carried out. Binder extracted from mixtures constructed with and without WMA additive showed the same Performance Grade (PG); however, the extracted binder from WMA mixture was a little softer than the binder extracted from HMA but not enough to bump down the PG grade. Based on sulfur and carbonyl indexes calculated from FTIR test results, WMA mixture found to be more aged. No block cracking was observed in HMA and WMA mixtures by determining G-R values and developing block cracking black space chart. HWT results showed that using WMA technology in asphalt mixtures containing RAS resulted in a relatively better moisture and rutting resistance. The DCT results indicated almost the same fracture energy for both mixtures. The short-term field evaluation after one year of construction showed that the overall condition of both HMA and WMA sections are satisfactory. However, medium-term evaluation (after 39 months) showed more traverse cracks and stripping in WMA mixture.