USE OF TREATED DREDGED SEDIMENTS AS ROAD BASE MATERIALS : ENVIRONMENTAL ASSESSMENT

摘要

The treatment and the valorization of polluted dredged sediments is an important issue. The main benefit is the saving of natural resources and the prevention of storage in landfill. The valorization of sediments into road base materials leads to determine characteristics of these materials mainly assessed using mechanical and leaching tests. The Novosol. process has been used to treat the dredged sediment and consists in the stabilization of heavy metals using phosphate and the degradation of organics by calcination at 700℃. The characterization (chemical, physical and thermal) carried out on the treated sediment shows that it is mainly composed with fine particles. The analyses have shown a low bulk density in comparison to that for standard sand. A significant total metal content and the absence of organic matter have been concluded. To evaluate the mechanical behavior of the road materials, tensile strength and elasticity modulus have been measured. It has been seen that the introduction of treated sediments in materials treated with hydraulic binders improves the tensile strength. An environmental assessment has been made on these hydraulic-binder-treated materials thanks to a percolation test and the EN 12457-2 leaching test. The percolation test allows to evaluate the behavior under accelerated conditions. The standard leaching test is used in order to assess pollutant potential. Both tests show that the release of metallic elements is almost the same for mixtures with or without sediments. The results suggest that the use of treated sediments in road materials is not harmful and brings mechanical benefits.