Tracking Compaction

In a fast track construction project, no less than 15 Dynapac compaction rollers are paving the way to complete the first Formula One race circuit in the Middle East; in a race against time for the Gulf Air Bahrain Grand Prix in April 2004.

  • E-Mail
By  Colin Foreman Published  March 23, 2004

Tracking Compaction|~|body.jpg|~|Dynapac compaction units racing to get the track done on time.|~|It is an auspicious date that is set to mark the first Formula One Grand Prix to be held in the Middle East: 04.04.04. But before the Gulf Air Bahrain Formula One Grand Prix can take place a large fleet of at least 15 Dynapac compaction had to do their work, ‘racing’ to complete the 5.414 km track. In addition to being the first F1 circuit in the Middle East it will also be the first race in a desert environment. The contract to pave the 15 – 18 m wide race track was awarded to Bahrain Asphalt in September 2002. In the original ‘scope of works’ contract the contractor was only responsible for the asphalt elements of the track. However, as the project’s main contractor, The Cybarco-WTC JV recognised the competence and performance of Bahrain Asphalt – gained on numerous highways in the Gulf kingdom and the new international airport – it was extended. Today the revised ‘scope of works’ includes laying the tracks sub-base, access roads, ‘short cut’ circuits, a dragster race track, stabilised soil verges, plus track-side drainage and gravel run offs. The new race circuit located in Sakhir, close to the Arabian Gulf University, on a 400 acre site was chosen for its undulating terrain and scenic surroundings. On completion, the 60 000 capacity circuit is predicted to be a leading example of its kind in the world with unique buildings and a circuit which starts in the lush oasis style, surroundings of the pit lane and paddock. It will then run into the stark ‘boulder strewn’ desert, approximately 20 km south of the capital, Manama. The circuit design includes a variety of ‘short cut’ layouts which can be configured to suit any required length for the race track. Computer simulations predict that a lap time for the Formula One cars on the main circuit will be 1 minute 33.63 s, representing an average speed of 210.39 km/h. The track will include a total of 12 bends with the longest straight of 1100 m between T12 and T1 passing the grandstands. Speeds of up to 300 k/h are expected. Another fast section will be along a 700 m long stretch between T11 and T12. At the starting grid the mean level will be 7.45 m rising to a maximum 25 m at T4; representing the highest point on the track. rock blasted Before race track preparation could commence more than 500 000 m3 of rock was blasted and cleared by Bramco. Bahrain Asphalt under its new ‘scope of works’ started to prepare the track sub-base in two layers. A wet mix composition was initially laid to a depth of 150 mm and after compaction, a second 100 mm layer was added. Dynapac CA250 and CA252 compaction rollers working behind the paver and with 50-75 m long passes achieved the specified 100% modified compaction density. The sub-base has been topped with a 70 mm asphalt base course using locally sourced limestone. Throughout compaction, Bahrain Asphalt used Dynapac CC222 and CC322 vibratory tandem rollers plus CP271 pneumatic rubber-tyred rollers. Using a paving pattern specified by the Formula One authorities, the CP271 pneumatic roller made the first pass followed by the compaction rollers with 5-6 vibratory mode passes over 50-75 m distances. Compaction was completed with the pneumatic roller and static mode rolling to achieve the specified 100% modified density. The Dynapac CP271 pneumatic roller is used in conjunction with other asphalt rollers to ensure surface sealing and stabilisation. With an operating weight of 12 400 kg and 5 rubber front tyres and 4 rear, ensuring a wheel load of up to 3 t/wheel, it is able to pave up to 4800 m2/h. On completion of the asphalt base course and the curve edging and drainage, Bahrain Asphalt will lay the binder layer before continuing with the surface wearing course. For the surface wearing course a mix of imported aggregates will be used to provide a blend using UAE, Malaysian and UK materials. From the UAE a mix of gabbro-considered to be one of the world’s hardest aggregates – will be used with Malaysian and UK granites selected to meet specified colour and hardness – both key factors, stipulated once again by the F1 Authority, according to Bahrain Asphalts Project Manager, Stephen Nicolay. The wearing course will also