A new model for the C-S-H phase formed during the hydration of Portland cements

By E. Gartner, I. Maruyama, Jeffrey J. Chen. 2017

176 citations recorded by the source corpus.

Abstract A model is developed to explain why the C-S-H phase that grows during the hydration of Portland Cements initially requires a high water content, much of which is lost by gentle drying. It is proposed that the rapid growth of C-S-H during the hydration of alite (C3S) in Portland cements initially occurs by adsorption of fully hydrated aqueous calcium cations onto anhydrous anionic basal sheets of a silicate-deficient (dimeric) tobermorite-like composition. Both divalent (Ca2 +) and univalent (CaOH+) solvated cations are incorporated to balance the negative charge of the basal sheet, leading to significant structural disorder, explaining the poorly-crystalline nature of the C-S-H formed. Some of the solvation water is lost irreversibly on first drying due to the formation of Si-O-Ca-O-Si bridges, explaining irreversible shrinkage. The initially-formed C-S-H is metastable relative to a form with longer silicate chains, towards which it may slowly evolve with separation of water and CH.

Subfields: Civil and Structural Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/d1f9a1919a46a919887dc82048fad490564c5b99