The latest addition to the successful HD series of articulated tandem rollers from Hamm are the rollers with the "plus" sign, the HD+ 120 and the HD+ 140 . They have been successfully taking over road construction sites in the USA and Europe since the end of 2008. One of the first jobs in Germany was the compaction of a compact asphalt pavement on the A61 Motorway employing the "hot-on-hot" process. In an operation that took five nights, the efficiency of an HD+ 140 VO was put to the test in style.

Anyone who has experienced the brand new Hamm tandem rollers knows: They are the rollers with the "plus factor" because their efficiency exceeds all expectations. Including those of Construction Manager Michael Weirich from Faber Bau GmbH: "This roller does the work of two!" he reported enthusiastically from his experience of the new tandem roller HD+ 140 VO in continuous operation over five nights.

Milling, paving and compacting 1,200 m in one night

A consortium comprising Faber Bau and Eurovia was commissioned to repair the badly damaged HGV lane on the heavily used A61 Motorway between Ludwigshafen and Frankenthal. The traffic on the 5.2 km stretch was to be disrupted as little as possible. Therefore, it was decided to close the stretch from 8 pm every night for one week and to carry out the repair work on the 4.70 m wide lane in sections of just over a kilometre.

This was possible because Faber and Eurovia use the Vögele InLine Pave technology. The surface and binder courses were milled off every night. Directly afterwards the InLine Pave train laid approx. 2000 t asphalt in 2 layers and Hamm rollers provided the final compaction. One lane of the motorway was available again to traffic the next morning thanks to this construction method. Maximum productivity was also necessary in every process step – even in the final compaction.

Oscillation enables dynamic compaction of the thin surface course

The compaction quality delivered by the HD+ 140 was convincing right from the start. The compact asphalt surface consists of a 10 cm thick binder course and a 2 cm thick surface course. The asphalt pack can only be compacted dynamically with oscillation because of the thin surface course. This alternative to vibration patented by Hamm very quickly achieves the required load-bearing capacity because the static load works continuously on the asphalt during oscillation in addition to the dynamic load. Measurements taken on the construction site confirmed this: every pass caused a significant increase in compaction so that the required degree of compaction was achieved after only 3 passes. Construction Manager Weirich confirms with satisfaction: "The final laboratory report showed that degrees of compaction of over 100% were achieved on both asphalt courses on all paving days."

Easier handling produces better performance

It was evident at first glance how user-friendly the machine is. Different drivers handled the new roller during the five paving days. The construction professionals sat in the XXL cab of an HD+ for the first time. The function of all the controls was clear to them straightaway and they were able to operate the machine intuitively. They even needed only one HD+ the first night to complete the entire compaction with ease – although two machines were actually scheduled for the final compaction.

The good visibility conditions received a great deal of praise: "You can see exactly where you are going and you have a great overview of the drums and the construction site", was the enthusiastic response of the experienced machine operators regarding the new 14 t roller with the "plus". The men from Faber Bau GmbH were also impressed by the ergonomically optimised adjustable seat, the convenient arrangement of the control panel and the impressive freedom of movement in the XXL cab.

Increased productivity

The high productivity of the HD+ is also crucial for the positive compaction result. There was no doubt about the efficiency of the articulated tandem roller on this point: the wide offset in crab steering mode simplifies manoeuvring and the bright xenon lighting facilitates night-time working. Last but not least, the larger water tank with a capacity of almost 1,200 litres also increases productivity. It enables working one shift without stopping to fill up.

Positive result

With this machine Hamm has brought a user-friendly "powerpack" onto the market. "Normally, we would have needed two machines for compaction for this job. But the HD+ 140 from Hamm compacted the thick asphalt pack quite easily on its own in only three passes", according to Weirich. This confirms what Hamm promises: "HD+: more than you expect!"