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National Highways and Redbridge Council put carbon negative aggregate to the test


This month [July] there has been news of two new trials of a carbon-negative aggregate for National Highways and Redbridge Council.


Low Carbon Materials’ (LCM’s) aggregate ACLA, is created by sequestering carbon into waste material. When used as part of an asphalt mix, ACLA reduces the embodied carbon of the road materials up to the point it is laid in the road. Real-life trials will help to assess its performance over the lifetime of a road, which is important from both an operational and carbon cost perspective.


Skanska laid a test strip with a binder course containing the carbon negative aggregate, supplied by Tarmac, on a strip of the northbound carriageway of the M11 in Essex, as part of resurfacing and maintenance works between junctions 7 and 8 for National Highways. Its performance will be observed alongside a control strip containing 100% conventional aggregate.


Meanwhile, Redbridge Council deployed the aggregate in the binder course of resurfacing works at Lodge Hill, Ilford. Tarmac supplied the mix for the trial, while Kensons Highways laid it. According to the council, the use of ACLA lowered the carbon footprint of the road – presumably up to the point that the asphalt is laid – by 68%.


LCM has developed the carbon negative aggregate in partnership with Skanska and Tarmac, with funding through National Highways’ Accelerating Low Carbon Innovation competition, in collaboration with Connected Places Catapult, launched last year. The competition sees four firms receive up to £80,000 to progress their ideas. The M11 trial was the first time that ACLA has been laid on a National Highways operated road.


In March this year, Durham County Council became the first highway authority to trial ACLA on Elvet Hill in Durham, working with its roads resurfacing contractor Rainton Construction, part of the MGL Group. LCM came out of Durham University and is based locally in Seaham, County Durham.


Cutting the embodied carbon of materials used in road construction and resurfacing is vital, but cutting carbon spent in operation and maintenance is equally necessary. Whole life carbon incorporates the carbon spent on maintenance, repair and resurfacing – as well as the initial embodied carbon emissions from making and laying the material.


Once any road has been laid or resurfaced, one of the best ways to reduce carbon emissions over its lifetime is to prolong that lifetime. That means timely surface treatments and swift and long-lasting repairs to any cracks or potholes. Deploying a low-carbon technology, such as that developed by Thermal Road Repairs, to fix potholes and other defects helps lower carbon emissions in operation – and hence the whole-life carbon footprint of a road.


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Thermal Road Repairs: Decarbonising the asphalt repair industry

High output. Low emission. Zero waste. Permanent solution.


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