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  • Writer's pictureSafer Highways

How FM Conway slashed carbon on National Highways M3 job

Contractor FM Conway has used recycled materials to achieve carbon savings on National Highways’ resurfacing of the M3 motorway in Hampshire.

Overall, the use of recycled materials saved 37% of carbon compared to the standard mix.

There are a number of factors which contributed to the carbon saving, with the recycled mix containing 118.27t of carbon, compared to 154.46t in the standard mix.

Standard practice limits the recycled content of surface courses for motorways and major A roads to just 10%, but the material used on the M3 consists of 70% recycled materials in the base course and 50% in the surface - the highest level of recycled content ever user used on the strategic road network.

This recycled material “obviously doesn’t have the same carbon value” as the standard mix, FM Conway head of carbon and environment Vanessa Hilton explained.

“We also used warm mix,” she said. “Asphalt is generally mixed at 180 degrees, but this was mixed at 130 degrees. So immediately you have a carbon saving because we use natural gas to heat and dry our aggregate.”

It comes after National Highways published its net zero strategy, which sets a target of offsetting all carbon emissions from maintenance and construction programmes by 2040.

The plan largely focuses on the use of materials – in particular the  asphalt, cement and steel sectors. A modest 0-10% reduction in carbon emissions is expected to be achieved by 2025 (compared to 2020). That increases to a 40-50% reduction by 2030 (against 2020).

FM Conway business development director Nick Burman emphasised that the 37% saving on the M3 scheme is “virtually at that 2030 target already”.

He added: “It shows that it’s possible. There are quite a few things that need to be done for this to become mainstream but it shows it’s possible.

“If we can keep increasing the material savings and get reductions in fuels and emissions from the equipment then the future looks good. But we’re not quite there yet.”

When it comes to materials, however, there are some limitations.

“You want to put in as much recycled material as possible but there is only so much to go around,” Hilton said. “You might need to prop it up because there isn’t enough recycled material.”

On the M3 scheme, the recycled materials were taken from a previous resurfacing project - also on the M3. They were stored, processed and then mixed through a parallel drum asphalt plant, before being laid back onto the M3 as part of the new surface.

This reduced the use of both primary aggregates from a quarry and bitumen from a refinery, and gave a new lease of life to materials already used on the motorway. The resurfaced section will be monitored regularly to measure the performance of the material.

Access to the RAP (reclaimed asphalt pavement) material was an important aspect of the work.

“I would love what we did on this scheme to become business as usual but in reality to get to this stage it’s going to need investment from the industry," Burman said. "We were only able to get these high percentages of RAP into the mixes because of the asphalt plants we’ve invested in.

"Most asphalt plants haven’t got that facility. There are about 290 asphalt plants in the country and only six with this parallel drum capability and they all happen to be in the south east.

"The industry will invest but they will want certainty of funding, long-term programmes. We’re moving in the right direction but there’s a bigger picture. That’s what I wanted to do with this scheme – show the art of the possible.”

Other key lessons included better understanding or knowledge of the asset, more joined up thinking, and early contractor involvement (ECI).

Burman added: "ECI is key because if you’re in early enough you can look at the designs and methodology. Traditionally by the time a scheme gets allocated to a contractor the focus is on delivery and it’s too late to change anything. On this scheme it was a nine month turnaround so you need to be involved early on."

Overall, Burman and Hilton emphasised that it is time to act, with governments across the world setting climate targets.

“We need to start looking at these things now because it will take time for investment and things to change," Burman said. "And with the targets the government and National Highways have set we need to be cracking on now."

Hilton added: “There’s never been a better time to highlight this – there’s so much support from the youth of today. It is such an important point and people want to see action.”

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