Portland pozzolana cement in India with respect to total chromium and hexavalent chromium content

The objective of the present research work was to evaluate total chromium and hexavalent chromium [Cr(VI)] in Portland cement in India especially for fly ash-based Portland pozzolana cement. Various additives have been used for the effective reduction of Cr(VI) in wet cement. All cement samples from various regions were collected to determine the total chromium and Cr(VI). Total chromium was analysed on an inductively coupled plasma optical emission spectrometer, whereas Cr(VI) was analysed using the 1,5-diphenyl carbazide method on a UV-visible spectrophotometer. A group of additives was studied to evaluate their effectiveness for Cr(VI) reduction in the cement samples. The additives were incorporated and mixed in cement for experimentation purposes using a disc mill. The difference in Cr(VI) before and after addition for the particular additive was checked using a spectrophotometer by the 1,5-diphenyl carbazide method at 540 nm. The reduction in Cr(VI) due to use of additives was reconfirmed at two wavelengths, 372 and 274 nm, respectively. Sodium borohydride (NaBH₄) and stannous sulfate (SnSO₄) were found to be the best additives for reducing Cr(VI) in cement among the additives under investigation in this study.