JOB REPORT

Porous asphalt surface absorbs 10 dB.

Paving porous asphalt on the A61 motorway in Germany

Traffic volumes on German motorways have been increasing steadily over the years – and so have noise emissions. At the same time, new residential areas are built ever closer to arterial roads and motorways. This has led to an increasing demand for quiet pavement materials which minimize rolling noises even at high travel speeds. In September 2007, a state-of-the-art Vögele paver type Super 2100-2 equipped with a 12 m wide paving screed type SB 250 played an important part in the construction of a trial section for optimizing the use of porous asphalt: The machine paved four different types of porous asphalt on the heavily trafficked A61 motorway, laying the foundations for a long-term trial.

The trial project had been initiated by Straßen.NRW, the state-owned enterprise responsible for road construction and maintenance in the German State of North Rhine-Westphalia. In the context of a project called “Quiet Road Traffic”, the authority has been involved for many years in the development of new asphalt materials which minimize noise emissions. Four types of porous asphalt in different compositions were selected for the 6-km long trial section on the A61 – the surface course of which was in need of rehabilitation anyway – and will be examined regularly in the coming years for their durability and noise reduction.

Porous asphalt needs to be paved seamlessly across all carriageway lanes to ensure water drainage. The material properties are eminently suitable for large paving widths: High pre-compaction by the paver is desirable for many asphalt mixes, but quite the opposite is true here. The Super 2100-2 paver from Vögele needed to work with minimum vibrating power to achieve the specified void content. The rollers following behind the paver also worked in static mode only. The DV 90 tandem rollers from Hamm succeeded in achieving final density in a few roller passes even without activating their dynamic compacting systems.

It is expected that all four mixes will reduce the noise emission to a much greater extent than other types of porous asphalt: The authority estimates the initial reduction to be between 8 and 10 dB, which equals a decrease by fifty percent of the felt noise level when compared to the previous pavement.