The effect that different pozzolanic activity methods has on the kinetic constants of the pozzolanic reaction in sugar cane straw-clay ash/lime systems:: Application of a kinetic-diffusive model

The reaction kinetics of a mixture of sugar cane straw with 20% and 30% of clay burned at 800 and 1000 degrees C and lime (calcium hydroxide) is studied. A direct method (accelerated chemical method) based on the measurement of the amount of lime reacted as the reaction proceeds is applied. A kinetic-diffusive model published in a previous paper by some authors of this research is used. The fitting of the model by computerized methods allows determining the kinetic coefficients that characterize the process: in particular, the reaction rate constant. The index of pozzolanic activity evaluated according to the obtained values of the reaction rate constant permits to characterize the pozzolanic activity of these materials in a rigorous way. The results are compared with the results obtained applying an indirect method (conductometric method). The kinetic results obtained in the current paper allow affin-ning that the kinetic-diffuse model used in order to evaluate the pozzolanic reaction is valid, independently of the method used for the evaluation of the pozzolanic activity. (C) 2005 Elsevier Ltd. All rights reserved.