Modeling of ionic interactions at the C-S-H surface. Application to CsCl and LiCl solutions in comparison with NaCl solutions

Title: Modeling of ionic interactions at the C-S-H surface. Application to CsCl and LiCl solutions in comparison with NaCl solutions
Author(s): Pierre Henocq, Jacques Marchand, Eric Samson, Jérôme-Alexandre Lavoie
Paper category : conference
Book title: 2nd International RILEM Symposium on Advances in Concrete through Science and Engineering
Editor(s): J. Marchand, B. Bissonnette, R. Gagné, M. Jolin and F. Paradis
Print-ISBN: 2-35158-003-6
e-ISBN: 2351580028
Publisher: RILEM Publications SARL
Publication year: 2006
Nb references: 23
Language: English

Abstract: Concrete structures can be exposed to various aggressive environments which cause significant degradations. In practice, different kinds of degradation are observed. Mostly, chemical degradations occur. The penetration of ionic species from the environment into the cementitious matrix induces chemical reactions which can seriously deteriorate the structural properties of concrete materials. The modelling of the ionic transport coupled with a dissolution/precipitation process gives reliable results. At constant temperature and constant relative humidity, transport of ions in porous medium is influenced by porosity, tortuosity and binding. Chemical binding is defined as being solid phase precipitation while physical binding is associated to the adsorption of ions at the hydrates surface. This paper focuses on the characterization of the physical binding in cementitious materials by modeling adsorption of ions at the surface of cement hydrates, especially calcium silicate hydrates (C-S-H). It is accepted that C-S-H mainly contribute to fix ions in solution, particularly because of their high specific surface area. Moreover, C-S-H have significant surface properties highlighting specific adsorption of ions. Calcium ions appear as being the potential determining ions; Ca2+ adsorption determines the surface charge of C-S-H. This adsorption is influenced by secondary ions, like alkali or chloride ions. This work presents the study of C-S-H and hydrated C3S samples in sodium chloride, cesium chloride and lithium chloride solutions. Analysis of solutions composition and zeta potential measurements made appear specific adsorption of Na+, Cs+, Li+ and Cl- ions. Chloride binding will be especially analysed. Binding properties seemed to be independent on the alkali cations. An interfacial modeling based on surface complexation will be shortly presented.

Keywords: C-S-H, binding, specific adsorption, C3S, modeling

Online publication: 2006-08-02
Classification: 3.1 Theme 1: Numerical Models: from Microstructure to Transport Properties and Durability
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580028.023