The PONKCS method applied for time resolved XRD quantification of supplementary cementitious material reactivity in hydrating mixtures with ordinary Portland cement

A method is presented to determine the reactivity of supplementary cementitious materials (SCMs) in blended cement systems. To this end, hydration of ordinary Portland cement (OPC) and of OPC blended with the SCMs microsilica and metakaolin has been measured by X-ray diffraction (XRD) and heat flow calorimetry. The quantities of the SCMs in the hydrating mixtures, although of very low crystallinity, could be directly determined by Rietveld refinement employing a method for partially or not known crystal structures (PONKCS method). Considerable amounts of microsilica and metakaolin already react during the first day of hydration in addition to an increased reaction of the cement phases due to the filler effect. The phase assemblage in the hydrated samples is influenced by the SCM present. (C) 2019 Elsevier Ltd. All rights reserved.