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Ripening reduces the shrinkage of processed dredged material

Oing, Katja, Gröngröft, Alexander, Eschenbach, Annette
Journal of soils and sediments 2020 v.20 no.1 pp. 571-583
air drying, construction materials, cracking, dewatering, dredged materials, extensibility, marshes, mechanical properties, shrinkage
PURPOSE: The utilization of dredged material in dike construction as a substitute for traditionally used materials is considered as an option to preserve natural resources such as marsh sediments. As a prerequisite for this application, the equivalency with respect to soil physical and mechanical properties of the materials must be assessed. Previous investigations have shown pronounced differences in shrinkage behavior and desiccation cracking between sediments and dredged material. The key objective of the study was to assess whether shrinkage of processed dredged material can be reduced by further processing, i.e., dewatering, which can be referred to as ripening. MATERIALS AND METHODS: To compare the shrinkage behavior of the materials, three different methods of different scales were applied. Small-scale methods conducted were the standard procedure for the determination of the shrinkage limit and the determination of the coefficient of linear extensibility (COLEᵣₒd). Large-scale shrink-swell experiments were carried out in a specially constructed test system with 90 l capacity for a period of up to 385 days. Here the materials were ripened, i.e., air-dried, until shrinkage almost ceased, and a rewetting-air-drying cycle was conducted. Shrinkage and swelling were determined during the processes by measuring the changes in volume. On the ripened materials, COLEᵣₒd was determined. RESULTS AND DISCUSSION: The experiments show that the shrinkage behavior of processed dredged material can be ameliorated by ripening. COLEᵣₒd of the ripened materials were about 20–80% lower than COLEᵣₒd of the un-ripened materials. The large-scale shrink-swell experiments showed that shrinkage in the second drying cycle amounted to less volume than in the first drying cycle and that shrinkage behavior in contrast to the first drying cycle, where pronounced proportional shrinkage was observed, was dominated by structural and residual shrinkage in this cycle. CONCLUSIONS: Ripening of processed dredged material is considered a useful pre-treatment option to ameliorate the shrink-swell behavior of processed dredged material and to obtain a better functional equivalency with traditionally used dike construction materials such as fine-grained marsh sediments.