C-S-H Quantification Using XRD: A Comparison of the Rietveld and PONKCS Methods

The mineralogical quantification of cementitious materials can be performed using the Rietveld method, provided that suitable crystallographic data is available. X-ray amorphous phases, such as C-(A-)S-H, restrict the use of the Rietveld method because only very little crystallographic information is available. It is possible to get around this shortcoming using the PONKCS method (acronym for Partial Or No Known Crystal Structure) or employing the crystallographic data theorized by Richardson for C-S-H. This study examines the practical application of these two approaches to quantify the C-S-H phase of mature cement paste and the hydration monitoring of CEM I and C3S pastes. The quantifications obtained were compared to the TGA and hydration modeling results. It was shown that the two methods yield comparable and interchangeable results, each achieving an accuracy within 5% of the expected values.