North Africa has developed into a boom region. To keep heading for growth, large sums of money are being invested in the gigantic “Autoroute Transmaghrébine”, the biggest road construction project in Africa and currently also in the world. The motorway will link the Maghreb states of Morocco, Algeria and Tunisia over a total length of more than 3,010 km. Construction work has made good progress in Algeria, where three construction consortiums are building around 1,200 km of motorway. The construction gangs include 36 road pavers from Vögele, 30 rollers from Hamm and several Wirtgen slipform pavers.
Three construction consortiums are involved in building the 1,216 km long Algerian section. The stretch leading from Bordj-Bou-Arreridj to the Tunisian border is built by the Japanese consortium COJAAL. A section leading around Algiers is built by ALTRO and COSIDER, two Algerian construction companies. The remaining stretch is built by the Chinese consortium CITIC-CRCC. Further companies are involved in building bridges, tunnels and sewage systems. Total investments amount to eleven billion US dollars in Algeria alone.
High traffic volumes are expected on the North African “lifeline”. The Algerian section of the “Autoroute Transmaghrébine” is therefore built as a three-lane carriageway in both directions. The bar has been set high also regarding the quality of the pavement structure, in particular in terms of stability. All SUPER pavers from Vögele are therefore equipped with high-compaction paving screeds. Yet another important criterion is adherence to line and level accuracy. Levelling systems support the paving teams in working exactly according to plan. For this purpose, the pavers’ automatic levelling system NIVELTRONIC Plus® is combined with either RoadScan® or Big-MultiPlex-Ski, Vögele’s sensor systems. Both systems play their aces when it comes to paving asphalt without using artificial references, such as stringlines or kerbs, making them ideal candidates for new road construction. In order to meet the requirements placed on material quality, the maximum distance of the mixing plants from the paving sites is limited, and the paving mixes are continually checked. The road structure is made up as follows: The base layer consists of cement- stabilized gravel sand and has a layer thickness of 20 cm. It is followed by a 14 cm binder course of bitumen gravel. The layer structure is completed by a surface course consisting of asphalt concrete (0 –14 mm) which has a layer thickness of between 6 to 8 cm.
On its 365-km long stretch of the motorway, COJAAL is relying on twelve SUPER 2100-2 pavers fitted with AB 600-2 TP2 paving screeds, and four additional SUPER 1900-2 pavers equipped with AB 500-2 paving screeds. The three traffic lanes are produced at working widths of 6.25 m each using the “hot-to-hot” paving method. For precise levelling, COJAAL relies on the NIVELTRONIC Plus® combined with the RoadScan® sensor system. The high-tech system works on an electro-optical basis: Data collected by means of optical instruments are processed electronically. In the process, RoadScan® emits laser signals that are reflected by the subgrade and subsequently received by the laser head. The electronic system uses these data to determine the actual elevation of the screed.
Compaction of the separate layers is effected by a veritable armada of Hamm rollers: Among others, 12-ton tandem rollers type HD 120 and 18-ton pneumatic-tyred rollers type GRW 18 are in operation, and can be relied on to produce the specified density.
The Chinese consortium CITIC-CRCC is operating 13 pavers type SUPER 2100-2 on its stretch of the motorway. In contrast to COJAAL, paving is effected across the full width. The paving screeds have been set up to an impressive working width of 12.5 m. Each paver is equipped with high-compaction standard screeds type SB 250 TP2. The SB 250 has a basic width of 2.5 m, and can be extended to a maximum paving width of 13 m by means of bolt-on extensions and hydraulically extending attachment parts. Three compact-class pavers type SUPER 1300-2 are taking care of any additional surfaces along the road, for example, the hard shoulders. The Chinese paving teams are relying on Vögele’s Big- MultiPlex-Ski sensors in combination with the NIVELTRONIC Plus®. This system consists of three ultrasonic sensors fitted to a carrier, which are capable of scanning an area of up to 13 m. Like any ultrasonic sensor, the Big-MultiPlex-Ski is flexible in use and is suitable for equalizing any ground irregularities. The mean values calculated from the readings of several sensors enable even extensive irregularities to be equalized that would otherwise not be recognized as a defect when using one single sensor. The track layout is thus precisely adhered to even without using stringlines.
Contractors COSIDER and ALTRO are working their section near the capital city of Algiers using two pavers type SUPER 1800-2 and two pavers type SUPER 1800-1. All machines are equipped with high-compaction AB 500-2 TP2 extending screeds. The paving gangs are operating their road pavers in 14-hour shifts, and are not paving across the full width but “hot-to-hot” in two 6.25 m wide strips. Here again, the NIVELTRONIC Plus® automatic levelling system is combined with the Big-MultiPlex- Ski for levelling.