WIRTGEN GROUP machines complemented one another perfectly during pavement rehabilitation on the A 61 Motorway in Germany
Motorway rehabilitation or extension jobs require the services of several highly specialized players. The modernization of a stretch of the A 61 between Ludwigshafen and Mutterstadt was no exception. The right-hand lane and hard shoulder had to be removed to a depth of 24.5cm and replaced with fresh asphalt over a length of roughly 4.6km. For contractor Schnorpfeil Bau GmbH commissioned by the regional construction authority in Montabaur the job meant “business as usual”. For RoadNews, it was precisely this that made the project particularly noteworthy. No fewer than seven different machines from the WIRTGEN GROUP worked “hand in hand” on this project to renew and widen the A 61. Combining forces, they did an outstanding job in a short space of time.
The following machines got to work on the A 61: a WIRTGEN W 250i cold milling machine and a WIRTGEN SP 25 slipform paver, a VÖGELE PowerFeeder MT 3000-2i Standard and a PowerFeeder MT 3000-2i Offset, a VÖGELE SUPER 2100-3i paver with AB 500 Extending Screed in the TP2 version, a VÖGELE SUPER 1900-2 paver and – finally – a HAMM tandem roller of type HD+ 140i VO.
The complete surface and binder courses, as well as parts of the base course, were removed most efficiently to a total depth of 24.5cm by the new high-performance W 250i cold milling machine from WIRTGEN. The roadway was removed in two layers, as part of the reclaimed asphalt pavement (RAP) was to be reused. The existing surface and binder courses were milled off in the first pass, followed by part of the base course in the second pass.
The cold milling machine
Rapid completion of motorway and airport projects is one of the strengths of the W 250i. The large WIRTGEN milling machine removes asphalt layers up to 35cm deep and hard concrete pavements at a high rate of advance. In addition to removing complete road structures in a single pass, the machine can also mill off individual layers highly economically – as on the A 61 motorway. Thanks to the powerful 1,005 PS output of its two engines, the W 250i is not only distinguished by its high speed and maximum milling output, but also by its intelligent WIDRIVE machine control system and the three variable milling drum speeds. This also ensures that its operating costs remain exceptionally low for a cold milling machine of this performance class. And it has another special feature:
Fuel-saving drive concept
With its Dual Engine Concept, the W 250i combines two cold milling machines in one: a high-performance milling machine operating with the full power of its two engines, and a cost-efficient milling machine in the mid-range performance class which can economically remove softer asphalt surfacings or porous asphalt with the 608 PS output of one of its engines. On the A 61 motorway, the Dual Engine Concept proved its worth during two-layer removal: while removal of the softer surface and binder courses “only” required the power output of a single engine, the full power output was needed to mill off the base course.
The future belongs to recycling
Nowadays, German road construction authorities are obliged by law to promote the reuse of road building materials and to create the necessary conditions to maximize the use of reclaimed material. Since it was planned to recycle up to 50% of the reclaimed material for the new base course of the A 61 motorway, the old pavement was removed layer by layer in order to supply the asphalt preparation plant with mono-material RAP for recycling. For Andreas Lau, Site Manager for Schnorpfeil Bau, the reuse of RAP is the future, as is the cold recycling technology developed by WIRTGEN: “We have our own cold recycler WR 4200 – and it has proved a worthwhile investment! The recycler breaks down and recycles the available material completely and minimizes the amount of virgin material required. This drastically reduces transport costs and speeds up construction work so that traffic is obstructed for a much shorter time.”
The slipform paver
After removing the right-hand lane and hard shoulder in two layers, the invitation to tender also specified an outer concrete strip with mastic asphalt surfacing. Schnorpfeil clinched the deal with an even better idea. Andreas Lau explains: “The bond between mastic asphalt and concrete is not ideal. We therefore suggested to use a slipform paver to place the outer strip right up to the safety barrier. This saves extra space and ensures maximum stability of the strip. If the other half of the road also has to be rehabilitated at some time in the future, there is sufficient space on this side for 4 + 0 traffic lanes. What’s more, by extending the A 61 in this way, we have also prepared it for the project to widen it to six lanes in the future. The outer strip we have built will last for at least 20 years!”
