For the first time ever, a high compaction screed with a pave width of 15.5m was used on Germany’s Berlin Ring motorway.
Autumn 2014 marked the beginning of a new chapter in the history of road construction: for the first time ever, binder and surface courses were paved over a width of 15.5m using a high compaction screed in the TP1 version. The result: a homogeneous high-quality pavement over the full width of the roadway – as proved with the aid of thermal imaging. An exciting event for all concerned, this première took place on a 4km stretch of the A 10 motorway around Berlin – the so-called Berlin Ring. With a total length of 196 km, this motorway ring is the longest in Europe.
Tenders were invited directly by the German Federal Ministry of Transport. The requirement was clearly specified: jointless paving over the complete road width of 15.5m. The first objective was to prove that top quality can be achieved, even over exceptionally large pave widths. The second objective was to prove that a virtually constant temperature can be maintained in the asphalt mix between the asphalt preparation plant and the screed when using a modern process chain.
Requirements such as those specified for this pavement preservation project for the A 10 will become commonplace in future. This is because new asphalt paving regulations have applied since 2015. A constant temperature of the asphalt and an uninterrupted paving process are two key issues for road construction professionals.
As a result, thermally insulated dump boxes are now mandatory when transporting asphalt by lorry, for simple insulated tippers cannot guarantee that the required temperature will be maintained. The asphalt must be at a uniformly high temperature, without cold areas in corners, bends or along the sides. A second requirement which came into force in January 2015 concerns the use of material feeders when building or rehabilitating federal trunk roads. It applies to projects involving a continuous asphalt paved area of 18,000m² or more.
In this respect, the rehabilitation of the 4.2km stretch of the A 10 motorway must be considered a pilot project. But it is also a prime example of effective collaboration between four companies, from project planning to handover: Oevermann and Faber, Werwie and VÖGELE.
Superlative paving team
Laying a jointless pavement 15.5m wide calls for some seriously large equipment – this was clearly a case for “super machines”. The machines deployed on the A 10 motorway were real giants. WMH Werwie Maschinen-Handels GmbH provided the VÖGELE SUPER 3000-2, the world’s biggest paver with a laydown rate of 1,600t per hour. It was combined with a SB 300 Fixed-Width Screed in the TP1 version with tamper and one pressure bar for high compaction. Not to mention the extra material hopper with a capacity of 24t for the paver. To ensure a continuous supply of mix for the paver, Oevermann provided a VÖGELE PowerFeeder of type MT 3000-2i Offset.
For paving without interruption
In the complete system comprising material feeder and paver, the PowerFeeder MT 3000-2i Offset can stock up to 45t and transfer up to 1,200t of mix per hour. In combination with the paver’s extra material hopper, this means that a 25-t feed lorry can be emptied completely in the space of just 60 seconds. It also means that the SUPER 3000-2 is always supplied with sufficient mix. Non-stop paving was assured.
Robust sensor-based distance control is the most important technical requirement for non-contacting transfer of material to the paver: the VÖGELE PowerFeeder is consequently fitted with a system of three individual laser sensors. They are located on the underside of the pivoting conveyor. This ensures that the distance between material feeder and paver remains constant even when one or more sensors are covered, for instance by passing workmen. The sensors not only prevent the feeder colliding with the paver, but also relieve the paver operator in general so that he can direct his full attention to the transfer of mix.
However, the interaction of man and machine is also crucial. The VÖGELE PowerFeeder features the modern ErgoPlus operating concept. The view from the driver’s seat is excellent. As is the simply structured operating console, which minimizes the risk of operator errors. Instead of numerous different consoles, the paver operator has just one central, intuitively operated control console.
Speaking of intuitive: a joystick allows the pivoting conveyor of the PowerFeeder MT 3000-2i Offset to be moved precisely and with top precision up to 55° in either lateral direction as well as up to 23° vertically. Such precise manœuvrability can yield several advantages. These include safe and effortless feeding of pavers from the side, backfilling of trenches or filling the cavities in safety barriers during motorway construction, as well as reconstruction measures on hard shoulders.
Thermally homogeneous mix
A constant temperature of the mix is just as important as its continuous supply. This is where the feed concept of the VÖGELE PowerFeeder comes into play – a concept geared entirely to ensuring gentle handling of the mix and avoiding superfluous transfer points.
1. Conical augers homogenize the mix
First measure: The specially developed transverse conical augers installed in the VÖGELE PowerFeeders allow the entire mix, transferred from the feed lorry to the material feeder, to be continuously fed into the paving process. The conical shape of the augers also effectively homogenizes the material. Colder parts are uniformly mixed with warmer parts.
At the same time, the conical augers also provide for mechanical homogenization of segregated mix from the lateral areas of the feed lorry supplying asphalt to the material feeder.
