Aging effects on the composition and thermal properties of styrene-butadiene-styrene (SBS) modified bitumen

[Display omitted] •Short and long term aging of SBS modified bitumen studied using FTIR, TGA and MDSC.•Thermal stability of bitumen enhanced on addition of SBS.•Long-term aging degrades SBS modified bitumen and induces crosslinking reactions.•Bitumen oxidation induced during blending with SBS.•Specific heat capacity greater for aged SBS modified bitumen blends. The effect of shear rate and mixing time on the composition and thermal properties of unaged and aged bitumen and, SBS modified bitumen was studied using a combination of Fourier Transform Infrared (FTIR) spectroscopy, Modulated Differential Scanning Calorimetry (MDSC) and Thermo-gravimetric Analysis (TGA). The increase in intensity of IR absorbance bands for carbonyl, sulfoxide and aromatic functional groups can be correlated with the oxidation of bitumen as, a consequence of processing, as well as for simulated long-term aging. Modification of bitumen with 5 wt% SBS enhanced the thermal stability of bitumen, altered the mechanism of degradation from a single process to one with three steps and resulted in increases (to 85 °C) in the onset temperature of degradation of aged samples. Irrespective of whether the samples were aged or not, the specific heat capacity (Cp) of the blends, determined from MDSC measurements, increased with increasing shear rate and mixing time, but all Cp values were greater for aged samples. The application of heat and pressure in simulated long-term aging alters the structure of SBS modified bitumen blends via degradation and crosslinking reactions manifest by changes in the glass transition temperature (Tg) of the bitumen components, as measured by MDSC.