title: Dynamical behaviors of structural, constrained and free water in calcium- and magnesium-silicate-hydrate gels.
abstract: OBJECTIVE
  The mechanical properties of cement pastes depend strongly on their porosities. In a saturated paste, the porosity links to the free water volume after hydration. Structural water, constrained water, and free water have different dynamical behavior. Hence, it should be possible to extract information on pore system by exploiting the water dynamics.
  
  
  METHODS
  We investigated the slow dynamics of hydration water confined in calcium- and magnesium-silicate-hydrate (C-S-H and M-S-H) gels using high-resolution quasi-elastic neutron scattering (QENS) technique. C-S-H and M-S-H are the chemical binders present in calcium rich and magnesium rich cements. We measured three M-S-H samples: pure M-S-H, M-S-H with aluminum-silicate nanotubes (ASN), and M-S-H with carboxyl group functionalized ASN (ASN-COOH). A C-S-H sample with the same water content (i.e. 0.3) is also studied for comparison.
  
  
  RESULTS
  Structural water in the gels contributes to the elastic component of the QENS spectrum, while constrained water and free water contribute the quasi-elastic component. The quantitative analysis suggests that the three components vary for different samples and indicate the variance in the system porosity, which controls the mechanical properties of cement pastes.
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: lepeisi@mit.edu.
authors.forename: Peisi
authors.initials: P
authors.lastname: Le
authors.affiliation: Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, Sesto Fiorentino, Florence I-50019, Italy. Electronic address: fratini@csgi.unifi.it.
authors.forename: Emiliano
authors.initials: E
authors.lastname: Fratini
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: kanae@mit.edu.
authors.forename: Kanae
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: zwang10@mit.edu.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA. Electronic address: mamontove@ornl.gov.
authors.forename: Eugene
authors.initials: E
authors.lastname: Mamontov
authors.affiliation: Department of Chemistry "Ugo Schiff" and CSGI, University of Florence, Sesto Fiorentino, Florence I-50019, Italy. Electronic address: baglioni@csgi.unifi.it.
authors.forename: Piero
authors.initials: P
authors.lastname: Baglioni
authors.affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: sowhsin@mit.edu.
authors.forename: Sow-Hsin
authors.initials: SH
authors.lastname: Chen
keywords: Calcium-silicate-hydrate; Magnesium-silicate-hydrate; Porous material; Quasi-elastic neutron scattering; Water dynamics