Thermal Decomposition Characteristics of In‐Service Road Asphalt Mixtures Under Air/Nitrogen Atmosphere

The pyrolysis reaction process and pyrolysis characteristics of asphalt mixtures were investigated using thermogravimetric‐Fourier transform infrared spectroscopy‐gas chromatography/mass spectrometry (TG–FTIR–GC/MS). The results indicate that three weight loss peaks can be found in the asphalt mixture under air atmosphere, while two weight loss peaks appear under N 2 atmosphere. The pyrolysis mechanism function of asphalt mixture under air atmosphere is transformed from order reaction ( F 6) to phase boundary reaction ( R 3). However, the mechanism function under N 2 atmosphere is F 1 order reaction. The FTIR spectrum shows that the main gas products under different atmospheres are similar, including CO 2 , gaseous H 2 O, and C=O functional group vibration products. The GC/MS data imply that 15 abundant products are generated under air atmosphere, while five products are detected under N 2 atmosphere.