CA X-RAY-ABSORPTION SPECTROSCOPY OF C-S-H AND SOME MODEL COMPOUNDS

Calcium K-edge (4038 eV) X-ray absorption spectroscopy (XAS) of wet an d dry Ca-silicate hydrate (C-S-H) samples and model compounds (calcite , xonotlite, 11 Angstrom tobermorite, and 14 Angstrom tobermorite) sho w that the local structure of single-phase C-S-H as viewed from the Ca -positions is similar to that of tobermorite. The only major effect of wetting and drying observed by Ca-XAS is an increase in the average C a-Ca distance, probably due to changes in interlayer spacing. The Ca-X AS spectrum of a fully hydrated beta-C2S sample, containing C-S-H and portlandite, is significantly different due to the presence of the por tlandite. Ca-XAS provides unique information about the structure of C- S-H and is likely to be a useful tool for investigating the structures of a wide range of phases of importance to cement science.