A WIRTGEN SP 25 slipform paver with an impressive range of uses paved the 70cm wide outer strip. In addition to producing all manner of offset profiles, it can also be used for inset paving of concrete in widths ranging from 1m to 3.5m and up to 40cm high, for example. In offset mode, it produces concrete safety barriers up to 2m high, as well as kerbs, channels, water gulleys, shoulders, traffic lanes and cycle paths up to 2.5m wide. The considerable flexibility and versatility of the SP 25 are based on the innumerable configuration options for the formwork and crawler tracks. This ensures high utilization of the machine. The SP 25 is available with either four or three crawler tracks – two at the rear and one at the front. The concrete hopper can be positioned within or beyond the width of the machine, on the right or left-hand side, at any time. This enables the slipform paver and concrete mixer lorry to move parallel with the traffic, without the mixer lorry having to perform risky turning manœuvres.
The build-up of layers
The existing layers were milled off to a depth of 24.5cm. They were replaced by a new 12.5cm base course of AC 32 TS containing 50% recycled material and an 8.5cm binder course of AC 16 BS type stone mastic asphalt SMA. The special feature of this system is that the stone mastic asphalt significantly increases the stability of the binder course. Although considered relatively innovative, this special mix is increasingly being specified in invitations to tender. The surfacing comprised a 3.5cm layer of mastic asphalt MA 8 S. Stone mastic asphalt SMA 8 S was used for the surfacing in sections wider than 4.3m, such as junctions.
The paver and screed team
“Schnorpfeil has a wide selection of VÖGELE pavers in its fleet which we can deploy as required. Used in combination with a VÖGELE AB 500 Extending Screed in the TP2 version, our large paver SUPER 2100-3i proved to be ideal for pavement rehabilitation and extension of the A 61. With widths ranging from 2.55m to 5m, the screed was simply perfect for the required pave widths, which were between 2.9m and 4.3m,” says Andreas Lau, Site Manager for Schnorpfeil, summing up the situation.
The SUPER 2100-3i is one of the most efficient pavers on the market when major challenges, such as motorways, airports and large traffic areas, need to be tackled quickly, producing top-quality pavements. With a maximum pave width of 13m, it is the ideal large paver for construction of wide roads and large traffic areas without joints. Layer thicknesses of up to 40cm are possible. As a paver in VÖGELE’s new “Dash 3” generation offering a whole array of innovative features and functions, the SUPER 2100-3i sets standards in cost-efficiency, eco-friendliness, ergonomic design, process efficiency and occupational safety.
The material feeders
From 2015 onwards, the German Federal Ministry of Transport has specified the use of material feeders for construction projects on federal motorways and trunk roads, so that paving can proceed without interruption. Material feeders were already specified for rehabilitation of the A 61 motorway. Schnorpfeil opted for the VÖGELE MT 3000-2i PowerFeeder, using one Standard model and one Offset model with a conveyor that could pivot through 55°. The Offset model proved absolutely invaluable, particularly at the edge of the road, where the feed lorries were unable to manœuvre on account of a 25cm-deep trench. The MT 3000-2i Offset commands a large range of applications allowing it to be used for a whole variety of purposes. Such as “hot to hot” paving projects with two pavers. Offset technology is also ideal for filling the gaps between motorway safety barriers quickly and economically.
The tandem roller
For high-grade compaction of the base and binder course, Schnorpfeil used a tandem roller HD+ 140i VO from HAMM, which is fitted with a vibratory and an oscillating drum. The surfaces it produces feature absolute evenness. An automatic reversing function ensures that the machine brakes and accelerates without leaving undulations in the roadway when changing direction. High-precision compaction right up to the edge is also a simple matter thanks to crab steering. Meanwhile, the operator always has a perfect view of the drums, the rolled edges and the job site from his panoramic cabin. But the workstation on an HD+ has a great deal more to offer: such as user-friendly operation, a comfortable seating position, extensive freedom of movement and plenty of storage space for documents, refreshments, mobile phone and personal items. Highly efficient oscillating compaction ensures that the tandem roller achieves the desired degree of density very rapidly.
The machines deployed on the A 61 were all on the same wavelength, so to speak: they were all conceived, developed and built with the user in mind. Hardly surprising, for “Close to the customers” is the philosophy of the WIRTGEN GROUP, to which both VÖGELE and HAMM belong. That philosophy is very much in evidence, not only “on board” a large WIRTGEN milling machine, VÖGELE paver or material feeder, but also on a HAMM roller. This closeness to the customer also extends to service matters – in the tightly knit network of Group sales and service companies, the provision of professional applications advice, the exemplary spare parts service and the local service directly on the job site. And that is something you can rely on!
Ludwigshafen am Rhein / July 2015