Cornwall’s very own china clay mining industry is playing a big part in the construction of National Highways’ major A30 Chiverton to Carland Cross upgrade.
The government-owned company says sustainability and reducing the carbon footprint are key drivers behind construction of the 8.7-mile dualling scheme, and to that end contractors Costain Jacobs and supply chain Aggregate Industries are tapping into natural Cornish materials and a significant investment in local companies.
Larger infrastructure projects typically use millions of tonnes of aggregate – representing a large carbon footprint – but as with other modern-day road building schemes, the A30 project is utilising a by-product from the china clay mining industry.
The residue, known as stent, would normally have no use and be left in white spoil heaps, scarring the local landscape. Instead, the material from the Littlejohns Pit near St Austell is being processed into sustainable secondary sand and aggregate for construction use.
And just down the road, this is now being used as an engineering alternative across the A30 project, not only reducing the embodied carbon but also saving on the transport carbon cost.
Compared to the 5kg CO2e per tonne carbon emission of virgin aggregate, the locally imported material is around 2kg CO2e per tonne, representing a reduction of around 3kg CO2e per tonne of aggregate used.
Added to that, Aggregate Industries has also invested over £4 million in the nearby Melbur Quarry at St Stephen to produce more carbon friendly warm mix asphalt for the new road surfacing.
Fully approved by National Highways, warm mix asphalt is a greener process that has less impact on the environment, with reduced hydrocarbon emissions and greenhouse gases. Due to its lower temperature, it is also safer for construction workers to use.
Warm mix asphalt is produced using temperatures up to 49 degrees Celsius lower than that used for traditional hot mix asphalt so less energy is needed in the heating process, meaning less fuel and a reduction in the plant’s carbon footprint.
Roads Minister Baroness Vere said: “The A30 Chiverton to Carland Cross upgrade will reduce congestion, improve journey times and provide much-needed connection for local businesses.
“By using natural Cornish materials, we are also ensuring the scheme has a much lower carbon impact and provides a further boost to the local community, which is exactly the kind of innovation we want to see as we strive towards a net zero road network.”
Nick Simmonds-Screech, National Highways Project Director for the A30 scheme, added: “We’re already really proud of our environmental and ecological work – we’re forecasting a net biodiversity gain in the region of 20% – and this greener way of working also spreads to our construction methods and material supply.
“We all have a part to play in reducing our carbon footprint and adapting to climate change, and modern road building methods are certainly playing a part in this.
“The move towards warm mix asphalts allows us to not only achieve huge efficiency savings but also reduce carbon as we strive for net zero by 2040.
“Carbon reduction, along with ensuring our roads provide smooth, safe, and efficient journeys for motorists, are key and something we are constantly striving to improve for generations to come.”
As part of its Net Zero Plan, National Highways is committed to reducing its maintenance and construction carbon emissions to net zero by 2040.
The emissions from the maintenance and construction of the National Highways network led to emissions of around 734 thousand tonnes of CO2e during 2020, which are projected to fall to around 350,000 tonnes in 2040, using a carbon management system to embed approaches that minimise emissions, including lean construction practices and the principles of the circular economy.
On the Cornwall upgrade, Costain Jacobs and its contractors are also tapping into local skills and supplies as construction on the £330 million scheme progresses.
Aside from the aggregate and asphalt production, this includes the:
- employment of site managers and engineers from the local area
- use of Devoran Metals for reinforcement on the project
- daily use of a local scaffold supplier
- use of smaller suppliers of timber products
- engagement with local colleges and the Camborne School of Mines.
John Lee, Costain Project Director, said: “It’s been good to tap into local skills and materials, we’re making excellent progress with the construction works and on course for the new road to be open to traffic in winter 2023.
“We’re also committed to working with National Highways and its Net Zero Plan and the use of warm mix asphalts and china clay by-products is playing a big part in the A30 helping to reduce the carbon impact of construction.”
(Picture – National Highways)