Determining the "apparent" activation energy of concrete Ea-numerical simulations of the heat of hydration of cement

The "apparent activation energy" of concrete-E-a-is usually determined by means of mechanical or calorimetric tests. This parameter, which characterises the sensitivity of concrete hydration processes to temperature, is required for estimating the compressive strength of concrete at early age by the "method of equivalent age." The major aim of this paper is to show how numerical simulations of released heat under adiabatic conditions could be an alternative to experiments for determining E-a. The simulation model-the CHAL program-which is developed here, is based on the kinetic model of Avrami-Erofeev. The coupling by temperature between the different chemical reactions of the main anhydrous components of cement is taken into account by using the Arrhenius' law. The model leads to a better understanding of the polymineral characteristic of cement as regards heat of hydration and E-a determination. The "apparent" nature of E-a and its dependence on hydration degree can be underlined. (C) 2002 Elsevier Science Ltd. All rights reserved.