Surface treatments: surface dressing, slurry surfacing and slurry-surfaced surface dressing

Laying of a single surface dressing

Laying of a red slurry surfacing

Surface treatments are maintenance techniques mainly intended to improve the imperviousness of a road surface to water or to restore its skid resistance. Furthermore, these techniques are also suitable, after repairs, for giving the road an even aesthetic aspect or allowing better segregation of the various types of road user on the carriageway by using coloured sections and zones. Three different techniques are used for surface treatment:

  • surface dressing;
  • slurry surfacing;
  • slurry-surfaced surface dressing.

A surface dressing is a surface treatment which consists in fixing onto the road surface to be treated a “shoulder-to-shoulder” mosaic of chippings spread in one or two layers (to the thickness of a single particle) on a previously spayed coat of (bituminous or resinous) binder. Three main types of surface dressing are distinguished: single, double, and single with double chipping (or “racked-in”). Coloured chippings are optional for each of the three types. More information can be found in BRRC’s code of good practice R71/01 (Code de bonne pratique pour les enduits superficiels).

Slurry surfacings are used as surface treatments as well. A slurry surfacing consts of a mixture of mineral aggregates, bitumen emulsion and optional additives, which is mixed and poured in place. It can be laid in one or two layers, which may be coloured or not.

Surface dressings and slurry surfacings both have their advantages and disadvantages. The disadvantages of the two techniques can be cancelled out for the greater part by opting for a combination of both, namely a slurry-sealed surface dressing.