FTIR spectroscopy analysis assessment of reclaimed asphalt at asphalt mixing plants to optimize the recycling

Reclaimed asphalt pavements (RA) usually are fully recyclable in new asphalt mixtures. The properties of the individually aged and possibly modified bitumen in the RA will affect the mix design of the new asphalt mixture. Furthermore, the RA may contain hazardous PAH-contamination resulting from coal tar, which was applied in German road pavements up to the 1980′s. For identifying substances that impair or influence reusability of the RA the Fourier transform infrared spectroscopy (FTIR) method was modified. Within a total measuring time of approx. 20 min, the binder contained in a sample of granulated road construction material can be recovered by means of a rapid extraction and measured by FTIR-ATR. By evaluating the measured absorption spectra, samples which have to be considered as PAH-contaminated (with PAH contents ≥ 25 mg/kg) could be distinguished from non-contaminated reclaimed asphalt. Furthermore, the presence of styrene-butadiene-styrene (SBS) modification as well as viscosity-changing organic additives could be identified.