Evaluating the Impact of Crushing Process on Strength Characteristics and Leachability of Cement-Stabilized Dredged Sediment

Abstract

Stabilization of dredged sediment and reusing the mixture as a construction material is an effective way to reduce environmental problems and save natural resources. However, the crushing process that occurs during construction may affect the mechanical properties and leachability of the reused stabilized soil, an issue that is less reported. Therefore, consolidated undrained triaxial tests and semi-dynamic leaching tests were conducted on stabilized sediments and recompacted crushed stabilized sediment grains (SG) to evaluate the influence of the crushing process. The results of the triaxial tests showed that the stabilized sediment exhibited strain-softening and brittle behaviors under various confining pressures (100, 200, and 400 kPa), while strain-hardening and ductile behaviors were more obvious in the SG. The reduction in cohesion between stabilized sediment and the SG reflected a loss of cementation bonding during the crushing process. The overall leaching behaviors versus curing time of heavy metals (As, Cr, Cu, Zn, Pb, Ni, and Hg) in stabilized sediment was similar to that of SG. The leaching mechanism indicated a good immobilization of heavy metals in stabilized sediment, while their stability in SG was poorer. The reason for the differences in triaxial strength properties and leachability were mainly attributed to the fact that the strong cementation bonding was destroyed by the crushing process, weakening the soil structure and raising the potential for release of elements.