Secondary Ettringite Formation - Internal and External causes
Although there is debate among researchers concerning SEF, there are several factors that are generally agreed to be responsible for the occurrence of SEF. Cement composition and curing temperatures are the most influential of these factors.
Cement content is critical to the occurrence of SEF. Cements that react quickly and have high hydrating rates are more prone to SEF than moderate cements. Fast hydrating cements include cements that possess high C3A content, high SO3 content, high fineness properties, and high alkali content. Some researchers believe that a high SO3/Al2O3 ratio in cement is instrumental in causing SEF.
The type of aggregate used can is believed by many researchers to be influential in SEF occurrence. Since SEF often accompanies alkali-silica reaction (ASR), many researchers feel the use of reactive aggregates is prone to SEF. Reactive aggregates have an inferior silicate crystalline composition that allows the silica to be dissolved in solution of the concrete pore water over time.
Researchers generally agree that curing of concrete at elevated temperatures can lead to SEF. Precast concrete cured between 70° to 100°C is at high risk for SEF occurrence. A note must be made that several researchers believe that they have evidence of SEF occurring in normal cured concrete.