Unsaturated behaviour of a stabilized marine sediment: A comparison of cement and GGBS binders

In order to ascertain the contaminant-encapsulation potential of stabilized soil, an understanding of its unsaturated hydraulic behaviour, specifically the Soil Water Retention Curve (SWRC), is paramount. In this paper, centrifuge testing was used to obtain SWRCs for sediment dredged from an Irish harbour, stabilized with Ordinary Portland cement (OPC) and Ground Granulated Blast Furnace Slag (GGBS) binders. The effects of the different binder proportions and different curing times on both the Unconfined Compressive Strength (UCS) and SWRC were investigated, with the support of Scanning Electron Microscope (SEM) data. The Fredlund and Xing (1994) empirical model was found to provide the best fit to the stabilized sediment SWRCs. The water holding capacity was found to increase with increased binder content, increased GGBS proportion in the binder and increased curing time, suggesting that high-GGBS binders are most suitable for locking in contaminants. An examination of relationships between one of the model parameters (Air Entry Value, AEV) and UCS further highlights differences in strength and water retention mechanisms between the two binder combinations. In addition to its well-known environmental credentials, this research highlights the technical merits in using GGBS in contaminated sediment reuse projects.