OBSERVATION OF A MESOSTRUCTURE IN CALCIUM SILICATE HYDRATE GELS OF PORTLAND-CEMENT

Transmission electron microscopy studies of calcium silicate hydrate ( C-S-H) gels in portland cement have been performed. This is the first study which unambigiously demonstrates the presence of a mesostructure in the C-S-H gel phase. The mesostructure was found to consist of an amorphous matrix with a strongly variable composition which was embedd ed with nanocrystalline regions on the scale of similar to 50 Angstrom or less each with a locally homogeneous composition and with short-ra nge ordered regions on the scale of similar to 10 Angstrom with a vari able composition and structure. The mesostructure is believed to form due to the inability of normal long-range crystallinity to evolve beca use of gross fluctuations in the local Ca/Si ratio.