This report surveys developments for surface-dressing techniques and specifications since 1970. Technical improvements in united kingdom surface-dressing specifications are discussed, particular reference being made to their development for use on the most heavily trafficked roads, both bituminous and concrete. The definition of traffic (particularly of the volume of commercial vehicles) and of road surface hardness are considered as critical factors in specification preparation. Also dealt with are the associated engineering developments in machinery for applying binder and for spreading chippings. Another important aspect is the provision of adequate traffic management during and after surface-dressing operations; suitable regimes for use on a range of road layouts are introduced. Recent research and full-scale road experiments carried out at TRRL are described. Mention is made of the development of improved binders with the high cohesive strength required to cope with additional shear stresses imposed on surface dressings by braking and turning traffic and the preparation of specifications for the use of high-bitumen-content cationic road emulsions. It is concluded that roads scheduled for surface dressing may in future require treatment in two stages. Conventional materials would be used on unstressed lengths, whereas difficult areas would require the use of specially modified binders. (Author/publisher)
Abstract