Portlandite consumption in metakaolin cement pastes and mortars

Cement mortars and pastes containing 0, 5, 10 and 15% replacement of cement with metakaolin and with a waterbinder (wb) ratio of 0.55 have been moist cured for periods from 3 to 365 days. The Portlandite content at different ages has been determined by thermogravimetric analysis and this has been related to changes in relative strength. Ca(OH)2 in mortars was found to be less than that in pastes. In the metakaolin mortars and pastes removal of Portlandite by pozzolanic reaction reached a maximum at about 14 days, corresponding with a maximum in relative strength. Beyond 14 days severe retardation of the pozzolanic reaction was observed and relative strength rapidly declined.

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