Determination of the Apparent Activation Energy of Concrete: Ea. Semi-Adiabatic Tests of Heat Development

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Title: Determination of the Apparent Activation Energy of Concrete: Ea. Semi-Adiabatic Tests of Heat Development

Author(s): L . D’Aloia and G. Chanvillard

Publication: Special Publication

Volume: 179

Issue:

Appears on pages(s): 561-586

Keywords: compressive strength; concrete; heat of hydration; maturity

Date: 6/1/1998

Abstract:
The N method of equivalent age )) is one of the currently used non-destructive testing methods of concrete strength estimation. It is based on the Arrhenius’ law, which has shown itself to be the most accurate in order to describe the influence of temperature on concrete strength development at early ages. A proper estimation is directly related to a correct determination of the Apparent Activation Energy : Ea. This is the unique parameter which characterizes the concrete mixture and which can be found in the Arrhenius’ law. The major aim of this paper is to show how calorimetric tests under semi-adiabatic conditions can be an alternative to unwieldy compressive tests procedures in order to determine Ea. The validity of the obtained Ea values has been verified by means of several mechanical tests. Moreover, the possibility of using either mortar or concrete is partially dealt with. The water to cement ratio appears to naturally be considered as a constant in proportioning an equivalent mortar. Finally, the evolution of the Apparent Activation Energy in relation to the degree of hydration is given. Hence, the widespread opinion that Ea depends on the degree of hydration is confirmed and a field of definition can be brought to the fore.