With ongoing development of the “deep mixing method”, the scope of applications is always widening. Once confined to ground improvement applications (i.e., to ensure stability and reduce settlements of structures on soft soils), use of this method now ranges from cut-off walls to structural elements and retaining walls. Indeed, the execution is easier, with limited excavated material, and costs less than traditional methods. With these new applications, the required hydraulic and mechanical properties of the soil-mixing material have also evolved, and numerous investigations on the hardened material have been carried out. However, properties of the material in a fresh state must be studied too, and particularly its workability because it is essential for continuity and homogeneity purposes. A laboratory program was carried out to determine the workability evolution of the material with increase of cement content. Results show that the material’s workability limit varies greatly with cement content, and that at constant dosage the clay content still controls the evolution of the material liquid limit. Also, this paper shows a method to determine the optimum water content for the deep mixing material, meaning that instructions can be given on site to ensure that optimum mechanical characteristics are reached.