Abstract
Part I of this paper has reported the results of the experimental tests and discussed the influence of mineral additives on the hydration heat evolution. The purpose of the Part II of the paper is to study the validity of the equivalent age approach and determine the apparent activation energy of low clinker cements with mineral additives. The concept of the equivalent age method and Arrhenius formulation for the temperature sensitivity of the hydration reaction is briefly presented. The evolution of the apparent activation energy as well as its single values is determined on the basis of the tests results presented in Part I of the paper. The low clinker cements with 30, 50 and 70 % substitution ratio by ground granulated blast furnace slag or siliceous fly ash were studied. Finally, the results of semi-adiabatic and isothermal tests at different temperatures were compared to assess the validity of the equivalent age method with determined and recommended values of activation energy in relation to low clinker cements with mineral additives.
Highlights
As it was described in Part I of this paper, the heat released in concrete during its hardening process produces various thermomechanical effects
Part I of this paper has reported the results of the experimental tests and discussed the influence of mineral additives on the hydration heat evolution
The purpose of the Part II of the paper is to study the validity of the equivalent age approach and determine the apparent activation energy of low clinker cements with mineral additives
Summary
As it was described in Part I of this paper, the heat released in concrete during its hardening process produces various thermomechanical effects. The results of semi-adiabatic and isothermal tests at different temperatures were compared to assess the validity of the equivalent age method In this comparative analysis, the determined single value of the apparent activation energy and recommended values of activation energy have been compared. In the Arrhenius equivalent age function, the activation energy that defines the temperature sensitivity of the hydration reaction has to be determined. The activation energy (Fig. 1a) calculated on the basis of the Schindler’s approach is presented for the tested cements with different amounts of slag and fly ash. The RILEM recommendations [6, 8] for Portland cement and the Freiesleben Hansen and Pedersen definition [5] give basically the same value of the activation energy. This method is similar to the procedure contained in ASTM C 1074 reported in [14] and concluded as relatively easy
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