The usability of calcined clay blended cements for special durability problems of concrete

In this article results of several investigations helping to assess the effect of different calcined clay blended cements on extremely stressed concretes are shown.
Two ordinary Portland cements mainly differing in their alkali content and three different clays containing as mineral bases kaolinite, montmorillonite and illite have been selected for the experiments.
Microstructure of hardened pastes of the pure and blended Portland cements has been investigated. Compressive strength, sulphate resistance and alkali-silica reaction resistance of mortars based on these cements have been determined.
Calcined clays, regardless of the clay mineral base, are useful pozzolans, which give a moderate to good strength contribution to the cement. With regard to the concrete durability, certain restrictions for calcined montmorillonitic and illitic clays have to be imposed depending on the exposure. As a consequence, these materials are not able to achieve performances comparable to metakaolin and, therefore, can only be limitedly used in concrete application with higher demands for durability.

Author: A. Truemer, H.-M. Ludwig

Section: Science and production

Keywords: calcined clay blended cements, metakaolin, pozzolana, concrete durability, sulphate resistance, alkali-silica reaction resistance