Masterlayer in Glamorgan
Masterlayer used to resurface Glamorgan roads
Efficient resurfacing on the road to savings
When the surface of a main commuter route into Cardiff began to suffer from acute deformation, Vale of Glamorgan Council required a durable and faster alternative to hot-rolled asphalt to ensure minimum disruption for local road users.
The B4267 Sully Moors Road near Barry is a busy road, used by commuters, parents taking children to school and heavy goods vehicles. The sizeable strain on the road had resulted in subsidence and severe rutting in the road surface, made worse by the large number of utilities trenches running through it.
Ken Evans, senior highway maintenance officer at Vale of Glamorgan Council said: “The initial plan to resurface the one kilometre stretch of road with traditional hot-rolled asphalt would have required full closure of Sully Moors Road. This would have caused significant disruption for residents and businesses resulting in an eight mile diversion for workers requiring access to a nearby chemical plant.”
Surfacing issues on the road were made worse by its tendency to flood as it runs through wet moorlands. Evans explains: “Water running under the surface to the sub-base of the road was washing away fine pieces of aggregate, compromising the integrity of the existing hot-rolled asphalt, where it had begun to crumble under heavy use and crack when frozen.”
Vale of Glamorgan Council, which has a £1 million annual resurfacing contract with Tarmac National Contracting, worked in partnership with Tarmac to find a durable, quick and efficient resurfacing solution. Tarmac examined the issues surrounding the B4267 and the needs of local residents, and recommended Tarmac Masterlayer as a high-quality alternative to hot-rolled asphalt: “ a solution that would allow the road to remain fully open at peak times.
Masterlayer was also specified because it could address the problem of water erosion as its composition is much harder and more durable than hot-rolled asphalt, increasing the structural stability of the road.
Technical detail
Designed by Tarmac’s technical team, Masterlayer is an innovative binder and surfacing material. It uses a high performance, heavy duty, Polymer Modified Bitumen (PMB) supplied by Nynas Bitumen that has been used extensively on very heavily trafficked sites with high loads. It is formulated using a combination of specialist additive technology together with high quality rheologically-enhanced bitumen that is designed to increase the asphalt's elastic and cohesive performance. The binder allows an asphalt mixture to be designed and produced with an increased binder content, which helps to ensure the long-term durability of the road and reduces the amount of wheel rutting caused by large volumes of heavy traffic.
In its development, Masterlayer was meticulously tested over a number of months in Tarmac’s central laboratory. As one of the only UK suppliers to have a French wheel tracker, Tarmac also undertook rigorous ‘real-life’ trials on deformation resistance of the pavement’s lower layers as the wheel tracker was able to simulate the high loadings that the roads experienced.
“Because Masterlayer has better workability at lower temperatures than traditional hot-rolled asphalt, there is the potential to allow vehicles onto the asphalt surface at an earlier stage,” said Mike McAndrew, general manager for Tarmac National Contracting in Wales. “This helped minimise disruption and meant that the road could reopen to traffic much sooner than would have been possible if a conventional asphalt had been used.”
Design and construction
The new 45mm thick Masterlayer was laid on a planed surface using a 10mm hardwearing polymer modified surface course to provide a closed finish. The design incorporated variations in the depth of the construction of the road, particularly to address minor reflective cracking outside the entrance to the chemical plant where the road had a further 100mm of inlay applied with 0/20mm heavy duty binder course on top.
More than 700 tonnes of material were supplied by Tarmac’s Cornelly quarry near Bridgend as part of the contract.
Alleviating traffic congestion while the work was carried out was a major consideration for all parties, particularly as possession time between 9.30am and 3.30pm included the school run. Using hot-rolled asphalt would have required full road closure; however the use of Masterlayer allowed a single flow of traffic during possession time using stop and go traffic management and, at peak times, the heavy duty binders within the new surface meant that the road could be reopened to two lanes.
As well as being trafficable within an hour of laying, the new Masterlayer surface was laid in one application, reducing the project construction time by half. This saving, coupled with the need for less labour and plant to carry out the resurfacing, ensured that costs were cut by around 30 per cent.
“Because Masterlayer solutions require less construction time and materials compared to full depth construction and are designed to last much longer than simple patch-up products - Masterlayer is not only more cost effective than traditional hot-rolled asphalt, but more sustainable too, so we were able to stretch our client’s budgets further, whilst reducing our carbon footprint,” concludes McAndrew.
See more on: Masterlayer
30 April 2010
Masterlayer benefits
- Enhanced resistance to reflective cracking and permanent deformation.
- Cost-effective - less construction time and materials stretches your budget.
- Can avoid the need for full depth reconstruction.
- Faster construction time and less disruption to the road user.
- A more sustainable option through thinner pavement design.
- Utilises stronger and more flexible materials which enhance structural benefit.
- Low voids reducing potential for water damage and improved durability.
- An alternative to the use of geo-textiles.
