Table of Contents

3.4.3 Surface Enrichment and Rejuvenation Treatments

Surface enrichment of a sprayed seal surface involves the spraying of a light application of a low viscosity grade of bituminous material (cutback or bitumen emulsion) or foamed bitumen onto the surface so that it runs into the voids of the existing surfacing. This treatment increases the amount of binder in the layer, but care must be taken to ensure that adequate surface texture remains. This treatment extends the life of the surfacing by ensuring the retention of the existing cover aggregate. Surface enrichment is generally applicable to low traffic sites such as shoulders and rest areas, and may also assist in waterproofing the surface.

A rejuvenating treatment is the application of a proprietary rejuvenating agent, usually in the form of an emulsion. Rejuvenation is used to replace the lost oils and resins in oxidised bitumen. Rejuvenation materials have a lower viscosity than the bitumen materials used in surface enrichment. They are particularly applicable to asphalt pavements for reducing permeability and delaying the onset of ravelling through ageing and oxidation of bitumen binders.

Enrichment and rejuvenation treatments are normally only used on roads in essentially good condition apart from aged binder where there is a risk of aggregate loss. They are generally only practical where traffic volumes are low and traffic can be diverted onto another lane or road, or the road shoulders. Traffic should not be allowed onto the treated surface until the binder has cured sufficiently to avoid pick‑up. In some cases, a light coating of sand or grit can be used to reduce the time before trafficking.

Surface enrichment and rejuvenation can result in reduced skid resistance through a residue of surface binder. Traffic speed restrictions should remain in place until this residue has worn off and the skid resistance levels rise to acceptable levels.