Coupled thermodynamic modelling and experimental study of sodium hydroxide activated slag

Abstract

In previous researches, the thermodynamic modelling of alkali-activated slag was conducted as a function of the degree of reaction of slag, which makes it difficult to compare the modelling results with the experimental results in a time scale. In this study, the reaction kinetics of sodium hydroxide activated slag was studied using isothermal calorimetry and quantified using the Ginstling-Brounshtein equation. With the quantified reaction kinetics, the hydration of slag was thermodynamically modelled in a time scale. Based on the thermodynamically modelled phase assemblage, chemical shrinkage and phase evolution were derived as a function of time.Besides the isothermal calorimetry, a series of experimental techniques were used to evaluate the thermodynamic modelling results. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to investigate the pore solution composition. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to study the reaction products. Energy-dispersive X-ray spectroscopy (EDX) was used to examine the elemental composition of reaction products. The experimental results were presented, discussed, and used to evaluate the thermodynamic modelling results in terms of pore solution composition and reaction products. The modelled pore solution composition matched the experimentally measured data within ± 1 order of magnitude. The thermodynamic modelling and experimental results were in agreement regarding bound water, type and amounts of reaction products.