Heat curing and delayed ettringite formation

This paper reports some preliminary results from a study of the effect of elevated temperature curing on mortars and the phenomenon of delayed ettringite formation (DEF). Mortars made from cements with sulphate levels of 3%, 4%, and 5% and with 5% sulphate and added alkali were cured at 20 and 90°C and subsequently stored in water. Expansion measurements showed a pessimum effect with increasing SO3 content. Mortars which expanded showed a corresponding decrease in strength. X-ray diffraction (XRD) studies indicated that no ettringite is present after heat treatment but re-forms over time within the material. However, the ultimate levels of ettringite reached do not correspond to the magnitude of expansion observed. X-ray microanalysis shows that immediately after the heat treatment the aluminate species and most of the sulphate species are incorporated within the C-S-H gel. The concentrations of these species decrease during expansion, such that at the end of expansion the amounts remaining correspond to the presence of AFm phase mixed with C-S-H.

Published in:
Materials Research Society Symposium - Proceedings, 370, null, 67-76
Cited By (since 1996): 16
Export Date: 1 June 2011
Source: Scopus
Other identifiers:
Scopus: 2-s2.0-0029225624

 Record created 2011-06-06, last modified 2018-03-17

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