Physical-chemical, mechanical and microstructural properties of contaminated marine sediments solidified by high volume of incinerated sewage sludge ash Yi-fan Zhou, Jiang-shan Li, Chi Sun Poon* Department of Civil and... [ view full abstract ]
Physical-chemical, mechanical and microstructural properties of contaminated marine sediments solidified by high volume of incinerated sewage sludge ash
Yi-fan Zhou, Jiang-shan Li, Chi Sun Poon*
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University,
Hung Hom, Kowloon, Hong Kong
Correspondence author: cecspoon@polyu.edu.hk
WASCON 2018 ABSTRACT
As the disposal of incinerated sewage sludge ash (ISSA) and dredged marine sediments is a great challenge for the limited landfill space in Hong Kong, the present research investigates the use of high volume (20% wt. of sediment) ISSA in combination with cement/lime to solidify/stabilise (S/S) contaminated marine sediments, providing a novel way to reuse them as filling materials in the road sections. The porous nature of ISSA contributes to its excellent water absorption abilities, improving the solidification process of the marine sediment which typically has a very high moisture content (~80%). The impacts of binder amount (5% and 10% wt. of sediment) and curing time (7, 28 and 90 d) on the change of performance of the treated sediment, including natural dewatering, workability, pH, Atterberg limits, hydraulic permeability, unconfined compressive strength and leachability of heavy metals were studied. A series of microstructural laboratory tests such as mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed to evaluate the mechanisms controlling strength development and heavy metals immobilisation. The results showed that the S/S treatment improved the engineering properties of the sediment, but at the cost of decreased workability, especially for the lime-treated samples. Lime can be used as a replacement cement for its better performance on heavy metals immobilisation and carbon emission reductions. Additionally, the hardened sediment samples solidified with 10% of lime and ISSA could attain a strength of 1.6 MPa after 28-d curing. The SEM and XRD tests verified the formation of hydrated cementitious compounds CSH/CASH/calcite, highlighting the chemical transformation of the binders in the sediments. Therefore, this study provides a new approach of reusing ISSA for the treatment of marine sediments and using the product as a value-added construction material.
Key Words: contaminated marine sediments; incinerated sewage sludge ash; solidification/stabilization; heavy metals
New products, applications and machinery , Development of testing methods and standardization
