Current literature about calcined clays as future Supplementary Cementitious Material (SCM) is often limited to the role of 1:1 dominated clays as raw material. However, such clays are the exception in Europe: mixtures of various clay minerals represent the predominant material resources – so-called common clays. Through a comparison with 1:1 dominated clays, this article looks specifically at the suitability of illitic, smectitic and common clays as SCM. The reactivity of eleven different clays was assessed via the R3 tests and compressive strength tests on mortar with six different cements. The strength contribution of 2:1 dominated clays proofed relevant. This holds especially for calcined illite at 2 days and for calcined smectite at 28 days. A significant increase in strength was observed with the 1:1 dominated clays only at 28 days. The strength contribution of the calcined clays varied depending on the cement used. A mathematical model correlates the mineralogy and fineness of the clays with the Activity Index of the blended cements, making it possible to predict strength at 2 and 28 days. This is also possible with the R3 test, since the heat release of a calcined clay correlates with the Activity Index of the corresponding blended cement.    «

Current literature about calcined clays as future Supplementary Cementitious Material (SCM) is often limited to the role of 1:1 dominated clays as raw material. However, such clays are the exception in Europe: mixtures of various clay minerals represent the predominant material resources – so-called common clays. Through a comparison with 1:1 dominated clays, this article looks specifically at the suitability of illitic, smectitic and common clays as SCM. The reactivity of eleven different clays...    »