The Interaction between Monosulfoaluminate and Calcium Chloride Aqueous Solution

Abstract

Scanning transmission X-ray microscope (STXM) and Ca L2,3-edge near-edge X-ray Absorption structure (NEXAFS) spectra investigate simultaneously the morphological and chemical information of various cement-based materials. The interaction between calcium chloride and monosulfoaluminate and the validation of intermediate phases were investigated. As the concentration of CaCl2 solution increases, calcium monosulfoaluminate (Ms) is converted into ettringite, Kuzel's salt (Ks) and Friedel's salt (Fs) in varying degree, while SO42- units in the ettringite and Kuzel's salt are continuously replaced by Cl2- in the solution, eventually forming Fs and gypsum. Based on Ca L2,3-edge NEXAFS absorption spectra, ettringite, Ms, Ks and Ms were greatly distinguished by the number and the shape of the leading peaks in the spectra since the difference in SO42- content among the interlayer structure of Ms, Ks and Fs. The present work is based on the references for the STXM study of the calcium (sulfo)aluminates, for demonstrating a more complete understanding of the phase evolution under chloride environments.