ABSTRACT
T. KISHI and K. MAEKAWA Engineering Research Institute, Civil Engineering, The University of Tokyo, Japan
Abstract This paper aims at developing a predictive method on both heat generation and associated evolution of strength for young concrete. Mineral compounds of cement clinker and pozzolans are focused and the hydration degree of them are computed step by step with modified Anhenius's law of chemical reaction. The specific free water and calcium hydro-oxide, that is an activator for pozzolans, are assigned as state variables representing chemical environment of pore solution. The effect of fly ash on cement and slag hydration retarded by the adsorption of calcium ion is taken into account. The strength and instantaneous stiffness of hardening concrete are related to the accumulated heat of each mineral compound and versatility of the mechanical model proposed is verified under varying temperature environments. Kevwords: Clinker Minerals, Slag, Fly ash. Hydration, Heat Generation
1 Introduction
For making thermally induced cracks avoidable, evaluation of thermal crack risk is required at design stage. Here, the hydration heat of cement in concrete has to be modeled as a source of temperature rise. Meanwhile, the strength and stiffness evolution of concrete should be also predicted for examining thermal crack occurrence. The heat generation and varying mechanica properties of concrete at early ages are strongly related to the hydration degree of each mineral compound consisting of cement. Thus, it is desired to consistently predict them with a unified concept concerning hydration progress of cement. This approach brings an engineering advantage to enable sensitivity analysis with respect to mix proportion of concrete and sorts of cement and pozzolans with different chemical compositions and blended ratios.