feature an SBS polymer modified bitumen with an above 75ºC softing point so as to remain more durable in the region’s high ambient temperatures of up to 55ºC. To be paved above the binder, the 40 mm thick wearing course will be paved and compacted using ‘hot joint’ techniques laying in continuous echelons with 2-3 pavers and Dynapac rollers to achieve 98% Marshall. The Dynapac rollers will work over minimal 75 m pass lengths. For the wearing course, the Authority stipulated that pneumatic rollers were not permitted. Project Manager, Stephen Nicholay, attributes the ‘hot joint’ as one of the project’s ‘trickiest’ aspects, particularly when working across such a wide track width of 15-18 m. “On the sub-base asphalt course cold jointing was permitted but we took the opportunity to gain experience with ‘hot jointing’ methods. Cold joints are unacceptable for the Formula One body on the wearing course,” he said. “But in reality, it will not be possible to use ‘hot joint’ techniques around the complete circuit. It will therefore be necessary to reduce the cold joints to a minimum,” he added. With an asphalt plant producing up to 2000 t/day and the track requiring 10 000 t, indicates that some joints will be necessary. “We will endeavour to minimise the number and will select the sharpest bends at which to introduce these joints,” said Nicolay. Alongside the track a stabilised soil verge is also being prepared by Bahrain Asphalt. Originally specified as desert fill, it has now been changed to cement stabilised sub-base material. Laid to a depth of 150 mm across a variety of widths between 2 m – 40 m, the verge aids the aesthetics of the tracks slopes and provides a drainage run-off. It also assists when cars go off the trackside. The Dynapac rollers were used in both vibratory and static modes in the specified 3 static – 6 vibratory – 3 static pass operation. For the more confined areas, the contractor was able to use walk-behind 1 t Dynapac LP Series rollers. A series of asphalt ‘run offs’ totalling 70 000 m2 are also being prepared on turns where the cars are considered most likely to leave the track. Laid in two layers – 250 mm and 105 mm – for a final depth of 350 mm, compaction is once again carried out with the Dynapac’s. Additional gravel ‘run offs’ – the largest on T9 covering 6500 m2 – are also being laid using gravel from Oman. A 1200 long x 18.5 m wide drag strip- to cater for the already established and increasingly popular sport of drag racing is also included in the complex. Featuring a 630 m long concrete riding surface with zero gradient and no side fall, Bahrain Asphalt is using a micro-silica 50 N/mm2 concrete mix. pumped Dynapac vibratory screeds in 10 m lengths over a 100 m bay panel are being use over a 9.25 m width. A readymix concrete is supplied to site and pumped into position. In total, Bahrain Asphalt is using three Dynapac pneumatic BT90 concrete screeds. The first unit in Bahrain was used at the new international airport. The Dynapac BT90 screed has been designed to compact level and finish large concrete areas. Up to 25 m of concrete slab can be finished in a single pneumatic screed. At both ends of the concrete strip, 160 mm thick asphalt extensions are being paved totalling 11 100 m2 and incorporating a 1% slope. The complex also features a 2500 m long oval with two parabolic corners around the VIP tower as a test area for sports cars and parades. More than 12 km of access roads around the edge of the track and 1.5 km of ‘short cuts’ will ensure emergency access to any part of the circuit. Bahrain Asphalt took delivery of five Dynapac rollers on 1st August 2003 for the Formula One project from local distributor Gulf Equipment and Technology (GET). These included two CP271 pneumatic rollers, one CC322 double drum roller and two CA250 single drum rollers; complementing the company’s own CA252’s and LP Series walk behind rollers. By late November a further five rollers were also delivered by GET – two CC222’s, two CP271’s and a CC322. In addition, main contractor Cybarco is using a number of its own Dynapac CA250 soil rollers for preparation of the car parks. At any one time at least a further five Dynapac rollers are on rental to supplement the projects compaction fleet. By completion, Bahrain Asphalt and its fleet of Dynapac rollers will have compacted more than 120 000 t of asphalt covering an area of more than 440 000 m.||**||

Add a Comment

Your display name This field is mandatory

Your e-mail address This field is mandatory (Your e-mail address won't be published)

Security code