Paper by VON WILCKEN from ISCR 5th 1986 Aachen Germany
Larger aircraft, heavier lo~ds, in~reasing numbers of load repetitions, but e8pec~ally s~ngle wheel loads of about 33 tonnes have given rise to d~age which has similarly affected airfields all over th~ world. The damage is in part due to the sub-base be1ng too weak and to lack of shear transfer at the edges of the slabs. As a rule, aircraft movements occur in all directions on aprons, so that the latter are most severely loaded at the joints. Experience gained with the H + W slipform paver in building the west take-off runway at Frankfurt airport has been utilized in the construction of new pavements at Düsseldorf and . Cologne-Bonn. This paver is, ~oweve~, of such des~gn that it can also operate on s1de ra1ls. The old form of construction used at Düsseldo~f, which has proved unequal to present-day loading condi~ions, comprised a 3D-em-thick concrete slab on 5 em b1tumencoated gravel and 15 cm stabilized soil. In the new method a 40-em-thick concrete slab rests on a 20-cmthick cement-bound sub-base. Tbe slabs are 3.75 m x 3.75 m in size, laid in a machine operating width of 7.50 m. At the contraction joints, a sinusoidal profile shaped by the concreting forms serves to transmit shear. At the Cologne-Bonn airport , a construction method satisfying the most stringent safety requirements was chosen for a freight apron used only by high pay-load aircraft. The concrete slab is 40 cm thick, installed in two courses consisting of 30 em of gravel concrete (0 - 32 mm aggregate) and 10 cm of crushed stone concrete (0 - 22 mm aggregate). The concrete is of grade B 45 in both courses. The.slabs are 5 m x 5 m in size, laid in a machine operating width of 10 m. All the transverse and longitudinal joints are provided with 30-mm-thick dowel bars. Concreting was done with two slipform pavers on stationary forms. The use of slipform pavers for airfield construction is still controversial. All the same, the li + W slipform paver was successfully used at the airports of Zurich, Munich and Vienna in 1985.