Hexavalent chromium analysis, reduction and stabilization in cement and concrete
Date
2008-03-11T12:25:20Z
Authors
Lokothwayo, Robson Bhekisisa
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Abstract
Abstract
Hexavalent chromium is one of the toxic contaminants unavoidably widespread in the
environment that exists in cement and concrete. Cement producers need to determine and
control the content of hexavalent chromium, hence this study investigated the effect of
environmental parameters on the leachability, stability and reduction of Cr(VI) in
different types of concrete. Concrete cubes were made with different cement mixtures,
and in some cases, reducing agents were added. The bulk and designed surface leaching
experiments that simulated different environmental conditions were devised for leaching
of Cr(VI). The Cr(VI) content in cement and concrete leachate solution was determined
using optimized Adsorptive Stripping Voltammetry method which proved to be very
sensitive and selective. Parameters like addition of MnO2, aging of concrete, increase of
temperature, UV variation and decrease in pH enhanced the leachability of Cr(VI).
Cement type also affected the Cr(VI) stabilization. Attempts to stabilize Cr(VI) included
addition of humic acid which proved to be not effective while the addition of ferrous
sulfate was successful in reducing and stabilizing Cr(VI) in concrete.