Wirtgen Group machines delivering new runway for German airbase
First publishedin World Highways
Compaction was achieved using Hamm equipment
Machines from the Wirtgen Group are carrying out an important reconstruction job for the surface course at Büchel Air Base. Road machinery from Hamm, Vögele and Wirtgen as well as asphalt plants from Benninghoven have been carrying out the work, delivering a new runway within a tight timeframe.
To achieve this, the work had to be planned well in advance, with the contractors organising the logistics and their personnel accordingly.
The air base had a strong need for the new asphalt surface course on its runway. Tornado strike aircraft take off and land roughly 200 times/month at Büchel Air Base, while it also used frequently by large transport aeroplanes.
After more than 10 years of service and several harsh winters, signs began to emerge that there was a growing risk of foreign object damage (FOD) on the runway. This is the damage sustained by aircraft engines when they ingest small items, with mineral particles from the asphalt posing an increasing risk at Büchel.
When loose particles measuring up to 50mm in diameter were occasionally found on the runway in Büchel, planning started immediately for reconstruction of the roughly 45mm-thick asphalt surface course with its 55mm overlay of anti-skid material. The Brenner engineering office in Hennef, Germany, considered several possibilities during the planning process. In the end, the firm opted to reconstruct the surface course with stone mastic asphalt. Compared to conventional materials, stone mastic asphalt offers much better non-skid properties, is durable and highly resistant to deformation.
Asphalt removal The first step was to remove the damaged asphalt surface in two passes, using Wirtgen cold milling machines. The first 5–10mm of the asphalt was interspersed with an anti-skid material and had to be disposed of separately. For this reason, the top layer was removed to a depth of 10mm using super-fine milling, taking out the anti-skid material and minimising the quantity of special waste. This was achieved using two Wirtgen W 210i milling machines, both fitted with micro-fine milling drums featuring 1,008 cutting tools distributed over a milling width of 2m.
Accurate levelling is essential for a precision job and the firm’s LEVEL PRO automatic levelling system ensured that the milling depth was maintained accurately. The system adjusts height using four lifting columns at the front and rear crawler tracks, which are interlinked hydraulically. Should one crawler track run over an elevation or a depression, the other tracks automatically compensate for the difference in height, ensuring that the machine adapts to ground conditions.
The mix was supplied to the necessary tight specification using a Benninghoven asphalt plant
The two large milling machines, each with an on-board power rating of 537kW, achieved a production rate of roughly 25m/min. A larger W 250 cold milling machine then followed, almost matching them for productivity and cutting a milling width of 3.8m. This removed the remaining asphalt surfacing to a depth of 35mm in a second pass. All three milling machines feature twin diesels, with one engine is in operation continuously providing drive for all functions and the second activated when required.
One challenge was to ensure a sufficient supply of water. The water is injected into the milling chamber to bind dust and cool the cutting tools. Each of the large milling machines comes with two separate water spray bars. The water pressure adjusts as a function of load and the water quantity is infinitely variable for optimal cooling of the cutting tools. Around 60,000litres of water were needed/day for the three milling machines – a large quantity. When all 103,000m² of asphalt surfacing had been removed after just four working days, the Vögele pavers and Hamm compactors were then brought in to pave and compact the new surface course.
The general contractor Juchem Asphaltbau brought two Vögele SUPER 2100-2 and SUPER 2100-3i pavers, each fitted with a SB 250 TV fixed-width screed set to 11.5m. To deliver a continuous flow of material and achieve optimum paving quality, a Vögele material feeder was working in front of each paver. The newest of the pavers, the SUPER 2100-3i, had only just been delivered to Juchem Asphaltbau and Büchel Air Base was its first job. This machine was able to pave the surface course on the outer right-hand strip of the 2.3km runway in one day. On the second day, both pavers began working, each being supplied by a Vögele material feeder.
Hot to hot The paving crews laid down the surface hot to hot, at productivity rates from of 2.5–4m/min. This allowed the laying of a quasi-jointless asphalt pavement to a width of 23m. A pavement without a centre joint is of great importance for the durability of the surface course in the central part of the runway, where it is exposed to greatest load. The final job for the SUPER 2100-3i and its material feeder was to pave asphalt on the outer left-hand strip to a width of 11.25m. The result was an asphalt pavement 46m wide with a constant transverse slope of 1.4%, featuring only two joints located away from the critical centreline.
The combination of paver and material feeder can play a crucial role in delivering a high quality paving project using large quantities of asphalt. A Vögele MT 1000-1 feeder and a more recent MT 3000-2i were used at Büchel. The latter unit was supplied by rental firm Werwie, along with a SUPER 2100-2 paver. This heavy-duty material feeder has an impressively large holding capacity: together with the paver, up to 40tonnes of material can be stored.
Fixed screeds set to a paving width of 11.5m were used on the pavers
Controlling the distance accurately between the paver and feeder is important and this is achieved automatically by three laser cells mounted underneath the conveyor. This is assisted by an anti-collision system and should there be a risk of the machines colliding, the paver is brought to a halt immediately, preventing any impact.
Compaction for the job was achieved using 10 Hamm rollers working behind the two Vögele pavers. For this job, Juchem and Werwie opted to use articulated rollers of the HD+ and HD series with operating weights of 9-12tonnes, four of which were equipped with oscillating drums.
Matthias Beckmann, rental park manager at Werwie said that the large, heavy rollers from the HD and HD+ series used in Büchel offer a high performance/unit area. The machines are said to benefit from wide drums with large diameters, powerful drives and a sophisticated automatic reversing function. Meanwhile large tanks for fuel and water are said to allow operation for an entire shift without a need for refilling.
Short time-frame For this project, large quantities of asphalt had to be produced in a very short time. In Büchel, three Benninghoven mixing plants owned by the Juchem Group produced 10,000tonnes in four days. While the two pavers worked simultaneously, each of the mixing plants in Ürzig and Niederwörresbach prepared some 140tonnes and the plant in Boppard some 160tonnes/hour.
The three mixing plant supervisors were in contact with each other all the time throughout the four days to ensure that the two high-performance pavers were continuously supplied with the required quantities of mix. The logistics required up to 50 trucks to be in use, while the three plants coordinated working to ensure the mix was homogenous and met the tight specification.
Juchem used raw material from the same quarries at all three locations and carried out numerous checks. The modern controls used at the plants meant that all three were able to produce the required mix, while also lowering energy consumption.
After two weeks using the machinery and plants, contractor Juchem completed this demanding project, from milling through to paving and compaction, right on schedule. This meant that the Air Base could be handed back to its operators.