Valorization of harbor dredged sediment activated with blast furnace slag in road layers

International audienceThe valorization solutions for dredged sediment have been the subject of a great number of investigations over the previous decades. In the current present study, treatment of polluted dredged sediment fom the commercial port of Sfax, Tunisia, is proposed. An industrial byproduct (blast furnace slag) was used to bind raw sediment for a reuse in road engineering.Following standards of this field, the raw sediment first was identified and classified according to the French technical guidance. Then an environmental assessment was applied due to the presence of heavy metals. The concentrations were measured on the raw sediment particles so as to control the binding effect on heavy metals. Sediment mixtures consisted of a mix of sand and a blast furnace slag activated with quicklime. Different mixtures were tested and some were proposed for sub-layer applications. The Sfax commercial port raw sediment is considered as a sandy loam with a very low fraction of clay. The measured concentrations of heavy metals exceed the recommended thresholds for cadmium, copper, lead, and zinc. These can induce hazardous effects in the case of their dumping into the sea. On the other hand, the concentrations of the detected elements after leaching tests run on raw sediment samples are very low compared to the thresholds; such results highlight a possible recycling of the raw sediment in subgrade layers without any negative impact. Suitable formulations were deduced for road engineering tests relying on the ratio the California Bearing Ratio index and the immediate bearing index. If the obtained ratio exceeds one, the treated sediment can be recycled and used in road layers