Development of a Novel Binder Using Lime and Incinerated Sewage Sludge Ash to Stabilize and Solidify Contaminated Marine Sediments with High Water Content as a Fill Material

In this study, incinerated sewage sludge ash (ISSA) was applied to replace ordinary portland cement (OPC) and quick (unhydrated) lime at different ratios of 0%, 20%, and 50% for improving the properties of marine sediments with high water content by solidification/stabilization (S/S) method. Then, the effects of different binders and curing time (7 and 28 days) on sediment properties, including unconfined compressive strength (UCS), shear strength, durability, and leachability of metals were investigated. Test results indicated that lime-ISSA binder had several advantages over OPC-ISSA binder owing to its lower cost, lower environmental footprints, and better strength gains. The UCS, deformation resistance, and shear strength of the specimens prepared using lime as the binder were improved with the increasing addition of ISSA, and the water permeability was also effectively reduced. The results of environmental impact assessment (in particular leaching characteristics) indicated that the leachability of heavy metals in the lime-ISSA stabilized sediments was effectively mitigated. The proposed fill material complied with the acceptance criteria for engineering fills applications. A series of spectroscopic/microscopic laboratory tests including mercury intrusion porosimetry (MIP), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were performed to investigate the mechanisms controlling strength development and metals immobilization. The chemical reactions between the sediments, ISSA, and lime resulted in the formation of hydrated cementitious compounds that facilitated the decrease in pore volume and increase in strength and stabilization of heavy metals. On the whole, the lime-ISSA system could replace the OPC-ISSA binder to particularly improve the geotechnical and environmental properties of the contaminated sediments.