A substantial proportion of the secondary roads in the United Kingdom have thin bituminous surfacings and these roads are regularly maintained with surface dressings, as chip seals are known in the UK. More major roads are also often maintained using this treatment. Treatment is intended to provide both texture and skid resistance to the surface, to seal the road surface against ingress of water and to arrest disintegration and hence extend the life of the pavement and assist sustainable development. Surface dressings in the UK have been designed to Road Note 39 since 1972, during which time the method has developed with the sixth edition being published earlier this year. The method is based around the concept that the size of the aggregate should be greater for softer existing surfacing and heavier levels of traffic so as to maintain the required texture depth. The development of the design method has come about with the introduction of more complex types of surface dressing, the change in types of binder (greater use of polymer-modified bitumen and the end to using of tar, tar-bitumen blends and, most recently, cut-back bitumen) and the need to consider additional properties, in particular noise. (a) For the covering entry of this conference, please see ITRD abstract no. E217100.
Abstract