The aim of this works is to promote the co-valorisation and shown the important potential of waste in civil engineering materials. The paper presents the experimental methodology to develop a formulation of road material made from dredged sediment treaty with steel slag, a co-product of the steel industry. The mixes destined to improve the mechanic performance of formulated material. In this study two formulations are considered and compared, where two type of steel slag are used to treat dredged sediment. The methodology of this study consists to three steps (Fig. 2). First, a characterisation study has helped understand the physical-chemical and mechanical properties of used materials. We explored also the environmental characteristics by exploration of potential pollution of used materials. The second step consists to develop a method to determine the optimal mix between sediment and steel slag in terms of packing density of mix. In this part, we studied the packing density of the different mixtures to determine the proportions of mixes with maximum packing density. The experimental results were compared with literature model to prediction of packing density. The last part of this study consists to study the mechanical behaviour and durability of the final materials. In this part, we study the mechanical behaviour in short-term and long-term and durability aspect. (C) 2011 Elsevier Ltd. All rights reserved.