Polluted river sediments from the North region of France: Treatment with Novosol® process and valorization in clay bricks

The paper presents results of studies on the valorisation of polluted river sediments from the North region of France. The first objective of this study is to validate the treatment of polluted sediments with the Novosol® process. This process is based on the stabilization of heavy metals in the solid matrix by phosphatation and the destruction of organic matter by calcination. The results of environmental tests carried out on treated sediments showed that polluted sediments became inert. In addition, the physical characterisations of treated sediments classify them as sandy silt. Thus treated sediments were used as a brick making raw material. The second objective of the study is to determine the optimal mix-design. Four mix-designs were studied with treated sediment ratio varying from 0% to 45%. Physical, mechanical and chemical properties of these bricks were evaluated. The results obtained indicated that sediment proportion is an important parameter in determining the brick quality. Increasing the sediment content resulted in a decrease of brick compressive strength (though it is still higher than that of standard brick) and a decrease of its resistance to freezing and thawing.Leaching tests, performed according to different standards on substituted brick samples, showed that the quantities of heavy metals leached from crushed bricks were within the regulatory limits. The 35% ratio of substitution appeared to be the most effective considering physical, mechanical and chemical aspects.