Study of reducing of Cr (VI) using different reducing agents in cemenitious systems

The EU Directive, 2003/53/EC is to restrict the marketing and use of cement andcement-based preparations, where they contain when hydrated, more than 0.0002 % (2ppm) chromium (VI) of the dry weight of cement. This legislation is designed to minimisethe risk of chromate related allergic dermatitis that can arise from use of cement. In mostcement producers, the soluble chromium (VI) levels will be controlled by reducing agentsadded to the cement at the grinding stage.In this study, five different reducing agents are used to reduce below 2 ppm ofCr(VI) amounts in cement and whether reducing agents could be reduced or not isinvestigated to below 2 ppm of Cr(VI) in cement. Furthermore, reducing agents are testedfor shelf life capacity in cement. This reducing agents are FeSO4.7H2O, Na2S2O4, Na2S2O5,Na2S2O3.5H2O and CaSx. Two different cement samples which have 52 ppm and 12 ppmcontaing hegzavalent chromium are used for experiments.As result; FeSO4.7H2O, Na2S2O4 and CaSx are observed of reducing Cr(VI) tobelow 2 ppm. Na2S2O5 and Na2S2O3.5H2O are not effective to remove the Cr(VI).FeSO4.7H2O is more effective for shelf life tests from Na2S2O4 and CaSx.Key Words: Cement, chromium (VI), reduction