Work underwayI refer to my blog dated 18 Feb 2018 regarding the closure of the B1202 between Nocton Park Rd and Nocton Fen Lane.
|Potterhanworth Rd & Nocton Park Rd junction|
Road surfacesMost road surfaces are made of asphalt – a mix of stones bound together with bitumen and still colloquially called ‘tarmac’ (although tar is no longer used as a binder).
Asphalt is a flexible material able to flex and stretch a little when it is fairly new but the bitumen binder becomes brittle as it gets older. When this happens – typically between ten and twenty years into its life – cracks can open in the surface of the material.
Water can get into these cracks and freeze, widening the crack. In poor weather this ‘freeze-thaw’ effect can lead to a quick deterioration in the asphalt surface and the rapid formation of potholes. This is why potholes are so much more common in cold, wet weather.
If the deterioration goes too far, the surface may lose integrity and water can get through into the lower layers of the road, damaging them too. For this reason, keeping the surface sealed is key to getting the most life out of a road.
This type of surface failure is the most common cause of problems on most local authority roads in the country. The good news is that, caught early enough, the surface can often be resealed cheaply and effectively using a surface treatment to extend its life by ten or more years for a fairly modest cost.
Surface TreatmentsSurface treatments include surface dressing and thin surfacing such as micro asphalts. These all involve laying a thin layer over the top of the existing road to seal the surface and restore grip, extending the life of the road. They will also rectify surface defects like cracks and potholes, either as part of the treatment process or through pre-patching works done to the more significant defects in advance of the surface treatment.
Resurfacing usually involves removing and replacing the existing road surface (although it is sometimes possible to lay the new surface on top of the old). Resurfacing differs from a surface treatment by using a thicker layer of material; usually at least 30mm thick and sometimes 100mm or more if several layers of the road are replaced. Resurfacing restores the road surface to a new condition, removing surface problems and most unevenness.
RebuildingRebuilding works like recycling or reconstruction involve digging down to repair or replace some or all of the foundation layers of the road and then putting a new surface back on top. Limited areas of reconstruction are sometimes used to solve localised problems as part of a resurfacing scheme.
|Resurfacing Potterhanworth Rd|
|Rebuilding edge of carriageway|
|Potterhanworth Rd & Nocton Fen Lane junction|
Source: Extracts taken from 'An Introduction to Highway Maintenance' [https://www.hertfordshire.gov.uk]