Characterising the reaction of metakaolin in an alkaline environment by XPS, and time- and spatially-resolved FTIR spectroscopy

Abstract

The process of the dissolution of metakaolin in an alkaline environment remains incompletely understood; there are many mechanistic details which still require elucidation. Here, we apply X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to provide new information regarding the bonding environments in the altered layer on the surface of a metakaolin particle in contact with different alkali hydroxide solutions (Li, Na and K as alkali cations, and concentrations ranging from 1-8 mol/L). The use of photoacoustic infrared spectroscopy enables the collection of spectra as a function of depth into the particle, and these are compared with surface-sensitive attenuated total reflectance FTIR spectra. In parallel, chemical state plots derived from XPS spectra provide new insight into the evolution of bonding environments of the silicon and aluminium atoms comprising the altered layer on the metakaolin surface.