Delayed Ettringite Formation in Concrete: Tests Based on Drying and Wetting Cycles

摘要

Delayed ettringite formation (DEF) is an endogenous reaction which can cause deterioration in concrete. At the present time, there is no selective and predictive test for DEF. This paper describes the results of a study aimed at developing a test based on drying and wetting cycles. Concrete specimens were manufactured and then either subjected to heat treatment at 80℃ or conserved at 20℃. Next, these specimens were either subjected to one of the two tests we have evaluated or immersed in water without undergoing the drying and wetting cycles beforehand. The two predictive tests we have studied are based on cycles of drying (at 38℃ or 60℃) and wetting (at 23℃) followed by continuous immersion in water (at 23℃). On the basis of expansion measurements and Scanning Electron Microscope examinations we have been able to: 1. describe a reduction in the selectivity of the test when drying was conducted at 60℃, 2. identify concretes which are potential victims of DEF when drying is conducted at 38℃. A predictive test on concrete with regard to DEF which is based on drying and wetting cycles therefore becomes a possibility when drying is conducted at 38℃.