Soil improvement and stabilization with lime is a technique widely used for roads, highways and platforms construction. Addition of lime improves workability, bearing capacity, mechanical resistance of silty and clayey soils; although not a new concept, it has been practised less frequently in dike construction. Recent research programs led by Lhoist Group, a lime producer, have shown the specific conditions which should be applied in the context of hydraulic structures both for the treatment with lime and placement of treated materials. A series of relevant properties was evidenced, enhancing the real potential of this technique for construction or renovation of hydraulic earthen structures. To confirm those results at large scale, an experimental structure was constructed by CER (Experimental and Research Center) of Cerema, in Le Grand Quevilly/France. The structure consists in 2 full-scale experimental dry dikes, the first one built with 2.5% lime-treated silty soil and the other using the native soil (without treatment). The present paper deals with the results of short- and long-term behaviour of those two dikes through in situ and lab tests (on cored specimens). Both mechanical and hydraulic properties have been investigated. Those contributions show that the lime treatment is a promising technique allowing the valorisation of soils with poor engineering properties and inadequate hydraulic behaviour.