In ground improvement projects by deep mixing, the laboratory experimental programis an important stage by which,the suitable binder and quantity are chosen andgeotechnical performances of improvedsoil are evaluated.In current practice, the design process oflime-cement columns ismainlybased on unconfined compressive strength and the corresponding secant Young's modulusevaluated by unconfined compression tests. In this paper, the main laboratory methods used to assess the mechanical properties of improvedsoil mixed with lime and cement in deep mixing are reviewed. Laboratory preparation of the samples and testing procedures for unconfined compression tests, triaxial tests and oedometer testsare presented. In addition,someexperimental results of tests conducted on soft soils mixed with lime and cement are analyzedand commented.