Article abstract
Nature Materials 6, 311 - 316 (2007)
Published online: 25 March 2007 | doi:10.1038/nmat1871
Subject Categories: Structural materials | Characterisation and analytical techniques
Composition and density of nanoscale calcium–silicate–hydrate in cement
Andrew J. Allen1, Jeffrey J. Thomas2 & Hamlin M. Jennings2,3
Abstract
Although Portland cement concrete is the world's most widely used manufactured material, basic questions persist regarding its internal structure and water content, and their effect on concrete behaviour. Here, for the first time without recourse to drying methods, we measure the composition and solid density of the principal binding reaction product of cement hydration, calcium–silicate–hydrate (C–S–H) gel, one of the most complex of all gels. We also quantify a nanoscale calcium hydroxide phase that coexists with C–S–H gel. By combining small-angle neutron and X-ray scattering data, and by exploiting the hydrogen/deuterium neutron isotope effect both in water and methanol, we determine the mean formula and mass density of the nanoscale C–S–H gel particles in hydrating cement. We show that the formula, (CaO)1.7(SiO2)(H2O)1.80, and density, 2.604 Mg m-3, differ from previous values for C–S–H gel, associated with specific drying conditions. Whereas previous studies have classified water within C–S–H gel by how tightly it is bound, in this study we classify water by its location—with implications for defining the chemically active (C–S–H) surface area within cement, and for predicting concrete properties.
- Ceramics Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois 60208, USA
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA
Correspondence to: Andrew J. Allen1 e-mail: andrew.allen@nist.gov
MORE ARTICLES LIKE THIS
These links to content published by NPG are automatically generated.
NEWS AND VIEWS
Human therapeutic proteins from silkwormsNature Biotechnology Research News (01 Jan 2003)
RESEARCH
Microstructure of Hydrated Portland Cement PastesNature Letters to Editor (05 Sep 1970)
X-ray-scattering information obtained from near-field speckleNature Physics Article (01 Mar 2008)
Electron Microprobe Studies of the Hydration of 3CaO.SiO 2Nature Letters to Editor (02 Aug 1969)
See all 12 matches for Research
