IN GERMANY. the Regensburg Highway Office is carrying out a complete renewal of the busy Friedenstrasse by the main station, to avoid the formation of ruts or ponding by the traffic lights and crossings.
Contractor Stratebau proposed an alternative two-layer arrangement of a coarse aggregate and deformation-resistant asphalt load-bearing layer (aggregate size 0/45), which has already proved its worth elsewhere in the area. According to the Highways Department, asphalt is more cost effective than laying concrete, can be trafficked more quickly, is of equal quality, and is easier to lay.
Playing a central role is Stratebau's Bomag BW 174 AD, pivotsteer tandem roller with split drums, equipped with the latest Variomatic 2 system. This automatically monitors and optimises the effective amplitude, at the same time raising the quality standard, while on the other reducing the risks from inexperienced roller drivers.
These advantages become particularly apparent with chipping mastic asphalt, because the hot mixing material is immediately compacted with the highest possible amplitude. Fewer passes is a major consideration when the material is cooling rapidly.
Using the Variomatic 2 on the curve of the exit lane is no problem either, as the split drum substantially reduces the risk of excessive shear forces on the asphalt. Variomatic 2 monitors the amount and direction of the compaction force - in other words, a kind of quality control.
If the base being worked is stiff, the compaction force is directed horizontally, and if the base becomes soft it is immediately directed into the vertical.
In Regensburg, the maximum compaction force was applied at the highest stage, to achieve a load-bearing layer with the greatest possible resistance to deformation.