Environmental assessment, mechanical behavior, and chemical properties of self-compacting mortars (SCMs) with harbor dredged sediments to be used in construction

Environmental and ecological issues have led to the development of new sustainable channels for the recovery of dredged sediments. One of the major difficulties of sediment valorization lies in particular in its very heterogeneous composition. For example, the presences of heavy metals and organic matter have a significant influence on the environmental impact of materials formulated with sediment. Some heavy metals such as antimony, mercury, lead, and cadmium in high concentrations are dangerous to the body. Trace metals trapped in sediments are transformed through complex biogeochemical processes. They subsequently associate with organic matter to form clay-humic groups that define the degree of sediment pollution. The Harbour Dredging Sediments (HDSs) used were classified as non-hazardous waste in accordance with Directive 12/12/14/EC. The purpose of this study is to evaluate the environmental impact of the use of HDS from active lagoon in the formulation of self-compacting concrete (SCC) with the objective of incorporating a high sediment content, obtaining materials with a low environmental impact and ensuring compressive strength of a C25/30 class concrete. Three HDSs are being studied that have a significant impact their difference by their fines content at 125 μm. Sediments recovered from the active lagooning process have not undergone any physical, chemical, or thermal treatment. The DMDA (Densified Mixture Design Algorithm) method is used to optimize the composition of "sediment" SSCs. The communication focuses on mortars equivalent to these "sediment" SCCs (SCMs). Sediment represents about 20% of the granular composition with a sediment-to-cement ratio of 80%. Compressive strengths are greater than 25 MPa and tensile strengths are in the range of 3 to 8 MPa at 28 days of curing. From an environmental point of view, all heavy metals are stabilized except nickel. In particular, there has been a considerable decrease in the levels of sulfate, total organic carbon, and chloride. The different SCMs are classified as inert, clinker hydration produces hydrates that capture and stabilize heavy metals in the cementitious matrix. The results obtained show that HDSs could be used as a secondary raw material in the formulation of self-compacting concretes.