Nanostructure of Calcium Silicate Hydrate Gels in Cement Paste

Abstract

High‐resolution electron microscopy study of calcium silicate hydrate (C‐S‐H) gels in ordinary portland cement (OPC) and a slag/OPC blend has been performed. Nanocrystalline regions on the scale of ∼5 nm or less in C‐S‐H are found in both cement pastes, and they are formed after a curing time as brief as 7 d. A change in the d ‐spacing of the nanocrystalline regions with time is observed for the first time, which is believed to correspond to the development of C‐S‐H with time. The nanoheterogeneous nature of C‐S‐H is demonstrated and correlated to the strong Ca:Si ratio fluctuations that are observed.