Valorization of Dredged Harbor Sediments through Lightweight Aggregate Production: Application of Waste Oyster Shells

Abstract

The treatment and valorization of wastes such as dredged harbor sediments and oyster shells have become critical for environmental management. In order to promote waste valorization and resource sustainability, this study evaluated the feasibility of using harbor sediments and oyster shells for lightweight aggregate (LWA) production. The effects of the oyster shell content and sintering temperature on the sediment-based LWA properties, including particle density (PD), water absorption (WA), and crushing strength (CS), were investigated. The engineering applicability of the sediment-based LWAs was also assessed. The results showed that it was feasible to use harbor sediments admixed with oyster shells to produce LWAs that were suitable for engineering applications. The LWA properties were highly varied according to the sintering temperature and oyster shell content. Remarkably, the LWAs prepared with a 5–15% oyster shell content and sintered at 1125 °C were suitable for structural lightweight concrete (PD: 1.73–1.83 g/cm3, WA: 12.2–15.1%, CS: 7.2–10.4 MPa). The open porosity was a key factor affecting the particle density, water absorption, and crushing strength of the LWAs. Moreover, the leachability of toxic metals and chloride ions in the LWAs complied with the regulations for building materials in Taiwan. Waste oyster shells could be an excellent additive to lower the optimal sintering temperature required for sediment-based LWA production.