Pavement structure has an overall thickness of 130 cm
The new southern runway encompasses an area of 240,000 square metres, impressing with a length of 4,000 m and a width of 60 m. To enable even giant aircraft like the A 380 to land and take off at BBI Airport, a 130 cm thick pavement structure in concrete design was realized both on the southern runway and in all of the other movement areas. In a first step, the 50 cm thick bottom layer, which contained both non-cohesive and cohesive soil, was specifically improved and stabilized by means of cement. The next, 15 cm thick layer is composed of a stabilized mixture of hydrophobic cement and frost-proof sand. The contracting companies relied on Wirtgen technologies also for the completion of these operations: the job was carried out by several WR 2500 S soil stabilizers.
This is followed by a 25 cm thick hydraulically bound base layer. In a final step, the slipform pavers placed a 40 cm thick concrete layer between vertical formwork with sinusoidal cross-section. Planning and realization specified a non-reinforced concrete design with longitudinal and transverse joints. Dowel bars were inserted at regular intervals of 25 cm at the transverse contraction joints, while tie bars were inserted in the peripheral areas of the longitudinal contraction and longitudinal compression joints. In the vicinity of fixtures, such as manholes or foundations, the dowel bars and tie bars were placed on cages. In tapered junctions, in the vicinity of fixtures and in case of geometrically unfavourable slab dimensions, reinforcements were additionally inserted outside the predetermined breaking points to avoid cracking.
High-performance concrete for BBI Airport
Materials and processes needed to meet extremely high quality standards. “We use an air-entrained crushed aggregate concrete of compressive strength class C35/45 that is capable of taking extremely high loads. This material is able to withstand the tremendous mechanical loads imposed by the big aircraft just as easily as the high temperatures generated during landing or the application of de-icing agents in winter,” says graduate engineer Patrick Stryj from becker bau bornhöved (bbb), explaining the choice of material. He is in charge of Europe’s most modern concrete mixing plant in the immediate vicinity of the construction site. In up to six high-performance concrete plants, which are in operation around the clock, up to 11,000 cubic metres of concrete per day can be produced for both pavement and building construction. Cement, sand and aggregate are supplied by rail in order to ease the strain on both the road network and the environment.
Planning right down to the smallest detail
The large-scale project requires a significant degree of logistics and planning. The raw materials needed for concrete production are ordered on the basis of monthly and weekly requirements planning. The specified quality of concrete is then produced and supplied to the paver based on detailed day-to-day planning and current weather forecasts. Up to 50 trucks are available for the job. A quality assurance plan ensures the specified concrete quality by means of several accompanying material tests. These tests include, for example, temperature, water-cement ratio, degree of compaction and air content. Additional tests are performed once the concrete has been placed, such as flexural strength and compressive strength tests.