Motorway resurfacing: replacing concrete with solid four layer asphalt cover

The Swiss civil engineering and road construction company, Tozzo AG, demonstrate how they are using an asphalt paver with on-board precision to give a perfect new finish to a stretch of motorway between Berne and Zurich with a solid four-layer asphalt cover.

Asphalt paver machines with on-board positioning system in action on the A1 motorway between Berne and Zurich
Asphalt paver machines with on-board positioning system in action on the A1 motorway between Berne and Zurich

In many other countries, the surface of motorways comprises of three layers of asphalt, but the Swiss even add a fourth layer. Tozzo AG has applied that method on a nine-kilometre-long section of the A1 motorway between Berne and Zurich where the concrete cover developed cracks after 45 years of constant stress. The concrete cover was replaced with a solid four-layer asphalt cover and the heavily traveled section widened to six lanes.

Fixed points and planning data

Together with other partner firms, Tozzo was responsible for a large scope of services ranging from the removal of the concrete pavement, to the earthworks and grading, all the way to the application of the new asphalt cover. However, the company dispensed with conventional surveying and staking entirely. Instead, its construction machinery performed nearly all of the work with on-board precision instruments.

Surveyor, Roger Sprenger, explained in detail how the concept worked: “We don’t use iron and cord anymore at all, but rather we use the fixed-point grid created by the owner together with the digital planning data. The drivers operating our machinery receive all of the Geo-data and planning information via the measurement and control systems. This offers huge savings in terms of personnel and man-hours.”

Line up ensures precision

One after another, the hydraulic excavators form the rough sub-grade, and the tracked bulldozer pushes the sub-base and does the fine grading. Then, three asphalt pavers make their appearance. The lead paver in the middle of the trio, a Vögele Super 1900-2 from Tozzo’s fleet of machinery, was specially equipped for the motorway project.

Resurfacing work taking place on the A1 motorway between Berne and Zurich
Machinery at work on the A1 motorway

Its new fixture – a single LPS unit for elevation adjustment with additional GPS support for controlling the direction of travel – provided the required precision and kept system costs reasonable. “With the machinery control system, we install only the foundation layer and the base course of the asphalt cover,” added Sprenger. “The thickness of the layers formed in this way is already so precise that we can then lay the binder course and the surface course as a floating installation.”

Sometimes, such as on rainy days when the asphalt installation had to be suspended, the project partners used their trio of pavers to form the fine grading. Since all of the Geo-data, positioning data and scheduling data were available, the pavers could switch from one section of the construction site to another very rapidly. That made the overall operation more flexible. Separate tasks can be coordinated with one another on short notice and adverse weather conditions caused fewer delays in the progress of the project overall.

Benefits of this approach

At the time of writing this case study, an interim review showed favorable results. That was the halfway point for the main work of the motorway project. Up to that point, everything had gone according to schedule and all asphalt samples measured within the specified tolerances. Despite high investment costs, Tozzo was confident that the machinery technology used would ultimately reduce the cost of performing the work, because the higher quality reduces the risk of deductions.

This case study was provided by Topcon

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