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Description: Extensive review and analysis of the causes, effects, and prevention of secondary (delayed) ettringite (expansive sulfate compounds) in concrete. Case studies of damage in concrete are examined, along with test methods, and critical factors to consider to avoid potential damage. Eight chapters plus a subject index. This report is also found on DVD021.
The report comprises a review and analysis of the available literature pertaining to the causes, effects and prevention of delayed ettringite in concrete. Over 300 publications have been examined. Case studies of damage in concrete possibly caused by delayed ettringite formation are examined first. Fundamental research on ettringite formation, its chemistry, and deposition mechanisms is then reviewed. Key investigations on the topic are analyzed in detail. Next, the potential importance of (a) method of heat-curing and (b) the chemistry of cement is outlined. In the final chapter, a rapid test for evaluation of potential delayed ettringite susceptibility (the "Duggan" test) is evaluated. The analysis indicates that there appears to be a potential for a delayed ettringite formation problem in North America; it is highly probable that delayed ettringite formation can lead to significant deterioration of heat-treated concrete. However, it is unlikely that delayed ettringite formation is, or will be, the sole mechanism responsible for premature deterioration. The critical factors that determine extent of damage due to delayed ettringite formation are (a) duration of delay period before heating the concrete; (b) severity of the heating and/or cooling regime; and (c) the SO3/A12O3 ratio of the cement. There is no evidence that non heat-treated concrete is susceptible to this phenomenon.
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