Influence of Fly Ash–Based Geopolymer Binder on the Sedimentation Behavior of Dredged Mud

Abstract

This laboratory study investigated the sedimentation behavior of a fly ash–based geopolymer-stabilized dredged-mud slurry extracted from the Port of Townsville, Queensland, Australia. Settling-column tests were conducted to study the sedimentation behavior of 400%-water-content dredged mud of untreated and geopolymer-stabilized slurries at 6, 12, and 18% content by weight. Dredged-mud slurry interface height movements with elapsed time were recorded, and their settling patterns were observed. Mineralogical and microstructural characteristics of dried, untreated, and geopolymer-stabilized dredged-mud sediments were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) analysis. The study found that a fly ash–based geopolymer gel coating the dredged-mud particles in the slurry led to a flocculated settling behavior, and the geopolymer stabilization reduced the overall dredged-mud slurry sedimentation duration. XRD and SEM/EDS analysis showed that the geopolymer stabilization altered the microstructure of stabilized dredged-mud sediment and reduced its desiccation shrinkage cracks.