Quality assurance of exposed aggregate concrete surfaces - Investigations on the freeze-thaw resistance of exposed aggregate concrete surfaces during production in cool weather (late autumn) and early release for traffic

Duration: 01.06.2008 - 31.09.2008

With the introduction of the exposed aggregate concrete construction method, the surfaces of road pavements could be improved in terms of skid resistance and noise reduction (tire/road noise) compared to conventional surfaces, e.g. textured with burlap. However, these positive properties can only be ensured if the corresponding exposed aggregate texture of the surface is permanently maintained. With reference to the General Circulars on Road Construction (ARS) No. 5/2006 and No. 14/2006, relevant investigations have already been carried out on the optimization as well as the target-oriented production of exposed aggregate concrete surfaces. Nevertheless, there is a lack of further knowledge about the durability of exposed aggregate concrete surfaces, especially in the case of early stresses on the surface. For early traffic release of concrete pavements, a minimum concrete compressive strength of 26 N/mm² is required in ZTV Beton-StB 07. In particular, concrete pavements that are produced in late autumn at low temperatures and are subjected to frost and de-icing salt stresses only a short time later, i.e. when they are still young, must have a sufficiently high resistance to such frost/de-icing salt changes. Against this background, this research project investigated the durability of exposed aggregate concrete surfaces when produced under late autumn climatic conditions and when released for traffic at an early age under freeze-thaw stress. Focusing on the exposed aggregate concrete surface, the embedding of the coarse aggregate in the surface was examined in particular by means of surface tensile strength tests on frosted and unfrosted specimens as well as the macrotexture before and after the freeze-thaw test.