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ScotAsh materials cut cost and duration of road repairs

In-situ roads maintenance using hydraulic and pozzolanic binders from ScotAsh, can slash the cost of essential repairs and minimise traffic disruption, while offering a more sustainable alternative to conventional techniques.

With significant investment required to bring the nation’s roads up to standard, this must be welcome news for local authorities and the highways agencies.

ScotAsh, based at Longannet Power Station in Fife, manufactures hydraulic and pozzolanic binders from a mixture of fly ash and cement. The resulting pozzolanic material produces a greater volume of cementitious hydrates in the presence of lime than cement alone, providing a much more powerful binder.

ScotAsh binders been used with great success in various in-situ stabilisation projects, where the damaged road surface is excavated, milled with the binders and then re-laid to create a new surface.

The in-situ technique, using ScotAsh materials, was used in trials five years ago to restore the historic carriage drive in London’s Finsbury Park, where the badly degraded surface was repaired using in-situ stabilisation, saving more than a third on the tender price of a conventional repair.

More recently, ScotAsh binders have been used by companies such as Stabilised Pavements Ltd for in-situ road repairs in Dumfriesshire and Stirlingshire.

A recent example was the in-situ stabilisation of a one kilometre stretch of the A81 Aberfoyle to Glasgow road in Stirlingshire, which had been left badly damaged by frost and snow last winter.

Approximately 7,000m2 of road was renewed in five days, compared with the 2-3 weeks it would have taken to complete a contract using conventional repair techniques, helping to reduce inconvenience for motorists.

Gerry Howe, Managing Director of Stabilised Pavements said: “Recycling in-situ is more cost-effective and saves on natural resources – the road is our quarry, providing all the aggregate we need.

“The thermal effect created by the ScotAsh binders allows us to go for a 28-day curing strength, instead of seven days, which gives us a wider window of working, while any cracking problems are self-healing. Another advantage is that if we are working on a tar bound road, recycling with fly ash materials locks in any contaminants.”

In-situ stabilisation results in quality road repairs, with a durable finish, using up to 90% recycled materials – and there are other environmental benefits too.

Chris Bennett, ScotAsh’s Sales & Quality Manager explained: “This technique conserves raw materials and fuel, as no new materials  – apart from the binders – need to be transported to the site and it allows existing material, including high-grade stone that has already been paid for by the tax-payer to be re-used, rather than landfilled.”

He added: “The process also saves energy, as the materials are not heated. Transport impacts – including traffic congestion, vehicle emissions and road safety risks –  are significantly reduced as the “waste” material is treated on site rather than being removed to landfill and new materials being brought in. Stabilising just 1,000 cubic metres of existing material in-situ can save up to 400 lorry movements.”

Following completion of the A81 contract, a spokesman for Stirling Council said: “This innovative project helped us save around 20% on costs, one week’s work time and not having to transfer aggregate to landfill resulted in fantastic environmental benefits. It’s a win-win situation.”