Sustainable Use of Dredge Materials at Engineering Fills and the Investigation of Their Performance with Different Additives

In the world, millions of cubicmeters of materials are dredged from sea or channel bottoms each year. It is both uneconomical and dangerous for the environment, when dredged materials are considered as waste and stored at the landfills or discharged at the offshore areas. For that reason, studies on the sustainable usage of dredged materials, which has high water content or organic matter, increase especially at fills, structural materials and topsoils. Generally one or two different chemical additives (lime or cement) were used with different proportions and water contents. In this study, a dredged soil from Ä°zmir Bay was selected and the optimum combination was determined for compaction characteristics and durability. The standard Proctor test results have shown that, in the presence of 7% lime and cement the maximum dry unit weight of the samples were 1.75 and 1.65 g/cm3, respectively. However, when 3.5% lime and 3.5% cement were mixed and used together, the maximum dry unit weight became 1.72 g/cm3. In the second part of the study, the strength properties of the modified dredge material with lime and fly ash were determined in the presence of distilled water and natural seawater for their potential usage in onshore fills. Optimum lime and fly ash contents in terms of strength were determined for the Izmir Bay dredged soil by unconfined compression tests. The test results also revealed that dredged soil specimens treated with sea water had systematically greater unconfined compressive strengths than that of their distilled water counterparts.