Types of road surface treatment

In Cambridgeshire, we use different types of road surface treatments:

• Micro Asphalt / Gripfibre
• Surface Dressing
• Footway Slurry Seal
• Crack Sealing
• Retread
• Carriageway Textureblasting

Micro Asphalt and Gripfibre

Micro-Asphalt is a cost-effective surface treatment best used on roads showing early stages of wear and tear. The material laid is a cold liquid emulsion containing stones of varying sizes. We lay it over the top of the existing road surface to seal and protect it. This treatment:

• Prevents further deterioration of the road
• Extends its life
• Improves skid resistance

We can lay Micro-Asphalt in temperatures as low as five degrees. This allows us to carry out work between March and November. Micro Asphalt is a weather dependent treatment, meaning we can’t lay it if the weather is wet or too hot or too cold.

We sometimes use a more enhanced variant of Micro-Asphalt called Grip Fibre. We can use this variant on busy roads as it is stronger, but the season for laying this runs from May to August.

Before the main works, we prepare the road to ensure it’s in a suitable condition for us to lay the Micro-Asphalt. Preparations may include removing overhanging vegetation, weed killing, patching and sweeping.

Following completion, we adjust ironworks (e.g. drain covers) if required. The new road surface can shed some loose stones over the first few weeks after treatment. This is typical and we sweep the road as required. The new surface may appear messy after laying but it settles down after a few weeks and resembles a normal road.

Surface Dressing

Surface Dressing is a cost-effective way of maintaining a road. It involves spraying the existing road surface with a coating of liquid bitumen. We then roll stone chippings into the bitumen to form a protective, water-resistant layer. Once the bitumen has set, we sweep the road to remove loose chippings and return to do this until the road settles down. We replace road markings afterwards.

Although Surface Dressing doesn’t repair roads with structural issues, we can use it as a preventative method and treat roads with minor defects. This treatment:

• Prevents potholes
• Restores skid resistance to make the road less slippery
• Seals the road to prevent water seepage
• Gives the road added texture
• Gives conformity to a scarred surface
• Extends the life of a road by up to 10 years

The laying season for Surface Dressing runs from April to September. This type of treatment is weather dependent, meaning we can’t carry out work if the weather is wet or too hot or too cold.

Footway Slurry Seal

Footway Slurry Seal is a low-cost, preventative maintenance process, designed to seal in the surface of a structurally sound footway and extend its life. It fills in minor depressions and voids and provides a more even surface, improving the quality of slip resistance.

Slurry is a mixture of bitumen emulsion, aggregate and water. We spread it over the existing footway and brush it to give a textured finish. Before laying, we may have to prepare the existing surface by cleaning, weed spraying, minimal patching and raising ironwork.

Although a quick process, the surface remains wet for several hours following treatment so we close the footway until it dries.

As with all thin coat surfacing, this process is weather and temperature dependent. We can’t lay the slurry if the weather is wet or too hot or too cold.

This treatment type isn’t suitable for use on a footway that isn’t in a structurally acceptable condition and doesn’t add strength.

Crack Sealing

Crack Sealing works are an essential part of maintaining the structural strength of a road surface. If untreated, cracks may deteriorate and develop into potholes.

We seal cracks in the road to prevent the ingress of water which can cause severe damage to the layers of road construction. In the winter, ice and freezing conditions can cause significant damage to a road by widening cracks. As the surface degrades, the crack turns into a pothole.

Crack Sealing is an important highway maintenance tool. Like carriageway patching, we can use it to help prepare a road for further surface treatment such as Surface Dressing or Micro Asphalt.

We undertake Crack Sealing repairs by milling out a shallow rebate in the road surface, sweeping up the chippings and cleaning the surface ready for the repair. We then fill the rebate, sealing all the edges with a hot rubberised bitumen mix that contains aggregate, recycled rubber and chopped fibres to reinforce the material. 

While it's still hot, the material receives a coating of fine granite aggregate chippings which provides a non-slip surface. When the repair has cooled down (which can take between 30 minutes and one hour), it is again swept clean, and can then be driven over as normal.

It is usual for crack repairs to have a small lip along the edge where it seals the road surface. Once completed, this embeds and flattens down as cars drive across the surface.

While the material cools down, it is important not to drive over the repairs as the molten bitumen compound sticks to tyres. For this reason, we may close the road for a short time until the area is suitable for vehicles to drive over.

Retread

Retread is a process where an existing road surface is planed up, re-graded and re-profiled on site. It is then compacted down and receives either a surface treatment or a tarmac overlay. It is suitable for roads that have deteriorated but don’t have particularly heavy traffic flow.

Carriageway Textureblasting

Retexturing of the carriageway is a cost effective way of restoring a road surface. It provides a safe, durable road with the important characteristics of skid resistance and texture to ensure that vehicles have sufficient grip when using the road, especially in wet conditions.

The mobile plant involved in the process is a specially constructed piece of machinery. It uses high pressure water at around 1000bar to remove deposits of bitumen from the road surface. This re-exposes the aggregate within the road. The waste material is vacuumed up at the same time and stored with the vehicle until the end of the work. It is then transferred to a licensed waste carrier.

Schedule of road surface treatment works

Visit our road improvements page to see which roads we have scheduled for works.

Report an issue with a road surface

To report an issue with a road, please visit our report a highways fault page.