Premiere: Two InLine Pave Trains Working “Hot to Hot”
Schedules for runway rehabilitations are always exceedingly tight. And the project at Rostock-Laage Airport was no exception. Here, though, a new approach was taken: two InLine Pave trains from VÖGELE were used to lay a new binder course and surface course “hot on hot and to hot” as a compact asphalt pavement. As a result, German contractor, Kemna Schwerin Tief- und Straßenbau GmbH, not only finished the job at record speed but also delivered maximum paving quality.
FOD – for an airport operator, that is like a red flag to a bull. The abbreviation stands for “Foreign Objects Damage” and describes the danger caused by small objects on the runway – from as little as 4mm in size they can destroy whole aircraft engines. This particular problem had arisen after bubbles – and subsequently cracks as well – had formed on the runway at Rostock-Laage Airport. This meant that large parts of the 2.5km-long runway had to be rehabilitated – and as quickly as possible, in order to minimize the disruption to flight operations.
The ideal solution: the InLine Pave process
“The compact asphalt pavement using the InLine Pave process looked like the ideal solution in this case”, explained Bernd Kanscheit, an engineer at engineering consultancy Mecklenburgisches Ingenieurbüro für Verkehrsbau, Germany. “Firstly, InLine Pave gives you an excellent bond between layers – which prevents bubbles from forming. Secondly, the InLine Pave surface is very dense and low in voids, so neither water nor deicing agents can cause damage. Thirdly, we benefit from the very high compaction of the binder course in the InLine Pave process. It is higher than in conventional paving. That’s particularly important to us here! After all, the characteristic load profile of the take-off and landing runway means we cannot expect post-compaction by vehicles.”
In addition to the requirements on the asphalt, organizational aspects also made InLine Pave an ideal choice. For one thing, the binder and surface courses could be laid rapidly in one pass. Secondly, the pavement was going to be rehabilitated in potentially cool autumn weather. In the InLine Pave process, however, the asphalt stores a great deal of heat. This ensures both correct compaction and slow cooling even at lower temperatures.
95,300 square metres in ten days
Once the go-ahead was given, the road construction contractor had ten days in which to mill off the 95,300m² centre portion of the take-off and landing runway, lay the asphalt pavement with a new profile, apply all the required markings and clean the whole surface. Flights at the airport, which is for both military and civilian use, were suspended during this period.
Before the pavers could get started, four WIRTGEN W 210 Large Milling Machines removed the asphalt. The Kemna team began to place a level regulating layer of asphaltic concrete while the milling work was still going on. Using two VÖGELE pavers of type SUPER 2100-2, they placed a layer 4 – 8cm thick that guarantees water drainage with a slope of 1.5% to each side. The grade and slope control was carried out in the longitudinal direction by tracing tensioned wires.
Kemna was already working “hot to hot” with the VÖGELE pavers. A quasi-jointless strip with a width of approximately 15m was laid on both sides, starting from the middle.
InLine Pave permits a thinner surface course
On top of the very even level regulating layer, the InLine Pave train then laid the binder course together with the surface course in a constant thickness. Unlike the previous pavement structure, the new surfacing is only 2.5cm thick instead of 4cm. “We based our calculations for surface course on the requirements of the German terms and guidelines for the construction of asphalt roadways (ZTV Asphalt StB). The operators of the airport were absolutely delighted with the savings this delivered in terms of surface course material”, Kanscheit explained.
Minimizing the costs of future maintenance operations was also the reason for another technical requirement set by the airport operators: the landing runway was to have no longitudinal joint for 10m to the right and left of the middle, “because experience has shown that the intervals between maintenance operations are the longest then,” said Kanscheit. To meet this demand, he put the compact asphalt pavement out to tender in combination with “hot to hot” paving.
An impressive premiere
Kemna completed the paving works with two InLine Pave trains in just three days. On the first day the teams, each consisting of two pavers and a material feeder, worked in parallel on the outside edges of the landing runway, with each laying a 7.5 m-wide strip. The second day saw the premiere, when the binder and surface courses were placed “hot on hot and to hot” with VÖGELE InLine Pave. A 15m-wide compact asphalt pavement was thus created in a single pass from the middle – an impressive sight that was followed enthusiastically by everyone involved. On the third day, the final asphalt strip, 15m wide, was laid on the opposite side in the same procedure.
17,700 tonnes in three days
The changes in the pave widths of the screeds did not present any problem, because VÖGELE equip their InLine Pave trains with extending screeds. Anything between a pave width of 3m and 8.5m is possible. The screeds are extended and retracted hydraulically. This enabled the Kemna team to lay 5,900t of asphalt on each of three successive working days while meeting the high quality requirements of the customer. “The ‘hot to hot’ joint is as good as invisible”, said a delighted Torben Eymer, engineer and Site Manager. Planner Kanscheit added: “Samples show that there are no structural irregularities in the binder at the joint. And that’s exactly what’s required.”
PowerFeeder MT 3000-2 Offset
Apart from the “hot to hot” paving with the InLine Pave trains, there was another highlight to marvel at on the job site: the PowerFeeder MT 3000-2 Offset from VÖGELE ensured that both pavers were kept permanently fed with material. At a pave speed of around 4m per minute and a pave width of 7.5m, the material feeder delivered some 400t/h of asphalt to the pavers – including some 280t for the binder course and some 120t for the surface course. This performance made a lasting impression.
The material feeder also came up trumps when it came to laying the 3.4m-wide – or should that be narrow – shoulder. “If the mix had been delivered directly by a feed lorry, the existing pavement edge up to the shoulder would certainly have sustained damage. Thanks to the pivoting conveyor, though, the feed lorries were able to drive alongside. Not only did that enhance our quality, it also made us considerably quicker”, said Site Manager Eymer in praise of the benefits of the offset material feeder from VÖGELE.
Kemna was able to wrap up the job within the tight timescale just ten days after getting started. “We thought of everything. The whole job went according to plan”, a satisfied Torben Eymer concluded. After this premiere with a 15m-wide strip paved by the InLine Pave train, he was confident of one thing: “ This technology has a great future, especially for large projects.”
Job Site Details
|Rehabilitation of the take-off and landing runway at Rostock-Laage Airport, Germany|
|Length of section:||1,840m|
|Width of section:||51.80m|
|Pave width:||2 x 15m|
|2 x 7,50m|
|2 x 3,40m|
|Layer thickness:||level regulating course 4 – 8cm|
|binder course 6cm|
|surface course 2.5cm|
|Binder course:||AC 16 B S|
|Surface course:||AC 11 D S|
|4 WIRTGEN W 210 Large Milling Machines|
|2 VÖGELE InLine Pave Trains, comprising: MT 1000-1 and MT 3000-2 Offset Material Feeders|
|SUPER 2100-2 IP Paver with AB 600 TP2 Plus Extending Screed for the binder course|
|SUPER 1600-2 with AB 500 TV Extending Screed or SUPER 1800-2 with AB 500 TP1 Extending Screed for the surface course|
|4 HAMM HD+ 120 VO Rollers|