Having well maintained road surfaces with adequate skidding resistance helps to minimise traffic accidents and delays the need for structural maintenance thereby helping to reduce high maintenance costs. There is a considerable range of surface treatments available the use of which is determined by a number of variables such as road type, location and volume and speed of traffic.
Surface Dressing is a long established proven highway maintenance technique. In simple terms it involves the even spray application of an emulsion bituminous binder through a purpose built spray tanker onto the existing road surface followed immediately by the even application of aggregate chippings to ‘dress’ the binder.
High Friction Surfacing
High Friction Surfacing has a long history of proven use in saving lives by imparting the highest level of skid resistance onto a road surface. High Friction Surfacing is available as hot or cold applied systems. The cold applied technique involves the even application of a tough polymeric liquid binder onto the road surface followed by the application of calcined bauxite aggregate. The hot applied systems involve the application of a hot pre-mixed material consisting of binder and calcined bauxite.
What is Slurry-Micro Surfacing?
These materials are cold-applied, thin bituminous surface courses incorporating bitumen emulsion and fine graded aggregate with fillers.
Retexturing is described in the Design Manual for Roads and Bridges ( DMRB ) as the mechanical reworking of an existing surface to improve its frictional characteristics and hence its skid resistance.
For information on the various types of aggregates, visit the Mineral Products Association website:www.mineralproducts.org
Geosynthetics and steel meshes for use in pavements and asphalt overlay
Geosynthetics and steel meshes are increasingly being used as a means of extending the life of existing or old road surfaces across Europe. The system can be used in conjunction with a surface dressing technique for short to medium term benefits, in the reconstruction of existing roads following the milling / planning process to remove the top surface or in new construction where the benefits can be designed in to the project.
Spray Injection Patching
A rapid patching technique suitable for use on rural and urban roads using cold emulsion asphalt which is placed into the void depression in the road surface under high pressure. The void is first blasted with compressed air to clean the surface and remove any debris, then the surface of the void is sprayed and coated with bitumen emulsion. Finally the asphalt is blasted into the void, self compacting from the bottom up so requiring no additional compaction.
Thermal Road Repairs
The principal of this technique is to re-heat the damaged area on the surface course using targeted infra-red then re-work the warm mobile asphalt material with a small addition of emulsion binder and aggregate as necessary, followed by compaction to make good the patch.
Preservatives work by applying a mineral based solution (e.g. Gilsonite) onto the existing surface course. This penetrates below the surface to a depth of a few millimetres dependent on the type of asphalt surfacing creating a Gilsonite rich membrane which binds together aggregate and surface fines. This membrane seals the pavement against water and salt ingress and seals in essential oils and resins.
Road Recycling and Stabilisation
The principal of road recycling is to use the existing road effectively as a linear quarry by recycling the existing worn out road back into a structurally sound pavement structure. Unlike the other surface treatments this technique involves deep layer recycling so in effect the full road depth can be treated and recycled. Or alternatively the process can be used to stabilise a foundation layer (soil stabilisation) as part of new works prior to overlaying with sub-base and bound layers.
Road Surface Condition Monitoring
The RSTA also represents member companies who provide innovative testing services to measure the skidding resistance of road surfaces. Highway authorities have a responsibility to the public to ensure that appropriate skid resistance is provided across the whole network, both for safety reasons in respect of skidding and to provide a defence in case of litigation (Code of Practice for Maintenance Management, published by The Institution of Highways and Transportation).
Semi-rigid Industrial Surfacings
These products and systems are extremely hard wearing and suitable for a range of industrial applications. They usually involve the installation of a porous asphalt surfacing which is then grouted with a tough liquid polymer which penetrates into the asphalt.
Asphalt Grouted Macadam
These materials involve the laying of a semi-porous macadam which is grouted with a bituminous based liquid to provide improved ride quality, an impervious layer to protect the underlying substrate and a reinforced surface with added flexibility. Their designed use is on rural and residential carriageways with particular benefits when resurfacing concrete roads.