The UK road network is under increasing pressure from ever growing traffic weight and volumes, shrinking highway budgets and, increasingly, from national and local government sustainability agendas. All this calls for a re-examination of road maintenance procedures and for an emphasis on solutions that enable roads to last longer without the need for structural reconstruction or dig out and replace.
The fact that prevent and repair is a more sustainable approach for road maintenance means that those local highway authorities who fail to properly realise the potential of surface treatments are failing to meet their own and the National Highways sustainability objectives. These are summarised in National Highways Net Zero highways 2030 / 2040 / 2050 plan. All local authorities have now declared a climate emergency and for those managing local highway networks, their highway operations are their largest generator of carbon. Drawing large quantities of natural raw materials for conventional asphalt replacement is no longer viable. The RSTA Carbon Emissions for Road Surface and Other Maintenance Treatments for Asset Management Purposes Guidance details the embodied carbon emissions for surface treatments, In-situ recycling and conventional asphalts, and enables local and national roads authorities to demonstrate their carbon savings of up to 75% that can be made by planning and implementing whole carbon lifecycle planning in their highway asset management Document Gallery – RSTA (rsta-uk.org)
There is a whole range of innovative surface treatments now available that can substantially prolong the service life of roads by restoring skid resistance, preventing and filling pot holes and sealing the pavement. Early intervention with these treatments can significantly reduce the frequency of structural reconstruction. Unfortunately, surface treatments are often wrongly perceived as being limited to ‘tar, spray and chip’. The reality is very different.
For example, durable microsurfacings have been developed to give retained macrotextures similar to thin asphalt surfacing. Widely used on the continent and throughout the UK by many local authorities. Surface treatments such as mechanical retexturing that can restore skidding resistance and extend the life of the surface course have been available in the UK for sometime. However, the market has not grown as might be expected. Modern computer controlled surface dressing sprayers can apply bitumen emulsion at rates that vary transversely across the lane width. Encapsulation systems can also be used to ‘lock down’ the chippings and give the appearance of a conventionally resurfaced road. These are further examples of the extent to which the surface dressing industry has embraced innovation resulting in improvements in quality over recent years.
Infrared road repair is another useful treatment. This provides a right, first time reinstatement that reduces the need for new materials by up to 90%. Spray injection patching is a further example of product innovation which provides rapid pothole repairs and surface dressing pre-patching with the minimum disruption to the road user.
Maximising the efficient use of resources is a cornerstone requirement of sustainability and it is one that surface treatments are fully able to meet. For example, National Highways estimate that between 20,000 to 60,000 tonnes of aggregates are used to construct a mile of motorway. Ensuring the long life of motorways is therefore a sustainable must do. The use of asphalt preservation techniques such as sprayed stabilising solutions can significantly extend the serviceable life of a road surface.
Road recycling techniques, which use the existing road as a linear quarry thus minimising the need to use quarried aggregates, and the use of geosynthetics and steel meshes to reduce reflective cracking in asphalt pavements are other examples of surface treatments that should have a key part to play in helping to meet sustainability agendas and highway budgets. Last but not least, high friction surfacing using a combination of calcined bauxite aggregates and tough binders can provide unrivalled skidding resistance when applied to road surfaces to help reduce traffic accident fatalities – a measure of sustainability that is often overlooked.
What all these treatments have in common is their strong sustainability credentials. They provide a real sustainable alternative to structural maintenance and reconstruction by offering solutions that are less energy intensive and generate minimum or no waste, thus helping local authorities to meet their NI 185 and NI 186 carbon reduction obligations. In addition, they provide considerable cost economies that enable both national and local highway authorities to get best value for their pressurised budgets. Sustainable and cost-effective, road surface treatments offer a win-win solution.