We patch roads and most pavements using asphalt or other materials.
Patching work can cover both the surface layer of the road and the layers below the surface, depending on what is needed to give the road strength and stability.
Where a road is scheduled for surface dressing work, we pre-patch in advance to give a smooth and structurally sound surface for the surface dressing treatment.
We may pre-patch years before before the main work, because patching is often enough to solve immediate issues. We sometimes pre-patch the same area more than once.
For pavements on older housing estates, we sometimes use micro-asphalt patching. This is a cost- effective and successful treatment for pavements originally laid with thin surfaces that were too thin and have worn away. Newer housing estates don't normally suffer this problem because the standards developers must meet have been improved.
We can do patching work when weather conditions are suitable. The length of time it takes to do patching work depends on the depth we need to work down to and the quantity of material we need to replace.
Surface dressing adds a new layer on top of an existing road surface. It is a well-established and cost-effective preventative maintenance treatment.
We use surface dressing where a road is still structurally sound but the surface is causing issues for road users. The treatment both restores the road surface and adds a waterproof layer that protects the road from water and frost damage.
Restoring the surface increases skid resistance and improves the appearance of the road. Protecting the road from damage minimises the need for maintenance visits and disruption and keeps roads stronger for longer, reducing the need for expensive resurfacing work (resurfacing can cost up to 10 times as much as surface dressing).
When we programme a road for surface dressing, we patch particular problem areas first to give a suitable base on which to lay the new surface. Patching can take place several years before the surface dressing work.
We use both conventional and micro-asphalt surface dressing, depending on the circumstances.
Conventional surface dressing
For conventional surface dressing, we spray the road surface with bitumen and press in new stone chippings with a roller. On major roads, we apply two layers of both bitumen and chippings.
Micro-asphalt surface dressing
Micro-asphalt is a mix of bitumen binder and stones suspended in water with cement or hydrated lime. You might also come across the term ‘grip fibre’ - micro-asphalt with fibres added for extra stretch and strength.
Micro-asphalt goes on in 2 layers, each about 5mm. The first layer helps to fill cracks and smooth out dips, and the second gives the surface texture. The mix is blended on site and pumped onto the road.
Because the material is viscous, it does sometimes flow so that it’s a bit thicker against the kerbs than in the middle of the road.
The new surface is very black and can look messy, but it will gradually settle down and look normal again.
Surface dressing work takes place in the summer, because both types of surface dressing need warm dry weather (though micro-asphalt can tolerate cooler weather than conventional surface dressing). If the weather is not suitable, we might have to change planned dates or stop work and come back later.
Surface dressing normally takes 1 to 2 days. Micro asphalt can be quicker because it is laid cold and strengthens quickly. This means it can be ready for traffic within a few hours, though it continues to cure (harden) for some time after.
When more than just the very top layer of a road surface is in poor condition, the road will need resurfacing to make it structurally sound again.
On most roads, resurfacing involves removing the layers that are in poor condition and replacing them. This is called an inlay. On country roads where there are no kerbs or properties, we may be able to simply add a new surface on top of what’s there – an overlay.
Where we need to remove an existing surface, we bring in a planing machine to chew up the old surface using a rotating drum covered in teeth.
To lay a new surface, we first clean the road and spray it with bitumen to help the new surface stick. We then use a paving machine to lay a controlled thickness of hot asphalt onto the road.
As part of the work, we sometimes need to dig or plane deeper to fix structural problems. These problems are typically caused by blocked gulleys or by trench digging and reinstatement.
We can do full road resurfacing at any time of year. The length of time it takes to do resurfacing work depends on the depth we need to work down to and the quantity of material we need to replace.