Long-Term Behaviour of Concrete Pavements in Germany

Until about 1970 in general Jointed Reinforced Concrete Pavements (JRCP) with expansion joints were in use in Germany. In 1965, the highway administration came to be convinced for the first time by theoretical investigations to construct a Jointed Plain Concrete Pavement (JPCP) with short contraction joint spacing of 5 m (federal road B 47). However, expansion joints in a distance of 100 m still have been required due to the fear that blow-ups could be created at high temperatures. The total shift to JPCP was initiated in 1968 by the construction of a 12 km long motorway (BAB A 5 Darmstadt-Heidelberg). In 8 test sections the type of base course (10 cm asphalt and 15 cm lean concrete with and without 3 cm bituminous intermediate layer) and the thickness of the concrete slab with 22 cm and 25 cm was varied. In 1974, two test sections with specially designed concrete pavements without a blanket layer were constructed at the motorway BAB A 81: ?? 24-cm thick concrete pavement on a 18-cm thick insulating course of foamed EPS-concrete; ?? Full-Depth-Concrete structure with the same slab thickness on a 25 cm thick, cement treated base (CTB) on frostsusceptible subgrade. On all test sections intensive measurements were performed immediately after construction and during the service time up to now. These measurements (opening of the transverse joints, deflection in slab interior and at slab edges, temperature distribution, slab curling caused by temperature gradient, step formation at the transverse joints) enable to evaluate the longterm-behaviour of the structures, which is still good or sufficient in spite of existing cracks and increased deflections at the 37 years old concrete pavement B 47. At the BAB A 5 the asphalt and lean concrete base courses demonstrated erosion resistance but the bituminous intermediate layer did not. The use of an insulating EPS base course underneath concrete pavements has proven successful and can be recommended under special conditions. First tests with a fabric as an interlayer between concrete slab and cement treated base (CTB) were performed in 1981, in order to improve drainage behaviour in the slab-base course-interface. A good long-term behaviour can be stated with an alcali-resistant geotextile of about 500 g/m2 (no polyester). The Advantage of this structure is that it acts as a bond breaker and hence no reflection cracking from the CTB can be initiated. Notching of the CTB exactly below the joints of the concrete pavement (which is necessary due to the required high compression strength of CTB for a pavement structure with bond) can be omitted and the danger of erosion of the CTB is reduced. However, due to the resiliency of the about 5 mm thick geotextile the thickness of the concrete slab should be increased by 1 cm compared to the structure without geotextile. In the new pavement catalogue RStO 01 this structure with fabric is standard now. An alternative is a structure with an untreated base of crushed aggregates. In this case the thickness of the concrete slab needs to be increased to 30 cm under very heavy traffic and special care must be provided to ensure water permeability