The role of nanopores in concrete

Title: The role of nanopores in concrete
Author(s): J. Adolphs
Paper category : conference
Book title: International RILEM Workshop on Frost Resistance of Concrete
Editor(s): M. J. Setzer, R. Auberg and H. - J. Keck
Print-ISBN: 2-912143-30-6
e-ISBN: 2351580370
Publisher: RILEM Publications SARL
Publication year: 2002
Pages: 45 - 52
Total Pages: 8
Nb references: 8
Language: English

Abstract: Hardened cement paste (hcp), the "glue" of concrete performs a porous heterogeneous material consisting of dispersed particles like calcium silicate hydrates (C-S-H). The size of these solid particles ranges between microns and nanometers forming pores on a nanometer scale. Thus, hcp can be regarded as a colloidal system. Three different sized groups of nanopores can be distinguished for a fully hardened cement paste. This paper discusses the various physical and mechanical aspects of these groups of nanopores. Apparently, sorption and capillary condensation phenomena play a vital role, with respect to surface and interface properties. Adsorbed water molecules decrease the sur-face free energy and induce swelling. Capillary condensation occurs in the pores below bulk conditions, and capillary and disjoining forces are acting. Consequently the porous structure is altered and a series of other properties, all depending on the moisture content. One important feature is the transport capability for gases. Various experiments will be introduced and discussed, conducted over the entire range of relative humidity including water vapour and nitrogen sorption, mercury intrusion porosimetry, measurement of the contact angle, and water vapour transport. The humidity dependent behaviour is non-linear and often characterised by an extreme value in the medium range of humidity.

Online publication: 2010-06-28
Publication type : full_text
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