Silicate anions polymerization in the pastes of OPC and of OPC-silica fume blends during hydration and after action of leaching attack-part II: Study by use of molybdate method

Abstract

Pastes made from OPC and OPC-silica fume blends, previously investigated by use of the direct TMS method, were studied by using the molybdate method in order to determine changes in polymerization of Si-anions due to hydration and pozzolanic reaction and due to attack of leaching. The results confirm that by the progress of hydration, from 50 to 250 days, the share of silicates which cannot be hydrolytically decomposed and complexed through molybdate reaction decreases, thus contributing to the increase of the oligomeric-polymeric fraction of Si-anions. The leaching attack on the cement pastes brought about polymerization of Si-anions in those mixes. The changes of Si-anion polymerization characteristics ( Δ S 180-values) and the changes of the pH-values show that silica fume containing cement pastes better resist such kind of aggression.