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The effect of delayed ettringite formation and alkali-silica reaction on concrete microstructure
The results show that the formation of ettringite will augment the expansion of the mortars caused by the alkali-aggregate reaction. This increased expansion is also the consequence of the delayed ettringite formation in steam-cured mortars , and in mortars stored at temperature of 38 deg C. Irrespectively of the conditions of the processing or curing of mortars, the samples prepared from cement with a very small content of SO3 always display the smallest expansion. Further proof of the share of delayed ettringite in the expansion of mortars is the importance of SO3 content. A comparison of mortar I, which contains 2.29 % SO3, with mortar Ia with a 3.76 % content of SO3, points to the considerable role of delayed ettringite formation, for the maximum level of this expansion is connected with a content of approximately 4 % of SO3. A separate matter is the lack of expansion in mortars I and II containing opal, which were subjected to steam curing. This phenomenon cannot be explained on the basis of the tests. We may only note here that the behaviour of the mortars containing reactive aggregate is variously explained in the literature. However, mortars cured at a temperature of 38 deg C behave differently. The scale of the increasing expansion is maintained (mortars II, I and Ia) but the expansion of sample I is considerably greater than for the non-steam cured mortar sample and close to the expansion in sample Ia. In this case, the expansion connected with the opal reaction is predominant, while ettringite has a smaller importance. This is attested by a considerably greater expansion of mortar II, which contains very little SO3. The formation of ettringite - whether delayed or connected with the recrystallisation of this phase - increases the expansion caused by the alkali-silica reaction.
The effect of delayed ettringite formation and alkali-silica reaction on concrete microstructure
The results show that the formation of ettringite will augment the expansion of the mortars caused by the alkali-aggregate reaction. This increased expansion is also the consequence of the delayed ettringite formation in steam-cured mortars , and in mortars stored at temperature of 38 deg C. Irrespectively of the conditions of the processing or curing of mortars, the samples prepared from cement with a very small content of SO3 always display the smallest expansion. Further proof of the share of delayed ettringite in the expansion of mortars is the importance of SO3 content. A comparison of mortar I, which contains 2.29 % SO3, with mortar Ia with a 3.76 % content of SO3, points to the considerable role of delayed ettringite formation, for the maximum level of this expansion is connected with a content of approximately 4 % of SO3. A separate matter is the lack of expansion in mortars I and II containing opal, which were subjected to steam curing. This phenomenon cannot be explained on the basis of the tests. We may only note here that the behaviour of the mortars containing reactive aggregate is variously explained in the literature. However, mortars cured at a temperature of 38 deg C behave differently. The scale of the increasing expansion is maintained (mortars II, I and Ia) but the expansion of sample I is considerably greater than for the non-steam cured mortar sample and close to the expansion in sample Ia. In this case, the expansion connected with the opal reaction is predominant, while ettringite has a smaller importance. This is attested by a considerably greater expansion of mortar II, which contains very little SO3. The formation of ettringite - whether delayed or connected with the recrystallisation of this phase - increases the expansion caused by the alkali-silica reaction.
The effect of delayed ettringite formation and alkali-silica reaction on concrete microstructure
Der Einfluss der verzögerten Ettringitbildung und der Alkali-Silica-Reaktion auf die Mikrostruktur von Beton
Owsiak, Zdzislawa (author)
Ceramics Silikaty, Prag ; 54 ; 277-283
2010
7 Seiten, 9 Bilder, 2 Tabellen, 26 Quellen
Article (Journal)
English
Portlandzement , Beton , Mikrostruktur , Ettringit , Bildungsmechanismus , Alkali-Silica-Reaktion , Natriumoxid , SO3 , Klinker , Mörtel , Opal , Aggregation , Hitzehärten , Dampf , Temperatureinfluss , Volumenvergrößerung , Rasterelektronenmikroskopie , Röntgenbeugung , energiedispersive Röntgenspektrometrie
The effect of delayed ettringite formation and alkali-silica reaction in of concrete microstructure
| British Library Online Contents | 2010