The effect that the pozzolanic reaction of metakaolin has on the heat evolution in metakaolin-cement mortars

The hydration heat of mortars or concretes may be decreased by means of pozzolanic additions. Materials that exhibit pozzolanic activity can decrease the hydration heat by means of cement substitution, which increases the heat generated in hydration due to the pozzolanic reaction. Thus, the evolution of the hydration heat with time represents a reference point when establishing the pozzolanic activity of materials; by monitoring this heat, the behaviour of mortars or concretes during hydration can be established. Tn this work, the influence of the pozzolanic activity of the metakaolin (MK) on the hydration heat has been studied in comparison to the behaviour of other traditional pozzolanic materials such fly ash and silica fume. The results revealed that MK mortars produce a slight heating increase when compared to a 100% Portland cement mortar, due to the high pozzolanic activity of MK. With respect to the hydration heat, MK-blended mortar showed closer behaviour to silica fume than to fly ash. (C) 2000 Elsevier Science Ltd. All rights reserved.