Effect of curing temperature and cement chemistry on the potential for concrete expansion due to DEF

Five cements with different chemistries were used to produce concretes that were cured in a controlled fashion at 23, 60, 65, 70, 80, and 90degreesC (73, 140, 149, 158, 176, and 194degreesF). Expansions due to delayed ettringite formation (DEF) were correlated with a rapid DEF predictive technique. The rapid DEF predictive technique is based on a comparison of the quantity of ettringite measured using differential thermal analysis (DTA) at 24 hours of curing to that measured after the forced hydration of the powdered sample. The lengths of companion concrete prisms have been measured through 3(1)/(2) years. The expansion behavior of the concrete with respect to curing temperature and cement chemistry is presented, as well as a comparison to the DTA predictions. Expansion is occurring in five out of six concretes cured to 90degreesC (194degreesF). One concrete cured to 65degreesC (149degreesF) is currently expanding, but no concrete cured below 65degreesC (149degreesF) is expanding. Suggestions are made as to threshold values of Delta Ettringite that correlate with the current expansion behavior. Since the onset of expansion in some cases has not occurred until after two years, these correlations need to be revisited in the future. Recommendations for curing temperature limits when concrete will be exposed to wet service conditions are made.