Effects of temperature and age on stress relaxation in straight and modified asphalt binders from a northern Ontario pavement trial

Abstract

The effects of temperature and age on stress relaxation were investigated for a set of seven asphalt binders from a northern Ontario pavement trial. It was found that between binders, there were rather wide variations for different modes of relaxation. The first peak in the relaxation spectrum, originating from the rapid relaxation within the mobile saturates domains, was relatively insensitive to ageing. The second and third peaks at higher relaxation times changed more with both laboratory ageing and temperature changes. The straight-run Cold Lake asphalt binder showed the least amount of change, and this can likely explain its superior field performance. High styrene–butadiene (SB and SBS) polymer loadings, the presence of polyphosphoric acid (PPA), or re-refined engine oil bottoms (REOB) all resulted in solid-like behaviour, delayed stress relaxation, and associated reduced lifecycles.