Urban-adapted pavement based on inverted principles: case study from Rufisque (Senegal)

This study investigates the implementation of a modified inverted pavement structure to rehabilitate Boulevard Maurice Gueye in Rufisque, Senegal—an urban section of National Road No. 1 subject to intense heavy vehicle traffic (907 trucks/day). Inverted pavement systems, characterized by a cement-treated subbase supporting an unbound aggregate base and a moderately thick asphalt surface, offer enhanced performance over traditional flexible pavements, particularly in tropical environments with weak subgrades and high axle loads. A comprehensive investigation was carried out including geometric and structural surveys, geotechnical characterization of subgrade soils, deflection testing with a Benkelman beam, and mechanistic-empirical design using ALIZÉ-LCPC software. Results revealed significant variability in existing pavement layers and subgrade conditions, with some zones exhibiting CBR values as low as 2% and requiring material substitution. The proposed structure—comprising 7 cm asphalt concrete, 14 cm asphalt gravel, 12 cm crushed basaltic gravel, and 20 cm cement-treated lateritic soil—was found to keep all stresses and strains within allowable thresholds. The study demonstrates that inverted pavement systems can provide a technically robust and economically viable solution for urban roads in West Africa, promoting long-term structural performance and resilience under heavy traffic loading. In this urban application, we adopt a modified inverted configuration that preserves the stiffness inversion (cement-treated base confining an unbound aggregate base) while using a moderate asphalt package to ensure intersection shear resistance, waterproofing of the foundation, and mill-and-inlay maintenance without exposing bound layers.