Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc

Jin, F. and Al-Tabbaa, A. (2014) Evaluation of novel reactive MgO activated slag binder for the immobilisation of lead and zinc. Chemosphere, 117, pp. 285-294. (doi:10.1016/j.chemosphere.2014.07.027)

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Abstract

Although Portland cement is the most widely used binder in the stabilisation/solidification (S/S) processes, slag-based binders have gained significant attention recently due to their economic and environmental merits. In the present study, a novel binder, reactive MgO activated slag, is compared with hydrated lime activated slag in the immobilisation of lead and zinc. A series of lead or zinc-doped pastes and mortars were prepared with metal to binder ratio from 0.25% to 1%. The hydration products and microstructure were studied by X-ray diffraction, thermogravimetric analysis and scanning electron microscopy. The major hydration products were calcium silicate hydrate and hydrotalcite-like phases. The unconfined compressive strength was measured up to 160 d. Findings show that lead had a slight influence on the strength of MgO-slag paste while zinc reduced the strength significantly as its concentration increased. Leachate results using the TCLP tests revealed that the immobilisation degree was dependent on the pH and reactive MgO activated slag showed an increased pH buffering capacity, and thus improved the immobilisation efficiency compared to lime activated slag. It was proposed that zinc was mainly immobilised within the structure of the hydrotalcite-like phases or in the form of calcium zincate, while lead was primarily precipitated as the hydroxide. It is concluded, therefore, that reactive MgO activated slag can serve as clinker-free alternative binder in the S/S process.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Jin, Dr Fei
Authors: Jin, F., and Al-Tabbaa, A.
College/School:College of Science and Engineering > School of Engineering > Infrastructure and Environment
Journal Name:Chemosphere
Publisher:Elsevier
ISSN:0045-6535
ISSN (Online):1879-1298
Published Online:12 August 2014

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