Tracing its roots back to the first application in Ohio in 1891, two-layer concrete paving has steadily gained momentum across Europe, maturing from early regional trials into a primary technique for modern Belgian and Austrian motorways. A recent article by Luc Rens in the Revue Générale des Routes et de l’Aménagement (RGRA) revisits the historical trajectory and core engineering principles behind this method, which superimposes two distinct concrete formulations within a single pavement structure. By using recycled or lower-grade aggregates in the thicker base layer while reserving high-grade, exposed aggregates exclusively for the upper wearing course, the technique successfully pairs high-level surface performance with material efficiency and sustainability.
In addition to resource optimization, two-layer concrete offers significant functional advantages, including superior surface smoothness from a finely finished top layer, increased skid resistance, reduced tire-road noise due to smaller surface aggregates, and enhanced durability against severe freeze-thaw cycles. Rens draws on three decades of Belgian field experience with continuously reinforced two-layer concrete to examine technical takeaways on cracking management when utilizing recycled aggregates. These practical insights have informed standard Belgian specifications such as SB250 and CCT Qualiroutes, which now offer concrete guidance on layer thicknesses, aggregate sizing, cement content, water-to-cement ratios, and air-entraining agents to guarantee long-term performance.
Read the article in French here: https://www.editions-rgra.com/revue/1017/international/revetements-routiers-en-beton-bicouche-lexperience-belge-et-internationale