Delayed ettringite formation in Swedish concrete railroad ties

A petrographic examination of cracked Swedish concrete railroad ties identified delayed ettringite formation (DEF) as the damaging mechanism. This was unexpected because the concrete railroad ties were steam-cured with a maximum concrete temperature below 60 °C. The consensus in the published literature is that DEF only occurs in concrete subjected to heat curing above 70 °C. However, DEF is not only influenced by the curing temperature, but also by various other factors, such as cement composition (alkalis, C 3S, C 3A, SO 3, and MgO), fineness, etc. If an unfavorable combination of these parameters exists, delayed ettringite may occur at lower temperatures than 70 °C. In this paper, the influence of various parameters on DEF is discussed with reference to the investigated concrete.