A7, Seevetal-Ramelsloh junction and the Horster Dreieck

On behalf of Autobahn GmbH des Bundes, northern branch, PORR transport route engineering renewed 19,000 m² of surface layer made of porous asphalt (OPA) in the direction of Hamburg between the Seevetal-Ramelsloh junction and the Horster Dreieck. The rehabilitation work was completed on schedule during a full closure of the A7 in this section from 8 p.m. on Friday evening until 5 a.m. on Monday morning.

Frequent changes between frost and thaw had damaged the road surface of the main lane and the first overtaking lane over three kilometres to such an extent that only 80 km/h were allowed. In order to keep the disruption to traffic on this busy road to a minimum, all the work, including setting up and dismantling the traffic safety barriers, dismantling and rebuilding the asphalt layer, as well as the final marking, had to be carried out over a weekend in a 24-hour operation.

Tried and tested road repair method

After milling off about five centimetres of the old OPA layer, the surface was cleaned using high-pressure washing. A bituminous SAMI (Stress Absorbing Membrane Interlayer) layer was then applied, immediately followed by an aggregate. This stress-relieving intermediate layer prevents reflection cracks from penetrating from the damaged substrate and also seals the substrate to allow surface water penetrating through the porous surface layer to be discharged to the side in a controlled manner.

The new OPA layer was seamlessly paved across the full width of the two lanes using a widened asphalt paver and a feeder positioned in front of it to ensure a continuous supply of mix. Finally, the road was marked and bituminous joints were used to connect it to the adjacent existing surfaces.

Digital project planning ensures deadlines are met

‘Except in the case of force majeure, exceeding the construction period for contracts like this one is an absolute no-go,’ explains project manager Ralf Brechwald, adding: “That's why we work with a digital project management tool to keep track of all resources and be able to react quickly to changes.” The provision of the necessary It was imperative that the asphalt transporters were not stuck in traffic on the diversion routes. As a precaution, a replacement paver was delivered, set up and kept on standby. It would have been ready for immediate use in the event of a failure of the main paver. ‘Fortunately, we have the option within PORR of flexibly increasing our capacities. A team from our subsidiary PORR Gussasphalt supported us with the asphalting work. This meant we were able to meet the contractual deadlines and the road was opened to traffic on time,’ adds Brechwald.