Reuse potential of dredged river sediments in concrete: Effect of sediment variability

Dredged river sediments may potentially be reused as aggregate in concrete production. The variability of dredged sediments has been quantified by measuring their concentrations of heavy metals, several distinct pollutants, specific granular fractions and organic content at various locations in the Seine River watershed over three years (2015-2017). It has been shown that the sediment deposit does not significantly change from one year to the next, while the organic content, which delays cement hydration, concentrates in the finest fraction removable by sieving. Moreover, 30% of sediment volume is mainly sand and readily reusable in the form of concrete aggregate. Various sediments have thus been sieved to coarse aggregates, sands and fines in order to formulate concretes. Substituting 30% of aggregate volume by the resulting coarse aggregates or sands, once depleted of silt and organic matter: marginally affects hydration, extends setting time to just under 3 h, decreases compressive strength by 10%, and increases shrinkage strain by 15%. In contrast, the finest part of the sediment significantly alters these properties, owing to its soluble organic matter and silt contents.