THIN BITUMINOUS LAYERS OVER CONCRETE PAVEMENTS..

Two test sections were set up on federal motorways with concrete pavement, portions of which are subject to high traffic. Applying a thin asphalt layer 4 cm thick with a stress-absorbing membrane interlayer (SAMI) was to improve the existing condition and the long-time behaviour of the concrete lane. The concrete pavement was rated in the critical joint area by measuring the relative vertical joint movement and the subsidence of the dowelled transverse dummy joint edge. These measurements were repeated on the stone-filled mastic asphalt over an observation period. Due to differences in climate, traffic volume, carriageway condition and layer composition, pronounced cracking developed in one of the two sections (constructed in 1968 and widened in 1975). The other test section, 16 years old, is practically free of cracks. On the basis of low-temperature and tensile tests on specimens, the critical area in terms of crack formation was shown to be over the joints. The four SAMI layers used are on a par. Recommendations are provided for a limiting value of the permissible relative vertical joint movement of the old concrete pavement to be covered and for measures involving the end plates. (orig.)