Whitetopping with Ultra-Thin Layers of High and Ultra High Performance Concrete

For decades, damaged asphalt or concrete pavements in the U.S. were repaired by applying the "whitetopping“ technique. This measure covers the damaged pavement with a new layer of a thickness between 15 and 25 cm, in order to re-establish its viability and safety to traffic. In a research project by the University of Kassel in cooperation with the Federal Highway Research Institute (BASt), it was investigated whether this construction method could be more durably and sustainably realised by using a conventional road paver, if only 6 to 8 cm thick layers of steel fibre reinforced High Performance Concrete (HPC: compressive strength 125 N/mm²) or steel fibre reinforced Ultra High Performance Concrete (UHPC; 180 N/mm²) was used. First, the road construction was dimensioned with a finite-element program. The appropriate thickness of the structure was designed considering the contribution of fibres and the mesh reinforcement and to restrict the crack width to 0.1 mm only to prevent corrosion of the reinforcement. Then the structural behaviour was determined under fatigue load on a model structure in the laboratory. After a sufficient capacity was confirmed, a first test road – a parking lot at the German freeway A2 – was built in 2008.