Solidification/stabilization treatment of Hong Kong marine deposits slurry at high water content by ISSA and GGBS

Abstract

Soft soils have been adopted as a conventional fill material in land reclamation projects, which is quite promising in Hong Kong with a huge mass of dredged marine sediments produced per year. It is proposed to use Hong Kong marine deposits (HKMD) as fill material treated by stabilisation/solidification (S/S) technology with sustainable binding material. In this work, lime, incinerated sewage sludge ash (ISSA) and ground granulated blast furnace slag (GGBS) were selected as the binding materials. The S/S performance of the binders on HKMD slurry was investigated. The results showed that the use of ISSA and GGBS as part of the binder is effective in promoting the strength of HKMD slurry with a high initial water content of 200%. The HKMD slurry treated by 30% binders (30% lime and 70% (ISSA + GGBS) with ISSA: GGBS = 3) gains strength, which became higher with increasing curing time. The results from X-ray diffraction (XRD), thermo-gravimetric (TG) analysis and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) presented the formations of calcium (aluminium) silicate hydrate (C-(A)-S-H), Friedel’s salt, and ettringite, which are mainly responsible for the strength increase of treated HKMD with their phases filling into the pores, interlocking and reinforcing the particles in the mixture. The porosity of the treated HKMD in bulk and powder state was determined by mercury intrusion porosimetry technique (MIP) and nitrogen adsorption/desorption isotherms (NAI), it is found that the bulk porosity of treated HKMD samples reduces with curing time due to the neoformations, especially the ettringite crystal by SEM results. This work indicates the potential application of lime-activated recycling wastes (i.e., ISSA and GGBS) for S/S treatment of HKMD slurry.