A recent article highlights the growing use of dual-layer concrete paving for highway rehabilitation projects in Germany. The technique places a 20–24 cm structural concrete bottom layer followed immediately by a 5–8 cm exposed-aggregate concrete surface layer. The two layers are paved wet-in-wet, allowing each concrete mixture to be optimized for its particular function. The lower layer can use a less expensive mixture, while the thinner surface layer uses higher-quality aggregates selected for skid resistance, durability, and reduced tire noise.
The approach has been successfully applied on four major German highway rehabilitation projects, including sections of the A1, A5, and A9. One of the projects involved rehabilitation of pavement affected by alkali-silica reaction (ASR). The article emphasizes that the method can reduce construction costs while maintaining high pavement quality because materials are used strategically in each layer. After placement, a surface-retarding treatment allows the coarse aggregate in the upper layer to be exposed, producing the textured, noise-reducing surface characteristic of German concrete highways.
A major challenge is construction logistics, since two different concrete mixtures must be delivered continuously and in precisely the right quantities to maintain wet-in-wet placement. The projects demonstrate how modern slipform paving equipment, automated dowel and tie-bar insertion, sensors, and proportional control systems can maintain pavement geometry and quality while achieving production rates of up to 1,100 m per day. Overall, the German experience demonstrates how combining optimized concrete mixtures, layered pavement design, automated construction, and careful logistics can make concrete pavement rehabilitation both technically effective and economically competitive.
Read more about these exciting projects here: https://www.wirtgen-group.com/en-us/news-and-media/wirtgen/sp-1500-aggregate-concrete-germany/
Photo credit: the Wirtgen Group (https://www.wirtgen-group.com/)