Microscopic investigations of the effect of ultrafine particles on cement paste properties

The utilization of fine and ultrafine particles for concrete manufacturing has received considerable attention in recent years. Interest has been more and more addressed towards the utilization of fine and ultrafine particulates products of natural origin and/or resulting from waste and industrial by-products, in order to reduce cement consumption, also reducing the environmental impact linked to its production. In this paper materials coming from two natural pozzolanic deposits in Italy have been utilized. Pozzolanic materials have been milled below 25 ?m and the resulting products utilized, in different recipes, for the preparation of different blended cements. It was found as the addition of pozzolanic fine fractions: i) does not increase cement compressive strength, ii) flowability characteristics of slumps result higher than the reference mortar sample and, finally, iii) blended mortars compressive strength is comparable with that of pozzolanic blended cement