Sugar cane wastes as pozzolanic materials: applications of mathematical model

Abstract

This paper proposes a kinetic-diffusive model that allows for determination of pozzolanic activity as related to optimum calcining temperature on the activation of wastes from sugar cane industries and their use as pozzolanic material. Research based on the reaction kinetics between lime (calcium hydroxide [CH]), sugar cane straw ash (SCSA), and sugar cane bagasse ash (SCBA) calcined at 800 and 1000 °C (1472 and 1842 °F) is described. A pozzolanic activity method (accelerated chemical method) based on the measurement of the amount of CH reacted as the reaction proceeds is applied and the latter on the kinetic parameters are quantified by applying a kinetic-diffusive model to the process. The kinetic parameters that characterize the process (in particular, the reaction rate constant and free energy of activation) were determined with relative accuracy in the fitting process of the model. The pozzolanic activity is quantitatively evaluated according to the obtained values of the kinetic parameters. The results show good pozzolanic properties of the sugar cane wastes between 800 and 1000 °C (1472 and 1832 °F), and no influence of the calcining temperature on the pozzolanic activity for SCSA was observed. The correlation between the values of free energy of activation ΔG# and the reaction rate constants K are in correspondence with the theoretical studies about the rate processes reported in the literature.