Potential errors in the quantitative determination of hydrated calcium sulphates in cement by differential scanning calorimetry - Dunn, J.G.; Oliver, K.; Sills, I. (Elsevier)
Gypsum and hemihydrate can be quantitatively determined in cement samples by DSC. However, difficulties have been found with this method, related to the properties of the cement sample and the use of synthetic cement standards to produce the calibration curve.In the present work, a number of cement samples were found to give a very distorted endothermic peak associated with the first dehydration step, in which gypsum is converted to hemihydrate. The determined gypsum values were lower than expected. The low results were found to occur when the clinker used was more reactive than is usual for cement clinkers. An explanation for this behaviour is proposed, and information is given to allow assessment of the reliability of results obtained. Ways of minimizing errors are also suggested.The effect of humidity on stored samples and standards was investigated, and recommendations for storage conditions are made.Synthetic standard cements were prepared by mixing clinker with either (a) gypsum and hemihydrate, or (b) gypsum that had been partially dehydrated to a mixture of gypsum and hemihydrate. The former method is recommended.
http://linkinghub.elsevier.com/retrieve/pii/0040-6031(89)85425-5
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