A mathematical model for prediction of compressive strength in cement–silica fume blends.pdf

Cement and Concrete Research 34 (2004) 2319–2328A mathematical model for prediction of compressive strength in cement–silica fume blends J. Zelic?*, D. Rus?ic?, R. Krstulovic? Faculty of Chemical Technology, Department of Engineering and Technology, University of Split, Teslina 10/V, HR-21000 Split, CroatiaReceived 30 January 2003; accepted 9 April 2004Abstract In the present study, a mathematical model has been developed to predict cement properties from the description of hydration kinetics in Portland-slag cement–silica fume blends containing up to 15 mass % of silica fume. Knudsen’s dispersion models were applied in fitting both the degree of hydration and the compressive strength experimental data as a function of time. It was found that the ‘‘mixed (linear/ parabolic) dispersion model’’ fits the cement–silica fume blend systems well, as both the rate constants k1 and k2 of the Knudsen expressions are significant in the systems to which they are referring. With respect to the fact that there is a relationship between parameters as defined by Knudsen, this study has attempted to establish the direct functional dependence between the degree of hydration and the compressive strength by means of the time variable. It was found that the degree of hydration—the compressive strength dependence, for replacement levels varying from 0 to 15 mass % of silica fume, indicates a linear mathematical function. There are good agreements between the model and the experimentally obtained results. The proposed model provides the opportunity to predict the compressive strength development based on measuring the heat release during the 48-h cement hydration if the infinitely (ultimate) achievable compressive strength value is known.D 2004 Elsevier Ltd. All rights reserved.Keywords: Cement– silica fume blends; Hydration; Heat of hydration; Strength development; Modelling1. Introduction The development of strength of concrete is affected by many factors, such as cement composition and