Surface free energy evaluation of building materials

Courard Luc 1Frédéric Michel 

1. University of Liege (ULg), B5, Liège 4000, Belgium

Abstract

The surface free energies and their components between two interacting surfaces are extremely important since not only do they dictate the strength of interaction, but also control processes like the stability of aqueous colloidal suspensions, wetting, spreading and adhesion. The interactions solid-liquid are mainly controlled by the interfacial surface tensions between the two phases. The characterization of the surface properties and especially the surface free energy components of the solid are, therefore, recognized as the key to understanding the mechanism of surface-based phenomena.

Concrete is a very complex material, not only what about concerns composition but also its evolution with time. As concrete can be considered as a colloidal suspension when in fresh state, surface interactions will firstly act on the dispersion of particles inside the concrete mix and promote the fluidity of the fresh material. The superplasticizers and Modifying Viscosity Agent are fundamental components, particularly for the development of Self Consolidating Concrete.

Another area of surface tensions action is the interface between formwork and cement paste. As the superficial layer of concrete is a critical zone with higher W/C ratio and defaults like air bubbles, it is also important to understand the basic phenomenons that will act on the quality of the surface and to select the most appropriate materials to avoid these defaults. Air is always present in fresh concrete and the aim of vibration techniques or textiles applied on the formwork is to prevent the formation or the stabilisation of the air bubbles in the surface layer of concrete. Data are needed to evaluate correctly the surface free energies of liquids and solids present in this three phases mix: air, cement paste, formwork.

Finally, concrete repair quality is based on interactions between old concrete and new material, at the levels of the creation and the stability of the interface.

Presentation: poster at E-MRS Fall Meeting 2005, Symposium G, by Courard Luc
See On-line Journal of E-MRS Fall Meeting 2005

Submitted: 2005-05-19 06:25
Revised:   2009-06-07 00:44
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