Effect of fineness on the pozzolanic reaction kinetics of slag in composite binders: Experiment and modelling

Abstract

In this study, the kinetics of the pozzolanic reaction of slag with various levels of fineness was characterized by experimental analysis and model simulation. The maximum reaction rate of ultrafine slag at the main pozzolanic reaction peak was found to be 67% larger than that of ordinary slag, with this gap becoming even larger (228%) at a high curing temperature. The early pozzolanic reaction degree was found to increase by 40%–60% due to increased slag fineness. At late ages, the pozzolanic reaction degree was still increased by approximately 40%–70% at room temperature but only by 20% at a high curing temperature due to increased slag fineness. The parameters for the kinetic model illustrate that slag fineness has little influence on the nucleation rate and linear growth rate of the product per unit surface area. However, the increase in the total surface area results in a large number of nuclei for the pozzolanic reaction products, leading to a large amount of product and a high reaction degree for ultrafine slag. The apparent activation energy for the pozzolanic reaction of ultrafine slag was found to be identical to that of ordinary slag, showing that an increase in slag fineness does not change the mechanism governing the pozzolanic reaction.