Water is damaging to roads, particularly when it finds its way into the soil under the carriageway or footway. This is because it softens the soil, and this allows the road to flex. The surfacing materials can only flex so far before cracking, and when they do so, more water gets in and makes the problem worse. You will see crazing on the surface and often potholes where this has happened. It is therefore very important that road surfaces remain waterproof.
The skidding resistance of a road surface is important for obvious reasons, and this depends on the type of stone used in the upper layer of the road, and the roughness of the road – particularly when the surface is wet.
Surface dressing is a well established process which is used to sort out both of these problems. By spraying the road surface with bitumen, then pressing new stone chippings into the bitumen binder, the road surface is sealed against the ingress of water, and the surface texture is improved by the rougher surface and new stone.
Surface dressing is unfortunately not popular with road users, mainly because of the loose chippings which are an inevitable part of this process. However the work is carried out at considerable speed, which minimises the level of inconvenience on any given section of road when compared with other processes. The comparatively low cost of this process means that we can treat a much larger proportion of the road network each year.
The process is weather dependant:
The new chippings will not embed into the road properly if the road is too cold, and the binder will not hold the chippings down if it is too hot.The process will not work if the road is wet, or if there is heavy rain shortly after the work is carried out.
Consequently, we must be constantly aware of the weather forecast, and stop work if there is likely to be heavy rain in the next 24 hours.