Assessment of damage in concrete cured at different temperatures caused by delayed ettringite formation

Reference	Presenter	Authors (Institution)	Abstract
04-066	Diego Jesus De Souza	De Souza, D.J.(University of Ottawa); Santos, V.A.(University of Ottawa); Sanchez, L.F.(University of Ottawa);	Delayed ettringite formation (DEF) along with alkali-aggregate reaction and steel corrosion is one of the most harmful distress mechanisms affecting concrete infrastructure worldwide. Several structures in France, Brazil and USA were already diagnosed with DEF and techniques for rehabilitating those structures are still under debate. DEF is assumed to be triggered once the concrete curing temperature is raised at above 65C. Important induced expansion, mechanical properties reductions and cracking patterns are often found while DEF development which may significantly reduce the short and long term performance of affected structures. In Canada, very likely due to its harsh and low temperature climate, DEF has never been seen as a major issue for concrete infrastructure. However, Canadian Standards Association (CSA) has recently allowed the curing temperature to be raised to 70C which might trigger DEF even in cold climates. This work studies the potential susceptibility of DEF to be generated while the use of the new CSA temperature curing guideline. Concrete mixtures were cast and cured under different high temperatures (80C and 70C) and placed in environments enabling DEF development. Expansion was monitored over time and microscopical (DRX, SEM, DRI and NMR) and mechanical (compressive, modulus of elasticity, SDT, etc.) tools were used to detect DEF damage as well as to compare its kinetics and distress potential and extent as a function of the curing temperature.
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