Expansion Due to DEF in Normally-Cured Concrete Heated by Cement Hydration

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Title: Expansion Due to DEF in Normally-Cured Concrete Heated by Cement Hydration

Author(s): N. Petrov, M. Thibault, and A. Tagnit-Hamou

Publication: Special Publication

Volume: 234

Issue:

Appears on pages(s): 239-250

Keywords: concrete; DEF; deterioration; ettringite; expansion; field concrete; heat of hydration; self-heating; steam curing; sulfate attack

Date: 3/22/2006

Abstract:
The expansion of laboratory heat-cured mortar and concrete specimens caused by delayed ettringite formation (DEF) is often the object of scientific investigation. However, cases of this expansion in normally-cured concrete are rarely reported in the literature. The results presented in this paper show that concretes made with a relatively moderate cement content of 300 kg/m3 can develop a temperature as high as 72 °C at the centre of massive elements, and that in such a case, it can be vulnerable to DEF and subsequent expansion. Four concrete mixtures made with different commercial cements having a W/C of 0.55, were used for casting cubic concrete samples measuring 0.2 m3. The temperature of fresh concrete was 30 °C. The maximum temperature developed at the centre of the samples varied between 64 and 72 °C. After 400 days of storage in lime-saturated water, two samples showed a significant expansion. One sample was severely cracked. This experiment shows that DEF-related expansion is not possible only in steam-cured precast concrete members, but that cast in-place massive concrete structures in hot climatic conditions can also be sensitive to DEF.