Emission analysis of recycled tire rubber modified asphalt in hot and warm mix conditions

The hazardous emissions of crumb rubber (CR) modified asphalt during construction has been a concern for a long period. This study aims to identify the emission components in the CR modified asphalt in traditional hot mix asphalt (HMA) and with recently developed warm mix asphalt (WMA). The dynamic headspace gas chromatography-mass spectrometry (GC-MS) was employed for identifying the emission of asphalt binders at 120 degrees C, 140 degrees C and 160 degrees C. The coupling of gas chromatography and Fourier-transform infrared spectroscopy (GC-FTIR) was used to analyze the emission during the plant mixing for conventional HMA, CR-HMA and CR-WMA. The results showed the emission amount was highly dependent on mixing temperature. The warm mix technology can reduce the emission level significantly and should be encouraged in the asphalt mixture containing CR. Asphalt source and other extra additives in producing CR modified asphalt can also affect the emission significantly. Asphalt mixture containing CR can release toxic emissions such as xylene and toluene significantly higher compared to that without CR. In addition, it was found that the emission amount from the GC-MS test for asphalt binder was lower than that in the field test for asphalt mix due to the thin asphalt film of asphalt mix.