Influence of the microsilica state on pozzolanic reaction rate

Abstract

[EN]Silica fume is generally supplied as an ultrafine powder in its original state, densified or in suspension. The difference in states should not influence the pozzolanic behaviour of this by-product in a cementitious matrix. In the present work, experimental results relating to pozzolanic reaction have been obtained by different methods: a chemical method, in which lime fixed by pozzolanic material through time is quantified, and a physicochemical method based on the Langavant calorimeter. By the second method, information regarding silica fume is obtained from the value of heat of hydration released by a mortar containing this by-product. These results show that the silica fume in its densified state considerably decreases its chemical reactivity with calcium hydroxide (pozzolanic activity).