Contribution à la caractérisation des fines minérales et à la compréhension de leur rôle joué dans le comportement rhéologique des matrices cimentaires

Abstract

The objective of this work is to contribute to the comprehension of the principal mechanisms of action of mineral additives used in concrete. The use of mineral additives, coupled with superplasticizers, made it possible to significantly improve concrete mix design, concrete mechanical properties and durability. The first part deepen two characteristics of mineral additives (determination of the amorphous phase content by X ray diffraction and particle size distribution by laser granulometry) in order to increase their level of confidence. The second part highlights the effect of mineral additives on the rheological behaviour of cement pastes, then provides the first step in the way to understand their principal mechanisms of action. It is shown that: (1) the modification of the rheological parameters (yield stress and apparent viscosity) depends on physicochemical properties of the materials used (specific area, particle size distribution, composition), particularly when these properties modify compactness and interactions between particles. (2) the rheological behaviour of the pastes is not fundamentally modify by the use of mineral additives or by vibration, since these parameters only amplify or reduce the intensity of phenomenon like shear-thickening; on the contrary, superplasticizers have an important effect since their use lead to a gradual modification of the paste behaviour, which shift from shear-thinning to shear-thickening.