Six Vogele pavers and numerous other machines from the Wirtgen Group completed the task of rehabilitating the former German military airbase of Frankfurt-Hahn flawlessly, in an impressive round-the-clock operation.
In just a few years, Frankfurt-Hahn has become an important international commercial airport and the fifth-largest cargo hub in Germany. However, some 40,000 flights per year and last year’s harsh winter have left their mark on the runway. An initial section of the runway was rehabilitated back in April 2010 even as the Iceland’s volcanic ash cloud held air traffic in check. In September, no less than six Vogele pavers were deployed in order to finish the rest of the runway. The airport company itself also set its sights high: during the break in air operations, the company planned to replace the navigation beacons, carry out work on the drainage system and repair the edges of the runway. All of this had to be completed more or less simultaneously.
High-precision work at maximum speed was the order of the day, as the plan was to minimise disruptions to flight operations despite the many construction projects. The contract for rehabilitating 65,000 sq m of runway was awarded to a consortium comprising the contractors Bopparder Asphaltbau, Thomas Bau, Faber GmbH and Asphaltbau Hunsrück. They had no more than three days, or exactly 67.5 hour, to complete the job. This called for more than just working round-the- clock in shift operation. Numerous operations also had to be carried out simultaneously. Maximum concentration by everyone involved and perfect logistics were absolutely imperative, as some 150-160 people were working on the job site during peak times.
The fleet of machines deployed for the project was impressive. Seven milling machines, six pavers and a host of rollers were used for asphalt paving alone. Furthermore, there were numerous feed lorries for the supply of mix, plus the vehicles from those companies tasked with the other construction projects. The first to get going were the seven Wirtgen milling machines, which removed the wearing course and binder course to a depth of 14 cm. The milling machines were given a four-hour headstart in order to prepare enough of the runway for asphalt paving. This allowed the first four pavers to set to work while the milling machines were still busy on other sections. Two Super 2100-2 machines worked hand-in-hand with two Super 1800-2 machines.
All four machines came with extending screeds in TP2 version, equipped with tampers and two pressure bars. The pressure bars are the systems installed to achieve the highest pre-compaction. High pre-compaction of base course and wearing course is essential for a perfect pavement structure and, as a result, for a paving result true to line and level. At Frankfurt-Hahn airport, a special advantage of the Vogele technology paid off: the high compaction systems can be switched on and off at the push of a button. This means that the wearing course could be paved all without high compaction. As an alternative, the pressure for the pressure bars was infinitely variable between a maximum of 120 bar and a minimum of 50 bar.
Grade and slope control was a particular challenge as the runway had to be absolutely even and free of irregularities. Here, the paver operators could rely on Niveltronic Plus®, the Vogele system for grade and slope control, which was combined with multi-cell sonic sensors. On this job site, these sensors referenced from the edges of the previously paved strips. The Vogele multi-cell sonic sensors are in a position to perfectly level out even short irregularities in the base. Equipped with high compaction screeds and multi-cell sonic sensors, the team of four pavers placed the new binder course and wearing course in strips, 5-6 m wide, hot-to-hot. As work progressed, even six Vogele pavers were in operation in alternating teams. All told, they laid about 14,400 tonne of mix for a 9-cm binder course and 8,400 tonne of mix for a 5-cm wearing course.
The permissible tight tolerance of ±2 mm over a distance of 4 m could easily be met. The result was a pavement of impeccable evenness also in the areas of the joints, which were made to perfection. A great performance by the contractor’s team was completion of the job within the short period of time considering an amount of almost 23,000 tonne of mix paved. “To lay such a large quantity of mix in just three days, everyone in the team must know exactly what they are doing,” commented Thomas Mayer, Site Manager, Bopparder Asphaltbau GmbH & Co. KG.
Of course, none of these would have been possible without the sterling work done by the fleet of all machines involved. Every minute, the feed lorries supplied fresh mix to the job site that was laid immediately. Two additional Vogele pavers and a number of Hamm rollers were on standby in case of a machine failure, but were ultimately not needed as every machine worked excellently. “That’s why we were able to hand over the job site to the contracting authority one hour earlier than scheduled, despite the narrow time slot of just 67.5 hour,” summed up Thomas Mayer.