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Relating the nanostructure of concrete to engineering properties

Title: Relating the nanostructure of concrete to engineering properties
Author(s): Hamlin M. Jennings, Jeffrey J. Thomas, Julia S. Gevrenov, Georgios Constantinides, Franz-Josef Ulm
Paper category : conference
Book title: NICOM 2: 2nd International Symposium on Nanotechnology in Construction
Editor(s): Y. de Miguel, A. Porro and P.J.M. Bartos
Print-ISBN: 2-912143-87-X
e-ISBN: 2912143888
Publisher: RILEM Publications SARL
Publication year: 2006
Pages: 57 - 66
Total Pages: 10
Nb references: 14
Language: English

Abstract: The engineering properties of concrete depend closely upon the structure of the cement paste hydration products, particularly the nanostructure of the calcium silicate hydrate (C-S-H) gel. Progress in understanding and quantifying structure-property relationships for concrete have been hampered by the fact that the C-S-H gel is extraordinarily difficult to quantitatively characterize. In recent years, advanced and novel characterization methods such as small-angle neutron scattering, nanoindentation, and volume changes during equilibrium drying have provided new information about the C-S-H gel, and this has led to the development and refinement of a quantitative structural model of the nanostructure of C-S-H. According to the model, a key feature of the structure of C-S-H is the presence of regions of different density that arise due to different packing densities of the same fundamental nanometer-scale particles of C-S-H.
In this paper an extension to the C-S-H model is presented that accounts for structural changes that occur upon aging, heating, and drying of concrete. Irreversible length changes are shown to be due to changes in porosity of a loose-packed (LP) C-S-H that forms initially. With the passage of time, or following the application of elevated temperature or drying, the LP C-S-H densifies to approach a stable random jammed packing of globules, called low-density (LD) C-S-H. The modified model provides a new physical basis for modeling bulk drying shrinkage, and the development of similar relationships for other engineering properties such as creep can be envisioned.

Online publication: 2005-11-17
Publication type : full_text
Public price (Euros): 0.00

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