Influence of the microsilica state on pozzolanic reaction rate

Silica fume is generally supplied as an ultrafine powder in its original sl ate, densified or in suspension. The difference in slates should not influe nce the pozzolanic behaviour of this by-product in a cementitious matrix. I n the present work, experimental results relating to pozzolanic reaction ha ve been obtained by different methods: a chemical method, in which lime fix ed by pozzolanic material through time is quantified, and a physicochemical method based on the Langavant calorimeter. By the second method, informati on regarding silica fume is obtained from the value of heat of hydration re leased by a mortar containing this by-product. These results show that the silica fume in its densified state considerably decreases its chemical reac tivity with calcium hydroxide (pozzolanic activity). (C) 1999 Elsevier Scie nce Ltd. All rights reserved.