The sustainable option

Increasingly, the ability to repair and renew, rather than reconstruct, is being recognised as the way forward for real long-term sustainability. However, many local authorities have yet to grasp this concept when it comes to maintaining their highway networks, believes Howard Robinson, chief executive of the Road Surface Treatments Association

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.

Changing the approach
The fact that repair and renew is a more sustainable approach for road maintenance means that those local highway authorities that fail to properly realise the potential of surface treatments are failing to meet their own and the Department of Tranport’s sustainability objectives. These are summarised in the Agency’s ‘Sustainable Development: Vision and Action Plan 2009-10’ as being: “To provide a national network that allows safe, efficient movement of good and people, in a cost effective manner which minimises environmental and social harm and seeks enhancements wherever possible.”
Ongoing expensive and natural resource depleting programmes of structural reconstruction and replacement are not the best way to meet this objective. In addition, by offering solutions that are less energy intensive and generate minimum or no waste, road surface treatments help local authorities to meet their National Indicator 185 – CO2 Reduction for Local Authority Operations, and National Indicator 186 – Per Capita CO2 Emissions in the LA Area obligations. These were set up to measure the annual progress of local authorities in reducing the CO2 impact of their services provision.
For example, under NationaI Indicator 186, local authorities are required to support carbon emission reduction strategies for their local area. One significant area where CO2 reduction can be achieved is through the use of road surface treatments that can help to lower the embodied carbon in highways. Yet when it comes to meeting the carbon footprint reduction requirements of the National Indicator 186, many local authorities are ‘talking the talk but failing to walk the walk’. That was proven at last year’s Conference on Transportation Delivery at Loughborough University – when questioned over the implementation of carbon emission reducing strategies for local highways, Andrew Walford, service head for Environment and Regeneration at the Audit Commission, said: “I am aware that of all local authorities only six currently are in step with the requirements of NI 186.” He recommended that divisional and county surveyors should be reminded of their obligations to progress plans towards meeting the requirements of the indicator.
Local authorities need to be fully aware of NI 185 and NI 186 and of their need to reduce their carbon footprint. The correct use of surface treatments on their road network should form part of their carbon reduction strategy. However, only a few have developed and implemented real plans to reduce the carbon footprint of their road network. The majority are talking the talk, but failing to walk the walk.

Innovative treatments
There is a whole range of innovative surface treatments now available that can substantially prolong the service life of roads by restoring the skid resistance, 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 micro-asphalts have been developed to give retained macro-textures similar to thin asphalt surfacing. Widely used on the continent they have yet to be widely used in the UK. Surface treatments such as mechanical re-texturing 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. This is a further example 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 per cent. Velocity patching is a further example of product innovation that provides rapid pothole repairs with the minimum disruption to the road user.

Highly efficient
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, the Highways Agency estimates 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. The technique is currently being used on the M40, junctions 10-15.
Road recycling techniques, which use the existing road as a linear quarry thus minimising the need to use quarried aggregates, and the use of geo-textiles 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. Road surface treatments have considerable potential to not only significantly prolong the service life of roads but can achieve this sustainably thereby helping local authorities to meet their carbon footprint obligations.
In addition to sustainability, the issues of performance, cost and efficiency must also be addressed. Here there are a number of new products and approaches to watch out for. One such product is REphalt, which is available from Prismo Traffic Products. It is a pothole repair material that is applied cold, can be trafficked immediately and provides permanent repair that can be created in just one site visit. The product has recently been approved for use on major roads by HAPAS – the Highways Authorities Product Approval Scheme.
Another new product is Vegecol, a new vegetable-based binder offers a natural alternative to bitumen or petroleum resin based binders. The binder is available from highway maintenance and materials specialist Colas. It has been successfully used is surface dressing applications and as the binder in surface and base course asphalts in continental Europe for several years. The binder is now gaining recognition in the UK following its use in Portsmouth in 2007 and through further pilot projects carried out last year and this. Vegecol is transparent and so can produce naturally aesthetic or coloured asphalts with the addition of pigment or decorative aggregates. The vegetable-based binder can help lower the temperature at which asphalt material is mixed by as much as 40 degrees. This results in reduced fuel consumption and fume emissions from the production plant.
Meanwhile, the question asked by many following this year’s sever winter is ‘how can we stop potholes from forming. The answer could be Rhinophalt, a preservative treatment provided by ASI. Highway authorities have reported that following this year’s winter those roads threatened with Rhinophalt have performed well with no remedial winter maintenance required or sudden deterioration occurring.

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