title: Investigation of the surface structure and elastic properties of calcium silicate hydrates at the nanoscale.
abstract: This work is the first step towards the understanding of the structure of calcium silicate hydrate (C-S-H), the main constituent of cement paste, at the nanoscale. The first demonstration of atomic-resolution imaging of the (C-S-H) surface with an atomic force microscope (AFM) was performed. C-S-H nanoparticles (60 x 30 x 5 nm3) were partially recrystallized by Ostwald ripening after long-term equilibrium in saturated calcium hydroxide solution of different concentration, leading to C-S-H of different calcium/silicon ratio (Ca/Si). The results of atomic resolution made possible the investigation of the C-S-H cell surface parameters. The surface layer structure depended on the calcium hydroxide concentration with which it equilibrated. The change in structural properties perpendicular to the C-S-H layer was probed by modifying AFM for nanoindentation hardness measurements with a depth of indentation as low as 1 nm. The change in elastic modulus depending on the calcium/silicon ratio was evaluated and correlated in the change in structural parameters in this direction as estimated by X-ray diffraction.
authors.affiliation: Physics Laboratory LPUB, UMR CNRS 5027, University of Bourgogne, F-21078 Dijon, France.
authors.forename: Cédric
authors.initials: C
authors.lastname: Plassard
authors.forename: Eric
authors.initials: E
authors.lastname: Lesniewska
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pochard
authors.forename: André
authors.initials: A
authors.lastname: Nonat