Paper by LEYKAUF BIRMANN from ISCR 10th 2006 Brussels Belgium
Since 2001 the design with an interlayer of geotextiles is a standard structure in the German pavement catalogue RStO 01. Geotextiles shall guarantee uniform, elastic support of the concrete slab, hence reducing stresses due to temperature and moisture gradient, reduce pumping processes and prevent an origination of reflection cracks from bonded base courses without notching them. By ordership of the German Federal Ministry of Transport, Building and Urban Affairs (Bundesministerium für Verkehr, Bau und Stadtentwicklung BMVBS) investigations and measurements were performed to ascertain the behaviour of 8 test routes with interlayers of geotextiles on cement treated base courses (CTB) after a service time of up to 17 years. Under geotextiles, no signs of in-situ erosion were apparent on CTB which had been classified as susceptible to erosion due to their low compression strength and high mass loss detected in erosion brush-off tests. Drilling cores of the geotextiles aged up to 17 years did not reveal any signs of damage, except for minor occurrences on a polyester geotextile with a thickness of roughly only 1 mm. Therefore alkali-resistant geotextiles (no Polyester PES) with a weight of about 500 g/m2, corresponding to a thickness of approximately 5 mm (unloaded) are recommended. Concrete roads with an interlayer of geotextiles are especially recommended for concrete overlays on old concrete pavements, in tunnels and on rigid base courses.