Use of shells for the mechanical stabilisation of sediments: A valuable geomechanical perspective?

The present study contributes to develop a novel eco-friendly solution for the mechanical stabilisation of dredged marine sediments by using mussel shells, i.e., another highly impacting waste of marine origin, in partial replacement of cements. Which are the underlying chemo-mechanical interactions affecting the evolution of such mixtures? Can the mussel shells replace cement without compromising useful geomechanical and geochemical properties of the stabilized sediments? Can such mixtures still be modelled as soils when it comes to their geotechnical design and analysis? The paper answers these questions by assessing the mechanical performance of the mixtures formed by sediments stabilised with three types of cement and a mussel shell powder and comparing it with that of the same sediments when treated with cement only. Multiple beneficial effects of the use of mussel shell powder, as peculiar source of calcium carbonate for its biogenic origin, have been demonstrated: it acts as a void filler, enhances the electrolytic exchanges between sediment and cement, and increases the contact area between the mineral particles promoting the chemical hydration reactions. As a result, for fixed replacement ratios, the original mixtures still exhibit soil-like behaviour consistent with traditional geomechanics and even better performances than the control mixtures.