RESISTANCE OF DIFFERENT CEMENT TYPES TO SULFATE ATTACK IN THE LIGHT OF LONG-TERM INVESTIGATIONS

摘要

In the paper long-term determinations of cement mortars immersed for 7 years in Na_2SO_4 solution are presented. The investigation programme concerned many kinds of cements to EN 197-1:2000 Standard specifications and revealed different resistance to sulfate attack. PC and cements containing granulated blastfurnace slag, siliceous fly ash, silica fume and limestone constituents were tested. The sulfate corrosion process of the cement mortars was estimated by expansion determinations and corrosion products investigation. The results confirmed distinctly advantageous effect of mineral additions on the sulfate resistance improvement of cement mortars. Especially very good sulfate resistance was shown for cements CEM Ⅲ and CEM Ⅳ/B containing very high additions of granulated blastfurnace slag and fly ash constituents. It was found out that the long-term sulfate corrosion destruction of cement mortars is stimulated mostly by crystallization of gypsum in the cement matrix.