Measuring Chromium in General Purpose (GP) Cement

Author: J. Mohammadi, W. South  
Type: Journal Paper
Date: 2016/08/26
Publisher: ASTM International
Source:  Journal of Testing and Evaluation. 2016 Aug 26; 45(4)
ISSN: 0090-3973  

Keywords: hexavalent chromium, cement, repeatability, reproducibility, proficiency test      

This paper presented the results of a cement proficiency test undertaken to measure the water soluble chromium content of cement. The water-soluble chromium (Cr6+) content of cement samples from major cement producers in Australia were determined by industrial laboratories in Australia and Europe based on the methods given in Australian Standard AS 2350.15 and the European Standard EN 196.10, respectively. The accuracy of the Australian test method and the precision of the Australian laboratories were investigated by performing proficiency tests. Applying the ASTM E691-15 calculation procedure, the level of systematic error associated with the Australian test method and the relevant suggestions for improvement were provided. The results showed the repeatability and reproducibility for the AS 2350.15 test method were 8 and 18 %, respectively, and comparable to the European results. It was found that the inductively coupled plasma (ICP) tests for the total and water soluble chromium content of cement could be considered an acceptable alternate measurement method. An investigation into the ratio of total chromium Cr to Cr6+ was explored to see if it might be used as an indicator of water-soluble content. Although a very weak correlation was observed between Cr6+ and Cr, in no cases does the ratio of Cr6+/Cr exceed 22 %.