Construction Equipment Great Britain

Volvo P8820C delivers outstanding performance on new Norwich road

The 20km-long Northern Distributor Road at the City of Norwich is nearing completion and a Volvo P8820C paver under Tarmac’s command is putting the finishing touches to the new road.

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The 20km-long Northern Distributor Road at the City of Norwich is nearing completion and a Volvo P8820C paver under Tarmac’s command is putting the finishing touches to the new road.

With eight structures, 13 roundabouts and a total route length of 20km, the Northern Distributor Road (NDR) being built for Norwich County Council, is no small project. When completed, this £178m infrastructure project will create a dual carriageway link that sweeps eastwards from the A1067 Fakenham Road across the northern edge of Norwich City, around the airport to link up with the A47 at Postwick.

As part of the construction process, the NDR project will use more than 150,000 tonnes of asphalt to complete the dual carriageway and the various side roads leading from it. Such a logistical exercise has resulted in the temporary installation of an on-site batching plant to ensure consistency of supply with asphalt materials throughout the duration of the project. And putting the finishing touches to the black top for main contractor, Balfour Beatty, is Tarmac engineering supervisor, Ben Howard and his team, making full use of a satellite-guided Volvo P8820C tracked paver.

“We opted to bring the Volvo tracked paver onto this job for many different reasons,” explains Ben Howard. “We do get tremendous traction and stability from its tracked undercarriage which makes it much easier to push 44-tonne walking floor bulk-trailers when they are in front of the paver’s feed hopper.”

While positive traction enhances productivity, and choosing no-tip walking floor bulk-trailers boosts on-site safety, the P8820C paver also offers a 7.5 - 9.5m adjustable working width for its asphalt screed. And on each of the NDR’s 8.3m wide carriageways, this lets the team deliver on productivity with a forward speed of around four metres per minute, while creating a high-quality finish.

“The variable width vibrating screed lets us lay both lanes simultaneously, without joints or seams,” Ben says. “And a seamless finish is very important for the road’s longevity, which makes it much easier for us to get it right first time.”

While laying both lanes in one pass does boost productivity, it demands a constant flow of hot asphalt to the paving machine. And this is where an on-site batching plant has an important role to play.

“Once we get the go-ahead to pave each section, we can then guarantee a constant delivery of material from our own plant to keep the paver moving until it reaches the end of its prescribed run.” With the road’s sub-base having been stabilised in-situ, the asphalt layers are being progressively built up to achieve the finished profile and gradients required by the client.

“We’re putting down two layers of binder material, onto which a wearing course will be applied,” he says. “These layers comprise a 60mm base, followed by a 55mm binder and a 35mm wearing course.”

Machine control and guidance comes from Topcon’s LPS/GPS to provide a high-quality and stable guidance, so each finished layer provides a very accurate and even surface to accept the next layer. In addition to creating exact layers, the machine also regulates the lateral pitch of the screed box to create the desired fall across the road surface.

Ultimately, such precision will give motorists a smooth, finished road with highly effective surface drainage. “We are working to a tolerance of +/- 6mm at finished road level, which meets Highways England’s specification.”

Using digital design models of the road, Ben Howard and his team load the asphalt paving plans into the machine’s controller via a USB stick. This process avoids the need for traditional conductive roadside pins while simultaneously eliminating a trip hazard from the work area.

In his experience, Mr Howard reports that using machine guidance has been found to speed up the entire paving project, and has made it almost impossible to lay asphalt outside the prescribed area of the road design.

“If the machine is not in the correct location, the plans won’t load and the paver won’t operate using its automatic guidance capability,” he says. “We can operate manually, but using guidance delivers far greater operating efficiency.”

As each layer is laid, the resulting asphalt course is checked immediately behind the screed box with the help of a total station, and then double-checked post-compaction, working on a 10m x 2m surveying grid. “Every step of the process is measured and monitored to achieve the correct end result that is within tolerance,” he says. “We leave nothing to chance.”

The P8820C was added to the Tarmac fleet three years ago, complete with a CBGM (Cement Bound Granular Mixtures) fixed screed. Though the machine’s ability to also accept an adjustable asphalt screed has added operational versatility for the team.

“The Volvo’s vibrating screed is highly effective at laying asphalt and it delivers a 92% compaction rate immediately behind the paver,” he says. “As a result of this efficiency, the quality of levelling is dramatically improved too and we can maintain an even temperature across the asphalt mat to improve the curing process.”

He adds that such a high degree of compaction from the paver means there is less work for the smooth drum compaction rollers to carry out. “With the Volvo paver, typically only 5-10mm of final compaction is achieved using the rollers,” he says. “And that means better operating efficiency for us.”

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