Write a brief note on surface dressing in road construction

Surface dressing in road construction

It is provided over a prepared base course or existing pavement to serve as a thin wearing coat. Surface dressing work consists of the application of a suitable grade of bitumen or emulsion by spraying over a prepared base course or existing pavement surface followed by spreading a specified size of hard aggregates at the recommended rate and rolling.

The surface dressing doesn’t add to the structural stability or strength of the pavement nor will it improve the existing riding quality of the pavement surface. The BSD is a cost-effective surface treatment to provide a dust-free and impermeable pavement surface; thus, the ingress of rainwater into the pavement layers including the subgrade is minimized and consequently, the adverse effects of water in the pavement layer are reduced. The surface dressing also arrests the disintegration of the pavement surface and provides a non-skidding surface.

There are only two types of surface dressing suggested by IRC.

1. Single-coat surface dressing
2. Two-coat surface dressing

Two coat surface dressing is formed by spraying the first layer of binder, spreading a layer of cover aggregates, and rolling, which forms the first coat.

Over the first compacted layer, the second layer of binder is sprayed, and the second layer of cover aggregates is spread and rolled. The aggregate size of the second one is lesser than the first one. Single coat one suits for low volume traffic roads.