A former Victorian railway tunnel in Northamptonshire has been converted into a supercar test track. New Civil Engineer reports that the 2.7 km stretch of abandoned Catesby Tunnel has been repurposed in a joint venture by Stepnell and Tarmac.

The tunnel was first built in 1897, as part of the route of the Great Central Main Line, which ran from Sheffield to Marylebone Station in London, via Nottingham and Leicester. It was originally conceived as a passenger service, but became more widely used as a coal and goods transportation route.

Most of the route was closed during the 1960s, as other lines such as the Midland Main Line and the West Coast Main Line served the same purpose. However, sections were preserved between Loughborough and Nottingham as a heritage route, and some of the line is to be incorporated into the HS2 route between London and Birmingham.

The Catesby Tunnel was originally going to be part of the HS2 route, but a change of plan led to an application by Aero Research Partners (ARP) for the test track, which was approved in 2017. The track has a stone mastic asphalt surface that was especially designed for the purpose. Tarmac drew on their previous experience working on the Silverstone racetrack.

Tarmac managing director (Midlands) Rob Doody said: “The seamless way this project was planned and delivered resulted in a truly world-class finish that is amongst the highest known paving standards in the world today.”

He added: “The level of paving accuracy has delivered a surface with the exceptional consistency and uniformity needed to meet ARP’s aspiration of producing a world leading aerodynamic test site. It enables automotive engineers to take any surface irregularity out of the equation.”

The track is designed to allow the aerodynamics performance testing of supercars and bikes. Factors such as speed, acceleration times, braking distance, ride, and emissions will be recorded.

ARP director Robert Lewis said: “We have worked closely with Stepnell, who led a professional team of great subcontractors, to successfully complete the civil engineering and building works. The team converted the tunnel from a wet hole in the ground to a pristine running surface that allows sophisticated vehicle testing.”

He added: “The tunnel can accommodate any size of vehicle from road and race cars to HGVs, although the latter could – obviously – not be turned around in the tunnel so would have to reverse out. Our specialist vehicle turn-table can turn around anything up to a long-base transit van.”

The aggregate for the surface was supplied from Tarmac’s Bayston Hill Quarry in Shropshire, which has been used to supply prestigious Grand Prix circuits around the world. The special aggregate has a Polished Stone Value of 65, which means that it has a high skid resistance, making it very much in demand for use on high-speed roads.

Meanwhile, Tarmac have introduced a new ultra-low carbon concrete on part of the HS2 route, Construction News reports. The concrete was used to make floor slabs and walls for a pre-cast in the Chilterns. The factory will manufacture components for the HS2 project. The new mixes proved to be successful, and it is hoped they can be used more widely.

Tarmac head of commercial engineering solutions Robert Gossling said: “Against the backdrop of the climate emergency, this project underlines the clear benefits which can be unlocked when clients and contractors collaborate, in this case engaging to help understand and accelerate the adoption of this new low-carbon concrete solution.”

He added: “Together we’ve shown this new concrete is fit for purpose in slabs and walls, with good repeatability and works with standard production and construction methods. This product is a great step along the industry zero-carbon route map, and the demonstration will help accelerate adoption of this new concrete.”

Tarmac collaborated with other firms, including Sir Robert McAlpine, to produce the concrete, which can be made in standard concrete plants and in regular mixer trucks. Research has already been carried out to prove that the widely used Portland concrete can be replaced with low carbon alternatives in several areas.

Concrete is the world’s second most used material after water, according to the Institution of Structural Engineers. The low carbon concrete is made from up to 90 percent ground-granulated blast-furnace slag, which is used to blend the concrete instead of the more carbon-intensive Portland cement.

Research is ongoing into other ways to reduce the amount of cement required for concrete, such as greater use of admixtures, and using strength-appropriate concrete for the project.

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