ANALYSIS OF DIFFERENT CEMENT BASED PASTES IN S02 AND N02 ATMOSPHERES

The paper explains the behaviour of cements of different composition in atmospheres rich in sulphur-dioxide and nitrogen-dioxide. As a result of 180 day long exposition to sulphur-dioxide rich atmosphere the minimal increase of the sulphate ion compound (4%) occurred in cements containing 20% fly ash, while the maximum increase (7%) was found in cements with 40% slag content. The results for portland cements were between these two extreme values. While on the surface of portland cement samples a well-adhesive salt layer appeared, the outer 0.8-1.0 mm of samples with 40% slag peeled off by the end of the ISO day long treatment period. The main constituent of both the salt and the peeled off layer was gypsum, formed from the portlandite and the carbonate phase of the samples. The nitrate content in ISO day old samples stored in nitrogen-dioxide rich atmosphere turned out to be between 1.1-1.4% unaffected by the composition of the cement.