Title:
Rheology and Early-Age Reactivity of Calcined Kaolinite
Author(s):
Yannick Demeusy, Sandrine Gauffinet and Christophe Labbez
Publication:
Symposium Paper
Volume:
362
Issue:
Appears on pages(s):
610-614
Keywords:
calcined clay, rheology, early age reactivity, calorimetry, conductimetry
DOI:
10.14359/51741015
Date:
6/14/2024
Abstract:
Calcined clay cements are a promising route to reduce the carbon footprint of cement production. One of the obstacles to their development is their high water demand at low clinker factors. Here, a model system of portlandite, gypsum, and calcined clay is used to simulate the rheology and early age reactivity of calcined clay cement. Eight different kaolinitic clay rocks containing a large range of kaolinite content and additional phases are studied. The reactivity is studied in diluted and concentrated conditions by conductimetry and isothermal calorimetry. The rheology by dynamic rheometry. The stiffening of the paste is found to increase rapidly with the hydration rate of the calcined kaolinite to form ettringite. The rheology of the model system is observed to be controlled by hydration in less than 5 minutes for the more reactive calcined kaolinite rock and not more than 30 minutes for the less reactive. The early reactivity of calcined clay rocks is found to be uncorrelated with the kaolinite content and independent of the calcined clay rock/water ratio. In contrast, results indicate that the crystallinity of the kaolinite and, to a lesser extent, the iron content of the clay rock are crucial parameters.