New industry guidance from the Road Surface Treatments Association (RSTA) and council directors' body ADEPT provides best practice and technical information on asphalt surface course preservation treatments.
The guidance note outlines the process of asphalt preservation and highlights the responsibilities of client, contractor and installer concerning planning and co-ordination, health and safety, environment and work execution.
Reference is also made to the relevant regulations, standards and training qualifications.
'Products used for Asphalt Preservation must be manufactured under BS EN ISO 9001. Additionally, Asphalt Preservation Treatments can be independently certificated under the Highway Authorities Product Approval Scheme (HAPAS) or equivalent product acceptance scheme certification,' the guidance states.
Welcoming the new guidance, Rory O’Connor, RSTA interim chief executive, said: 'The new guidance note provides information on the right way to apply asphalt preservation treatments and gives practical advice to both client and contractor. Its use will ensure best industry practice that will result in the successful application of asphalt preservatives.'
Asphalt preservatives involves the spray application of a sealant treatment onto bituminous-bound road surfaces that consequently restricts water ingress and inhibits binder oxidation.
By providing a protective seal, it can significantly extend the performance life of an asphalt road surface, but it will only work on bituminous bound surfaces.
There are two types of preservation treatments, penetrative and non-penetrative:
- These are solvent-based and as such on application facilitate some penetration of the binder coating.
- They comprise a blend of bitumen and/or, hydrocarbon resins, diluents, plasticisers and may be fortified with natural-based bitumen.
- These are bituminous emulsions.
- They comprise of proprietary blends of bitumen, polymers and other additives designed to seal and protect the road surface.
The guidance advises: 'It is important that current skid resistance data is available when considering the application of a preservation treatment to a high speed road.
'Preservatives should only be considered where readings are adequately above the relevant investigatory level/s, as there is usually a temporary decrease in skid resistance post-application. However, the skid resistance levels will return to their original values, the rate of this is proportional to the site’s traffic levels.
'The installer will determine if additional measures are needed to maintain adequate skid resistance.'