Title: Particle Interaction in Metakaolin Suspensions

Author(s): Sergio Real, Laura González-Panicello, Francisca Puertas, Marta Palacios

Publication: Symposium Paper

Volume: 362

Issue:

Appears on pages(s): 535-546

Keywords: metakaolin, superplasticizers, zeta potential, particle agglomeration, pore solution composition

DOI: 10.14359/51741009

Date: 6/14/2024

Abstract:
Limestone-calcined clay cements (LC³) have received a great deal of interest recently for their lower carbon footprint and suitable hardened properties. However, they are also characterized by having challenging rheological properties that lead to high water demands. While the addition of superplasticizers enhances their initial fluidity, they experience a fast flow loss, the mechanism of which still remains unknown. This study aims at gaining fundamental knowledge on the particle surface properties and colloidal stability in metakaolin suspensions, in the presence and absence of polycarboxylate-based superplasticizers. For this purpose, zeta potential, polymer adsorption, particle agglomeration as a function of time, and pore solution composition were evaluated. The experimental results revealed that an increase in pH up to 11 favors OH- adsorption, increasing the absolute zeta potential and therefore favoring interparticle repulsion. In contrast, above pH>11 a decrease of the absolute zeta potential and agglomeration was observed. Regarding the aqueous phase composition, a combination of Ca²⁺ and SO₄^2- in pore solutions at pH around 12.60, leads to particle agglomeration while the addition of 0.4% PCE superplasticizers efficiently disperse metakaolin particles in suspensions prepared with a synthetic cement pore solution.