Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/74637
Title: Influence of lead on stabilization/solidification by ordinary Portland cement and magnesium phosphate cement
Authors: Wang, YS 
Dai, JG 
Wang, L 
Tsang, DCW 
Poon, CS 
Keywords: Leachability
Lead-contaminated soil
Magnesium phosphate cement
Phosphate precipitation
Stabilization/solidification
Issue Date: 2018
Publisher: Pergamon Press
Source: Chemosphere, 2018, v. 190, p. 90-96 How to cite?
Journal: Chemosphere 
Abstract: Inorganic binder-based stabilization/solidification (S/S) of Pb-contaminated soil is a commonly used remediation approach. This paper investigates the influences of soluble Pb species on the hydration process of two types of inorganic binders: ordinary Portland cement (OPC) and magnesium potassium phosphate cement (MKPC). The environmental leachability, compressive strength, and setting time of the cement products are assessed as the primary performance indicators. The mechanisms of Pb involved in the hydration process are analyzed through X-ray diffraction (XRD), hydration heat evolution, and thermogravimetric analyses. Results show that the presence of Pb imposes adverse impact on the compressive strength (decreased by 30.4%) and the final setting time (prolonged by 334.7%) of OPC, but it exerts much less influence on those of MKPC. The reduced strength and delayed setting are attributed to the retarded hydration reaction rate of OPC during the induction period. These results suggest that the OPC-based S/S of soluble Pb mainly depends on physical encapsulation by calcium-silicate-hydrate (C–S–H) gels. In contrast, in case of MKPC-based S/S process, chemical stabilization with residual phosphate (pyromorphite and lead phosphate precipitation) and physical fixation of cementitious struvite-K are the major mechanisms. Therefore, MKPC is a more efficient and chemically stable inorganic binder for the Pb S/S process.
URI: http://hdl.handle.net/10397/74637
ISSN: 0045-6535
EISSN: 1879-1298
DOI: 10.1016/j.chemosphere.2017.09.114
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