Extended X-ray Absorption Fine Structure Investigation of Calcium Silicate Hydrates

²⁹Si MAS-NMR, and Ca-EXAFS experiments have been conducted on calcium silicate hydrates (C-S-Hs) with structure derived from wollastonite. Crystalline compounds (wollastonite, xonotlite, hillebrandite, foshagite, 1.1 nm and 1.4 nm tobermorites, and jennite) and C-S-H were synthesized and characterized. ²⁹Si NMR provides information on silicate chains and EXAFS on calcium environment. The refined EXAFS values are in agreement with XRD data, except for tobermorite. The calcium order in C-S-H (C/S molar ratio from 0.7 to 1.4) is similar to that of tobermorite but different from that of jennite. Structural models of C-S-H are discussed.