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DOI: http://dx.doi.org/10.1065/jss2003.04.077

GOAL. Annually, 400.000 m3 harbour sediments are dredged to maintain the water depth in the harbours of Bremen and Bremerhaven. The sediment contains organic and inorganic pollutants and hence is deposited on a landfill. Because of the limited capacity of that landfill alternative treatment techniques are investigated. This study aims to evaluate the production of Light Weight Aggregates (LWA) from harbour sediments with respect to the product quality and environmental aspects of the use of the LWA.

METHODS. LWA were produced at pilot scale using harbour sediment as a component of the raw material. The physical characteristics of the LWA were classified according to German constructional standards,. the leaching behaviour was described applying German standard leaching tests and pH-static experiments. In the leaching tests pH-value and grain size were varied to simulate potential changes in the course of the LWAs life-cycle. Besides comparing the mobilised concentrations of heavy metals with threshold values and reference material the mobilisation of arsenic for a given disposal scenario calculated.

RESULTS. The harbour sediments are suitable for LWA production due to its perpetual availability, homogeneity and mineralogical and chemical composition. Leaching data reveal that organic matter originating from harbour sediments was not totally destroyed during the production of LWA. Data analyses showed, that arsenic was stabilised and heavy metals were immobilised within the LWA.

CONCLUSION AND RECOMMENDATION. We conclude LWA are not hazardous to soil or groundwater during their whole life cycle: Neither during the use of LWA, e.g. in construction, nor afterwards, when they are disposed as mineral demolition mass. A LWA-production using harbour sediments as raw material should be scaled up to a demonstration scale in order to verify the results for a larger throughput and to calculate precise operational costs of the production.