Clear the Ring on the A99

Two SUPER 1800-2 with SprayJet Module rehabilitate one of Germany‘s busiest motorways

In the years to come, the focus of roadworks in Western Europe will increasingly shift from construction of new roads to rehabilitating the existing ones. In Germany alone, a network of asphalt roads spanning more than 60,000km has to be maintained or repaired. In this context it is only logical that both contract-letting authorities and contractors are more and more looking for cost-effective alternatives when it comes to pavement rehabilitation. One such example was Munich‘s A99 ring motorway. German contractor Stratebau was awarded the pavement preservation contract for a 4.5km stretch of the busy motorway. They paved a thin overlay on spray seal, hot on hot.

Paving thin overlays on spray seal, hot on hot, is a cost- effective method for rehabilitating wearing courses and restoring a pavement’s skid resistance. The process is appropriate for all classified roads, especially highly trafficked ones, such as the A99. High initial and long-term skid resistance, less water spray on the road when wet with rain and reduced rolling noise generated by vehicles are just a few advantages offered by this method.

Ideal for paving thin overlays: SUPER 1800-2 with SprayJet Module

Paving thin asphalt surfacings on spray seal hot on hot, however, requires special machine technology. Here the VÖGELE SUPER 1800-2 with SprayJet Module is the solution, as this role suits it to a tee. The paver allows the old pavement to be sprayed with bitumen emulsion and new wearing course to be paved in a single pass. As a result, vehicles never pass over the fresh emulsion, as the emulsion film is immediately covered with asphalt. This provides for a perfect tack coat and a perfect bond of layers. The SprayJet concept is based on a SUPER 1800-2 of standard design which, after just a few modifications and in combination with a newly developed spray module, can be used as a spray paver. The idea behind the concept is a double use of the machine. Within a very short time, the machine can be converted back into a paver of standard design, so that to contractors it is available for spray jobs and conventional paving jobs alike.

Small rates of spread, no formation of spray mist

But beyond that, the VÖGELE SprayJet Technology offers other benefits. It, for instance, allows to select a rate of spread ranging from a very small quantity of 0.2kg/m² to a large volume of 1.5kg/m², at pave speeds from 2 to 20m/min. As a result, bitumen emulsion can be metered very precisely and sprayed in small quantities at low operating speeds. As in the system a constant spraying pressure of no more than 3 bar prevails, the formation of spray mist and pollution are reduced to an absolute minimum. Similar results are not possible with previous systems. Thus, the SprayJet concept is a trailblazing innovation in terms of both economy and eco-friendliness. No doubt, therefore, that the SUPER 1800-2 with SprayJet Module was just the right candidate for the A99 rehabilitation scheme.

Full steam ahead for the ring motorway

In order to keep the roadworks as short as possible on the very busy section of the A99 motorway between München Feldmoching and Allach junctions, a seven-day working week was scheduled for the job. Paving inside the 960m long Allach Tunnel could only be carried out at night between 10 p.m. and 5 a.m., so that the tunnel remained open to traffic during the daytime. The thin 1.5cm overlay proved especially useful here, as it cooled much faster than layers of conventional thickness and could quickly carry traffic.

Two SUPER 1800-2 with SprayJet Module working in echelon

Stratebau’s paving team organized perfect job site logistics and left nothing to chance. On account of the tight schedule, two SUPER 1800-2 pavers with SprayJet Module moved onto the site. They worked in echelon and paved the two stips, each 4m wide, hot to hot. On this job, bitumen emulsion was spread at a rate of 0.8kg/m². The quantity of emulsion required to be applied depends on the nature of the base. On open-textured bases, some 0.7 to 0.9kg/m² need to be sprayed, whereas on close-textured bases 0.4 to 0.6kg/m² are sufficient. Inside the Allach Tunnel, where asphalt was laid on concrete featuring a close-textured surface, 0.45kg of tack coat per square metre was enough. On the whole, some 55 tonnes of bitumen emulsion were sprayed on the 4.5km stretch of the ring motorway.

Paving white asphalt in the Allach Tunnel

Asphalt paving inside the Allach Tunnel was for a couple of reasons different from paving as usual. In order to enhance the lighting conditions in the tunnel tube, a white coloured asphalt overlay was paved. This meant that strict attention had to be paid to absolute cleanliness, as residues from black asphalt would have immediately soiled the thin wearing course. Another circumstance rendering work in the tunnel a bit special was the limited height. The low ceiling allowed only short 2-axle feed vehicles to be used for material supply. These were busy working all the time to feed the pavers with mix and keep the ball rolling. Yet even under these special circumstances, the two SUPER 1800-2 with SprayJet Module worked smoothly and reliably, so that the tunnel could be opened to traffic on time at 5 a.m. every morning.

“The job went like clockwork”

Contractor Stratebau was very satisfied with the job on the A99 motorway. The company had taken delivery of the two SUPER 1800-2 with SprayJet Module just a short time before the job started and no more than three days were left for the paving team to get to grips with the new machines. “Nevertheless, the job went like clockwork,” sums up Operations Manager Hanns Benkert. “The job could be completed exactly as scheduled after five days and two nights. And it was easy to adhere to the specified surface accuracy with a maximum admissible tolerance of 4mm over 4m in the transverse direction.”

Job Site Details
Pavement rehabilitation on the A99 ring motorway between München-Feldmoching and Allach junctions, Germany

Method applied:
thin overlay placed on spray seal, hot on hot Length of section: 4.5km

Paving Details
Pave width: 8m (2 strips of 4m each)
Layer thickness: 1.5cm
Pave speed: 6 - 8m/min.

Quantities Paved
2,500 tonnes of mix (0/5) for thin overlay
500 tonnes of mix (0/5), white, for thin overlay

Emulsion Spread Rates
0.8kg/m² on binder course
0.45kg/m² on concrete in the tunnel
(a total of some 55 tonnes)

2 SUPER 1800-2 with SprayJet Module and AB 500-2 TV Extending Screed
HAMM DV 70 Roller