Open graded (OG) mixes are known to provide good drainage and high skid resistant surfacings. These properties are particularly desirable at intersections and sharp curves (especially in wet weather condition), where braking, accelerating and turning actions frequently occur. However, OG mixes are not normally recommended at these high stress areas, due to concerns under severe traffic loading (slower traffic speed, turning of heavy vehicle, etc). Although rut resistance may be monitored by wheel tracking testers widely available, no simple laboratory test has been developed to measure the resistance against horizontal stress generated by traffic loading (i.e. skidding tyres). This paper looks into the development of a simple laboratory test to measure the resistance of OG surfacings against horizontal stress generated by skidding tyre. A wheel tracking tester was modified to have a skewed wheel (with a treaded pneumatic tyre). The test was performed on a series of OG specimens (with different binders) and other typical surfacings (dense grade and stone mastic asphalt). The results showed distinctively better performance for the OG mixes with PMB and multigrade binders, compared to those with conventional binders. (a) For the covering entry of this conference, please see ITRD abstract no. E217099.
Abstract