Proposed Structure for Calcium Silicate Hydrate Gel

Calcium silicate hydrate gel is a very poorly crystalline material that is the main product of reaction of portland cement with water. Evidence is presented for a disordered layer structure, in which most of the layers are structurally imperfect ones of jennite (Ca 9 Si 6 O 32 H 22 ), and others are similarly related to 1.4‐nm tobermorite (Ca 5 Si 6 O 26 H 18 ), both structures being modified by omission of many of their silicate tetrahedra. The evidence comprises conditions of formation, silicate anion type, Ca/Si ratio, H 2 O/Ca ratios and densities for various drying conditions, thermogravimetric curve, X‐ray powder and selected‐area electron diffraction patterns, and results of analytical electron microfcopy.