Loess is a geological formation with poor geotechnical performances. To upgrade and allow use of this kind of material in civil engineering projects, it is common to add few percent of hydraulic binders. However, the mechanical properties of those materials are often estimated. Their performances are thus sharply downgraded during structure design processes of road structures and their uses are generally limited to the capping layer. However, it is possible to measure accurately mechanical performances of these materials to use them in subbase layers of pavements. Based on results, a design has been proposed and implemented on a real scale test section. The test has been instrumented with strain gauges and preliminary results are presented.