2. Heated, trough-shaped conveyor minimizes temperature loss
Second measure: The homogenized mix is then gently transferred to the extra material hopper in the paver by a trough-shaped conveyor belt. Modern diesel heating in the conveyor system ensures that the conveyor is immediately warmed as soon as the machine starts, preventing mix from sticking to the belt and also preventing segregation. This way, the risk of segregation often observed when conveying the mix by bar feeders, is almost eliminated in the VÖGELE PowerFeeder MT 3000-2i Offset.
3. Extra material hopper in the paver optimizes the flow of mix
Third measure: From the trough-shaped conveyor, the mix is transferred to an extra material hopper in the paver which has been optimized to make the flow of material as smooth as possible. For the various paver types, VÖGELE offer extra material hoppers holding from 10t to 25t. These are designed without corners or edges so that mix cannot stick. As a result, there is no risk of cold asphalt lumps being fed into the paving process. Inside the paver, the material is then evenly spread by augers. The thermal image shows an optimally homogenized mix over the entire conveyed distance, from the start up to the paved state.
4. The result: asphalt is thermally and conical augers mechanically homogenized
The uniform temperature curve in the thermal image shows the perfectly homogenized material after paving. All technical measures of the VÖGELE material conveying concept have been carefully coordinated. They ensure that the asphalt is delivered in an optimum condition for paving, avoiding any notable loss of temperature. However, technology from VÖGELE prevents not only thermal, but also mechanical segregation: two aspects that complement one another perfectly in VÖGELE machinery. For the best temperature distribution can only guarantee a durable road if the grain size distribution in the mix is optimal, too.
Top pavement quality over the entire pave width
Only one paver in the world is currently capable of handling pave widths of 15.5m without joints: the VÖGELE SUPER 3000-2. For the Berlin Ring project, this VÖGELE flagship was rented from the company WMH Werwie Maschinen-Handels GmbH. Matthias Beckmann, Werwie, briefly summarized the situation: “The SUPER 3000-2 can build motorways and other large areas with pave widths of up to 16m without joints. Due to its extremely powerful performance, however, it is also ideally suited to roadbase construction. The paver reliably places layers up to 50cm thick in a single pass.”
The robust SUPER 3000-2 can additionally be reinforced with an optional Heavy-Duty Kit when predominantly working with highly abrasive, non-bituminous materials. As usual when working in large widths, the big paver was controlled by an automated steering system with sonic sensor to keep it precisely on course on the Berlin Ring. For this purpose, the VÖGELE automated steering system traced a wire tensioned along the safety barrier as a reference and steered the paver in accordance with the measured data. As a result, the operator was able to focus his full attention on non-stop paving.
The SUPER 3000-2 was teamed with an SB 300 Fixed-Width Screed in the TP1 version, which covers a wide range of pave widths. These extend from 3m in the basic width to 16m with bolt-on extensions. Both fixed extensions of various lengths and hydraulic extensions are available. For the Berlin Ring project, the SB 300 TP1 had been configured for its maximum width. Flexibility was assured by hydraulic extensions on the right and left-hand sides, each capable of being extended by 75cm. What’s more, the SB 300 TP1 was set up in record-breaking time.
A key factor for high-quality pavements and durable roads: the screed was fitted with a TP1 high compaction system comprising tamper and 1 pressure bar. In order to optimally support compaction and produce a smooth surface texture, all compacting elements in VÖGELE screeds are heated across the full screed width.
Dirk Lohne, Senior Site Manager, Heijmans Oevermann GmbH, recalls: “The issue bothering the paving team from the outset was: can we achieve a homogeneous pavement quality over the full width of 15.5m?”
Their concern was not unfounded, for this was the first time that such a pave width was to be realized with a high compaction screed. Even before the paving process was complete, thermal imaging delivered proof of the method’s resounding success. The various thermal images taken while paving the binder course speak for themselves. They clearly show the total thermal homogeneity of the asphalt over the full pave width of 15.5m, without any tendency to segregate.
Top-quality pavements without joints for homogeneous, extremely resilient and durable roads can also be produced in exceptional widths. In such a case, however, the various measures designed to ensure a consistently high temperature in the asphalt and a consistently high mix quality must be coordinated perfectly, from the asphalt preparation plant to the screed.
Among other things, these include: feed lorries with thermally insulated dump boxes, material feeders with a feed concept preventing both thermal and mechanical segregation and screeds with electrically heated high compaction systems ensuring uniform precompaction over the entire pave width.
Job Site Details
|Rehabilitation of the binder and surface courses over a width of 15.5m on the A 10 motorway, Germany|
|Length of section:||4.2km|
|Width of section:||15.5m|
|Layer thickness:||binder course 8cm|
|binder course 5cm|
|Binder course:||asphaltic concrete AC 16 BS 25/55A GW RA|
|Surface course:||stone mastic asphalt SMA 11|
|VÖGELE PowerFeeder MT 3000-2i Offset|
|SUPER 3000-2 with 24t extra material hopper and SB 300 Fixed-Width Screed in the TP1 version|
|Tamper speed||35 – 40%|
|Speed of conveyors||45%|
|Speed of augers||82%|
|Pressure for the pressure bars||70 bar|