Geoenvironmental Evaluation of RCA-Stabilized Dredged Marine Sediments as Embankment Material

Millions of cubic meters of marine sediment are dredged from Chesapeake Bay waters in Maryland each year. Due to their low-strength characteristics, the sediments often need to be amended with other geomaterials for potential use in earthworks projects. However, the environmental effects of the blend need to be thoroughly investigated prior to such use. In an effort to alleviate storage challenges for these dredged sediments, the current study investigates their potential use in highway embankments upon amending them with recycled concrete aggregate (RCA). The laboratory compaction test data indicate that RCA amendment causes an increase in gravel content, decreases the liquid limit, and increases the unit weight of the virgin sediments, resulting in a typical material for embankment construction and satisfying the minimum unit weight requirements set by the local highway authority. pHstat tests and sequential column leaching tests were carried out to evaluate variations in leachate concentrations across pH and time. The RCA addition causes a slight increase in leached metal concentrations; however, all metals except copper remain below water quality limits. The numerical simulations showed that, while contaminant concentrations in leachate from the sequential column leaching tests at times exceed the water quality limits, those concentrations are dissipated and diluted rapidly in situ both in surface waters and in groundwater, and thus are not likely to be of concern.