Secondary Ettringite Formation - Proactive Avoidance

By examining the external and internal causes of SEF, the practicing engineer has several options to prohibit SEF from occurring in future concrete projects. Preventive options can be divided into choice of cement, choice of aggregate and curing regime after casting.

If at all possible, the practicing engineer should choose a low or moderate hydrating cement. Cements with low C3A content (below 9-11%) and low SO3 content (below 4%) are optimal in avoiding SEF. Cements with high fineness properties and high alkali contents should be avoided if possible. Choosing cement with a SO3/Al2O3 ratio lower than 0.5 or 0.6 will be successful in prohibiting SEF.

Aggregate choice may influence SEF occurrence. Since SEF often accompanies SEF, reactive aggregates should be avoided in concrete. Strained quartz, chert, and volcanic glass are examples of reactive aggregates that are susceptible to ASR and SEF.

Curing regime is a factor in the occurrence of SEF. If possible, the engineer should keep curing temperatures at 70°C or lower to avoid SEF. Caution must be used in following this guideline, for several researchers have reported SEF occurring in concrete cured under normal conditions.

All suggested preventive measures are not foolproof. Due to the recent history of SEF, much of the phenomenon is not understood, and many researchers have different beliefs about mechanisms, causes, and preventive measures.