AS the battle for the 2009 Formula 1 world championship title rages and the winners of the first races are toasted, pavers and rollers from German contractor Bickhardt-Bau are in a race of their own to provide a perfect pavement both on the new Yas Marina Circuit in Abu Dhabi, and throughout the entire gigantic peripheral area.

More than 6,000 construction personnel have been working flat out in the UAE capital city to complete the circuit and its surrounding infrastructure in time for the Abu Dhabi Grand Prix in November.
The project schedule for the team from Bickhardt-Bau is extremely ambitious. The Vögele pavers and Hamm rollers were dispatched on their journey via container ship from Germany as early as in May last year.
After arriving there, the first task was placing base course and binder course. Paving work on the surface course started in June. A challenging workload, indeed, for the German road building team and the machines from the Wirtgen Group.
The scope of the contract covers the 5.55-km circuit, including pit lanes, paddocks and emergency roads, as well as all access roads and parking spaces. All told, the project in Abu Dhabi involves laying some 950,000 tonnes of crushed stone for base course and surfacing an area of 750,000 sq m with 210,000 tonnes of asphalt.

Super pavers
Contractor Bickhardt-Bau has plenty of experience using pavers from Vögele and the paving team is well versed in their operation. In Abu Dhabi, the team is using two high-performance Super 1900-2 models combined with AB 600-2 TP2 extending screeds. These pavers have numerous features ensuring that the high requirement in terms of quality will be met. Indeed, the quality concept begins at the material feed stage: large, oscillating push-rollers provide that the material supply from the feed lorry into the paver is smooth – a key prerequisite for maximum surface evenness during paving.
It was the high-compaction technology of Vögele that laid the basis for a perfect build-up of layers in Abu Dhabi. Especially for placing base and binder courses, Bickhardt-Bau relied on the high compactive effort of a tamper and two pressure bars installed in the Vögele high-compaction screed. In this configuration, the pavers yielded an excellent pre-compaction of 92 per cent and more.
Explaining the task in hand, Frank Dittrich, site manager of Bickhardt-Bau, says: “There are two main criteria for the quality of racetracks: the polished stone value (PSV) of the pavement surface and the evenness. The PSV is a measure for the resistance of the stone to polishing and is the decisive factor for the non-skid properties of the surface. This is primarily a question of the material used. As to evenness, however, this characteristic of the surface is produced by the pavers.”
The specifications are extremely demanding. The maximum tolerance allowed for evenness is 2 mm measured over a distance of 4 m in the longitudinal direction. “Thanks to the Vögele grade and slope control technology, we already reached the specified evenness to a large extent when placing binder course. And I know that also we’ll achieve a perfect result with the surface course, due to our Vögele pavers,” says Dittrich.
The demands made on evenness increase from layer to layer. Bickhardt-Bau met these high requirements in terms of accuracy through the use of Niveltronic Plus. It combined the Vögele system for automated grade and slope control with items from the extensive range of Vögele sensors for a perfect match.
On the racetrack, 20-m-wide, base and binder courses were on the majority of sections paved in four strips of 5 m each. When paving an 8-cm base course for the straights and wide bends, Bickhardt-Bau installed a tensioned wire on the outer side of the first strip. For the adjacent strips, it used the slope sensor combined with a multiple sonic sensor tracing the previously-paved strip. On the tight bends, a tensioned wire, traced by the multiple sonic sensor, was used for all four strips.

Big MultiPlex Ski
The binder course was paved in three strips of 6.7 m each. This marked the first major appearance of the Big MultiPlex Ski. “You really can’t go wrong with the Big MultiPlex Ski. It’s a fantastic solution,” says foreman Horst Hennighausen about the sensor system from the wide range of Vögele products.
He has already supervised asphalt paving on the Bahrain and Shanghai race tracks. “The measuring concept enables the system to perfectly level out irregularities, all on its own.” This is why Bickhardt-Bau also plans to make the most of the advantages offered by the Big MultiPlex Ski when it comes to paving the surface course.

Screed assist
The team from Bickhardt-Bau availed itself of another useful feature of Vögele pavers, especially when it came to paving on tight bends: the screed assist function. This function reduces the pressure exerted by the screed on the mix being laid. The screed assist pressure can be set separately for either side.
In Abu Dhabi, this technology greatly facilitated laying base and binder courses in the inner areas of the tight bends. In some cases, an angle of 90 degrees had to be paved in just 3 m width. Consequently, the AB 600-2 extending screed was completely retracted and its weight rested on that narrow screed width. In this situation, the screed assist feature with infinitely variable pressure provides for the upfloat force necessary to support the floating of the screed.
During paving, the screed was assisted more on the inner sides of the bends than in the outer areas, as the screed receives less upfloat force on the bend’s inner side due to the slower forwards movement. Thus, in this challenging paving situation, the AB 600-2 TP2 was able to perfectly float on the mix across the full pave width, thus making a significant contribution to the high degree of surface evenness achieved, says Vogele.

Special mix for circuit
The best kept secret in the construction of racetracks is the composition of the mix, so that this is the only information available: on a crushed-stone base, 50 cm thick and spread by graders, 8-cm asphalt base (0/19) was paved. The binder course, laid in a thickness of 4 cm, is aggregate with a maximum grain size of 14 mm bonded with polymer-modified bitumen. For the surface course, a “special mix for racing circuits” was used, based on aggregate with a grain size distribution of (0/11). Some 10,000 tonnes of granite from Malaysia and greywacke from England were shipped. The reason: when using the local construction materials, it would not have been possible to obtain the specified friction coefficient – also referred to as PSV – greater than 57, Vogele says.
The rules that apply to racetracks differ from those for conventional road construction. Geologist Jürgen Mika of Chemisch Technisches Laboratorium Heinrich Hart, Germany, who has been on the job site in Abu Dhabi on a regular basis, says: “If we had used the mix formulae and grain sizes  which are common practice here, we would have been unable to achieve the specified evenness for the binder course. However, after a few trials, we found a mix that gives a far higher degree of surface roughness. Furthermore, the material is considerably more stable during rolling. That was particularly important when compacting the tight bends.”
Paving work for the surface course began in June. In the area of the racetrack, the special mix is being paved “hot to hot”. On the straights, two Super 1900-2 pavers are laying asphalt in 14-m widths. “In order to achieve the specified evenness and quality, are operating at a speed of just 3 m per minute when paving the 4-cm-surface course,” says Hennighausen.
Extra compaction for the final density and sealing of the surface will be carried out reliably and to a high standard of quality by Hamm tandem rollers.
Everything indicates that the finish line will be reached according to schedule, despite the fact that weather conditions in the desert can be quite extreme at times.
“We’ve already had to stop work on a number of occasions due to rain or sandstorms. Yet we are certain that everything will be ready for the start of the prestigious Formula 1 event,” concludes Dittrich.