United Kingdom: SP 25i slipform paver masters a very special job

Wirtgen SP 25i was used on the M6 motorway near Cannock together with a Wirtgen ISF 25i (independent side feeder) in order to pave a concrete slab under exceedingly difficult conditions.

With an overall length of 373 km, the M6 is the longest and one of the most heavily trafficked motorways in the United Kingdom. The M6 connects the M1 motorway near Rugby with Carlisle near the Scottish border. Due to the steadily growing volume of traffic on this major artery, the Highways Agency as customer for the planned construction project decided that the service lane was to be upgraded for use as an additional traffic lane between junctions 10a and 13 near Cannock, 25 km north of Birmingham. The primary task of the consortium comprising Carillion as contractor of the Highways Agency and the construction company Extrudakerb Ltd was to completely replace the existing reinforced concrete slab with asphalt surfacing on the service lane in order to bring the new traffic lane onto a level with the adjacent pavement and create a homogeneous concrete pavement.

Special conditions call for special machines

The exceedingly short time frame during which the concrete slab could be paved on the M6 motorway during the night was never more than six hours.

The exceedingly short time frame during which the concrete slab could be paved on the M6 motorway during the night was never more than six hours.

This unique project is the first of its kind in the United Kingdom. Work can only be carried out on this highly sensitive traffic artery during selected time frames and in exceedingly confined conditions. Following an intensive planning phase, project manager Mark Gladwell decided on a sophisticated timetable and logistics schedule covering every last detail. During the day, temporary steel barriers separate the service lane to be converted from the main traffic stream on the adjacent traffic lane. At night, when traffic is lighter, lane 1 and part of lane 2 are closed to traffic to provide an access route for the construction vehicles. "Such a tricky project can only be carried out with the aid of extremely sophisticated machine technology," says Mark Gladwell. It was decided to use a Wirtgen SP 25i together with a Wirtgen ISF 25i which had been developed on the basis of the SP 25i in order to meet the project's special requirements. Gladwell continues: "Using the ISF 25i as an independent side feeder with pivotable conveyor was the only option available to assure the safety of the operator and of the workers on this confined job site while at the same time minimizing the nuisance to passing traffic."

Always thinking one step ahead

For specific, highly demanding applications, Wirtgen GmbH develops innovative solutions together with the customer so that jobs can be carried out optimally and cost-efficiently. Time after time, two very important factors come into play here: Wirtgen combines sophisticated innovative machine technology with a worldwide service network of Group-owned sales and service companies and selected dealers. For customers around the world, optimum service means short routes. At the same time, it also means that all service activities center around qualified advice from specially trained personnel on site.

In this respect, Wirtgen GmbH offers its customers appropriate solutions for every application, including such unconventional and unique jobs as the M6 project. "We were only able to meet these unique requirements and ensure that this demanding order could be optimally implemented with the special machine technology which was proposed by Wirtgen and then ultimately used for the job," says Dom Egan, Site Manager at Extrudakerb Ltd. The Wirtgen experts' years of experience in practical applications on site proved decisive here. And to ensure that everything proceeded smoothly from the outset, a fitter from the Wirtgen brand headquarters in Windhagen and another from the Wirtgen Group's British subsidiary Wirtgen Ltd were on hand when the job site was set up and on the following days. From then on, the service technician from Wirtgen Ltd. was available on call at any time to support the customer promptly on site whenever needed.

A Wirtgen SP 25i was used on the M6 motorway near Cannock together with an ISF 25i .

A Wirtgen SP 25i was used on the M6 motorway near Cannock together with an ISF 25i .

Paving concrete in challenging conditions

The project as a whole encompassed 16 km of new roadway, approx. 3 m wide and 300 mm deep. Around 14,000 m³ concrete of quality class C50 were delivered to the site just-in-time by Lafarge Tarmac from their mixing plant in Walsall using specially modified 8 m³ concrete mixer trucks. These special trucks are equipped with GPS and an automatic system which monitors and adjusts the consistency of the concrete in order to ensure that exactly the required concrete quality is delivered at the right moment in time.

On arrival at the job site, the concrete is transferred over the top of the temporary steel barrier into the hopper of the ISF 25i and from there to the slab paving kit of the slipform paver via two synchronized conveyors. On account of the special site conditions outlined above, the time frame available for working was never more than six hours. This made it eminently important to maximize productivity within this narrow time frame so that the construction work could proceed efficiently. As a result, around 32 m³ of concrete were paved per hour, making almost 200 m³ per six-hour shift. The work was undertaken in 12 consecutive shifts followed by two rest days. All the other materials needed for the project as a whole, i.e. around 300 t of reinforcement, as well as 25,000 tie bars and 3,000 dowels, dowel bars and curing material, had to be delivered during the night, within the same time frame. Another major challenge, also in terms of the logistics.

Paving concrete on narrow roads or individual traffic lanes is an ideal job for the Auto Pilot Field Rover first presented in 2013.

Paving concrete on narrow roads or individual traffic lanes is an ideal job for the Auto Pilot Field Rover first presented in 2013.

SP 25i with Auto Pilot Field Rover

The compact slipform paver SP 25i is a multifunctional all-rounder for high-grade inset slipforming of narrow concrete roads, individual traffic lanes, minor rural roads and cycle paths. The multi-functional machine's outstanding features include the slipform paver's convenient operation, the high speed at which it can be transported and repositioned and its fuel-saving engine concept. The machine's application-related and economic advantages are unbeatable, however, when combined with the Wirtgen Auto Pilot Field Rover which was presented in early 2013 and won the bauma Innovation award 2013. "Paving concrete on narrow roads or individual traffic lanes is an ideal job for our Auto Pilot Field Rover," explains Martin Datzert, sales and applications specialist for slipform pavers at Wirtgen Windhagen Vertriebs- und Service GmbH.

Good-bye to stringlines

For the first time ever, the Wirtgen Auto Pilot Field Rover has made it possible to produce concrete pavements fully automatically without stringlines. This means that road construction firms can now complete their jobs considerably more easily, quickly and above all economically, as the exceedingly time-consuming job of installing stringlines is no longer required. Stringline-free concrete paving works for a range of very different basic conditions from 3-m-wide pavements for a cycle path to concrete barriers on a motorway. If the concrete profile is to be slipformed on an existing roadway edging, the user can calculate the optimum virtual stringline on site in a matter of minutes. For the first time, the customary stringline can indeed be replaced in practice.

This advantage proved particularly useful for the construction project on the M6 motorway. "Another decisive advantage of the Auto Pilot Field Rover was that we did not have to install stringlines, as the Highways Agency had prohibited the use of posts drilled into the ground for attaching the stringlines. Such posts could have damaged underground cables," reports Site Manager Dom Egan, Extrudakerb Ltd. "What's more, the Auto Pilot allows the machine and job site to be set up more speedily, maximizing the time frame available for paving the concrete. A decisive factor in view of the short time frames specified for the M6," says Egan.

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