A method for the determination of total Cr(VI) in cement

Portland cement is often used to solidify wastes in order to prevent heavy metals from eluting, despite the fact that most cements contain traces of soluble Cr(VI). It was found that the leachability of Cr(VI) for the soil stabilized by cement was high in some cases, and the amount of Cr(VI) leached was larger than could be accounted for by the '' Soluble Cr(VI)'' in the cement as determined by the standard method. Since the existing analytical standards only deal with '' soluble Cr(VI)'' in cement, we had to develop a new procedure to measure the total Cr(VI) in cement, making use of a complete dissolution in acid. Application of this method to several different ordinary Portland cements showed that 50-80% of their total Cr is typically extracted as Cr(VI). We also observed that the interstitial (calcium aluminate/ferrite) phase in Portland cement clinker usually contains higher concentrations of both Cr and Cr(VI) than the calcium silicate phases. (c) 2005 Elsevier Ltd. All rights reserved.