Abstract:
This paper presents a review of concrete deterioration due to delayed ettringite formation (DEF) including available test methods and guidelines to prevent deterioration of concrete due to DEF. Recently. severe cracking in some of the pile caps of bridge piers in the Southern Highway project was reported After extensive investigations, if was found that the main cause for cracking in those pile caps was DEF. DEF is sometimes referred to as internal sulphate attack which is an internal swelling reaction of the concrete that occurs in the presence of water without any external ingress of sulphate. Often DEF is associated with other deterioration mechanisms such as aggregate silica reaction (ASR).
Crack pauern due to both DEF and ASR are very similar and therejore it is difficult to identify the exact cause jor cracking without carrying out petrographic and SEM studies oj the affected concrete. Cracking due to DEF was originally reported in steam-cured concrete railway sleepers bUI it can also occur in large concrete pours where care
temperature can be very high as a result of heal of hydration It is widely accepted that concrete subjected 10 high temperature (> 70 °C) at early age and exposed to moisture continuously or intermittently after concrete has hardened is likely to crack due to DEF. Therefore this problem can occur in thick concrete members like pile caps. deep beams.
bridge piers and raft foundations. II was reported that the composition of cement especially C3A. SO) and alkali content can contribute to DEF induced cracking. II was also reported that apart from controlling maximum temperature rise in concrete and composition of cement, use of fly ash or slag blended cement is also effective in
preventing cracking due 10 DEF.
