Methods of Repair

Surface Dressing

Surface dressing is the application of hot bitumen and chippings to the road surface. It is one of the most cost effective methods of highways maintenance available and is very widely used, but is not usually suitable for high stress sites e.g. roundabouts.

Surface dressing seals the road to prevent the ingress of water and the bitumen forms a protective barrier against rain and frost to protect the road foundations, significantly extending the life of the road. Surface dressing also restores skid resistance leading to increased safety as well as enhancing the appearance of the road.

Once the bitumen and chippings have been laid, a heavy roller provides an initial degree of embedment but the real work of consolidation is provided by the traffic. Shortly after application and rolling, the road is swept and markings applied, usually within 2 to 4 working days.

Surface dressing, has a limited life of between seven to fifteen years depending on traffic and environmental factors.

If the foundations of a road have collapsed, surface dressing cannot provide additional strength. In such circumstances it will be necessary to Resurface or Reconstruct.

Micro Asphalt Surfacing

Slurry seal is a relatively cheap material consisting of a bitumen emulsion and aggregate slurry, which is laid cold by a paving machine following the existing shape of the road or footway surface. It seals the surface and improves skid resistance and has very good stress absorbing characteristics. It will normally last between 5 and 10 years.

Micro-asphalt Surfacing is a multi layer version of Slurry Seal and can restore a desirable profile, improving ride quality. It is typically undertaken on busy urban thoroughfares, housing estates, roundabouts and motorway hard shoulders. The finished surface has low noise characteristics, and good riding qualities. It is an efficient process that allows us to reduce time spent on site and minimise disruption.

High Friction Surfacing

When the road surface is wet, skidding resistance is lowered and accident potential increases. While traffic levels have risen over recent decades, the use of high friction surfacing at crossings, road junctions and other potential danger points has contributed to an overall reduction in the number of pedestrian accidents.

The term high friction surfacing covers a range of material types with differing costs, effectiveness and durability.

Conventional Surfacing

Resurfacing is designed to restore the surface profile of a road, usually for rideability and drainage purposes and to provide improved texture and skid resistance.  The resurfacing usually takes the form of Inlay or Overlay.

Inlay is where the old surface is planed off and replaced by a new one.  This can also involve the base layers to give additional strength.  This is normally done where the existing surface has failed badly and could not support a new surface or where restraints such as kerb levels, accesses etc prevent the road level being raised. Inlay is most common in urban situations.

Overlay consists of adding material on top of the existing road to improve the profile and add strength and is more common in rural situations. As well as overlaying the surface localised reconstruction may be required before the road is overlaid. The most common material currently used is stone mastic asphalt (SMA) along with bitumen macadam and hot rolled asphalt. The laid thickness is normally between 25-50 mm.

Re-tread (Carriage way reconstruction)

Where the carriageway pavement or footway is beyond repair then conventional or retread reconstruction is necessary.

'Retread' is an in-situ recycling process and is more 'environmentally friendly' than some other treatments. It involves treating the top 75mm of the existing road, milling down the existing surface and adding bitumen and aggregate (if necessary). The surface material is then regraded and rolled to form a re-vitalised pavement. The surface is finally sealed with a surface treatment as part of the process.

Pavement failure may be attributed to any one or a combination of the following:-

• Sub-grade softening due to poor drainage.
• Sub-grade softening due to ingress of moisture through cracked and pervious pavement layers as a result of progressive oxidisation.
• Sub-grade failure due to insufficient pavement thickness.
• Frost Heave