Experimental and theoretical evidence of overcharging of calcium silicate hydrate

Summary, in English

Electrokinetic measurements such as electrophoresis may show an inversion of the effective surface charge of colloidal particle called overcharging. This phenomenon has been studied by various theoretical approaches but up to now very few attempts of confrontation between theory and experiment have been conducted. In this work we report electrophoretic measurements as well as Monte Carlo simulations of the electrokinetic potential for the surf ice of calcium silicate hydrate (C-S-H), which is the major constituent of hydrated cement. In the simulations, the surface charge of C-S-H nanoparticles in equilibrium with the ionic solution is determined by a single site characteristic and electrostatic interactions between all explicit charges at the surface and in the electric double layer. We will show that ordinary electrostatic interactions are enough to describe all experimental observations. Actually, an excellent agreement is found between experimental and simulated results without any fitting parameter, both with respect to surface titration and electrokinetic behaviour. The agreement extends over a wide range of electrostatic coupling, from a weakly charged surface with mainly monovalent counter-ions to a highly charged one with divalent counter-ions. (C) 2007 Elsevier Inc. All rights reserved.

• Author: Christophe Labbez; Andre Nonat; Isabelle Pochard; Bo Jönsson
• Department/s: Computational Chemistry
• Publishing year: 2007
• Language: English
• Pages: 303-307
• Publication/Series: Journal of Colloid and Interface Science
• Volume: 309
• Issue: 2
• Links: http://dx.doi.org/10.1016/j.jcis.2007.02.048
• Document type: Journal article
• Publisher: Academic Press
• Topic: Theoretical Chemistry (including Computational Chemistry)
• Keywords: surface; Monte Carlo simulation; overcharging; calcium silicate hydrate; charge titration; zeta potential
• Status: Published
• ISBN/ISSN/Other: ISSN: 1095-7103