In-field aging process of high content SBS modified asphalt in porous pavement

Highly modified asphalt (>6.0 wt% styrene butadiene styrene copolymer, SBS) has been extensively used for extending the durability of porous asphalt (PA) pavement. In depth knowledge of the in-field aging of different PA layers is needed because the natural aging of PA possessing around 20% voids content severely affects its properties. The field core samples were taken from sections of the Shanghai Highway which had aged 6 years and 9 years outdoors. The recovered modified binders from different layers (top, middle and bottom) of the PA were evaluated by chemical and rheological characterization. After undergoing outdoors aging, chemical characterization showed that the carbonyl and sulfoxide content of the modified binders had increased for the top layers. The intensities of peaks for bottom layers were lower, demonstrating that the top part of the PA was more exposure to real weather aging. Aging in the degradation of SBS, evaporation of lighter components, oxidation and condensation of the asphalt produces variations in the rheological properties of the recovered binders. Rheological characterization revealed that the highly modified binders continue to perform well even after 6 years and 9 years of outdoor aging.