Mechanisms of dispersion of metakaolin particles via adsorption of sodium naphthalene sulfonate formaldehyde polymer

Maryam H Derkani; Nathan J Bartlett; Gaone Koma; Laura A Carter; Daniel A Geddes; John L Provis; Brant Walkley

doi:10.1016/j.jcis.2022.07.166

Mechanisms of dispersion of metakaolin particles via adsorption of sodium naphthalene sulfonate formaldehyde polymer

J Colloid Interface Sci. 2022 Dec 15;628(Pt B):745-757. doi: 10.1016/j.jcis.2022.07.166. Epub 2022 Jul 29.

Authors

Maryam H Derkani¹, Nathan J Bartlett², Gaone Koma³, Laura A Carter⁴, Daniel A Geddes⁵, John L Provis⁶, Brant Walkley⁷

Affiliations

¹ Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK; Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK; Hazelwood Chemical Synthesis, The Lubrizol Corporation, The Knowle, Nether Lane, Hazelwood, Derbyshire DE56 4AN, UK. Electronic address: m.derkani@sheffield.ac.uk.
² Hazelwood Chemical Synthesis, The Lubrizol Corporation, The Knowle, Nether Lane, Hazelwood, Derbyshire DE56 4AN, UK. Electronic address: nathan.bartlett@lubrizol.com.
³ Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
⁴ Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
⁵ Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK; Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK.
⁶ Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK. Electronic address: j.provis@sheffield.ac.uk.
⁷ Department of Chemical and Biological Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield S1 3JD, UK. Electronic address: b.walkley@sheffield.ac.uk.

PMID: 36027784
DOI: 10.1016/j.jcis.2022.07.166

Abstract

The influence of different alkali and alkaline earth cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺), and of solution pH, on surface interactions of metakaolin particles with a sodium naphthalene sulfonate formaldehyde polymer (SNSFP) (a commercial superplasticizer for concretes) was investigated in aqueous systems relevant to alkali-activated and blended Portland cements. This study used zeta potential measurements, adsorption experiments, and both in situ and ex situ Fourier transform infrared spectroscopy measurements of the suspensions to gain a fundamental understanding of colloidal interactions and physicochemical mechanisms governing dispersion in this system. SNSFP was most effective in dispersing metakaolin suspensions in Ca²⁺-modified aqueous NaOH systems (CaCl₂-NaOH) at dosages of 5 wt.%. Additionally, Ca²⁺ was the most effective alkaline earth cation mediator in providing a dispersion effect in metakaolin dispersed in aqueous NaOH and SNSFP mixtures, while Mg²⁺ was the most effective in aqueous KOH and SNSFP mixtures. The colloidal dispersion remained stable in the highly alkaline environment, and therefore SNSFP could be utilized to improve dispersion of metakaolin-based alkali-activated systems. The suggested mechanism for colloidal stability and fluidity of metakaolin-based cements (e.g. Portland cement blends and alkali-activated cements) is explained by changes in the distribution and structure of the electric double-layer, as well as structural forces, due to alteration in surface charge density and hydrated shell, facilitating competitive adsorption of the polymer.

Keywords: Alkali-activated cement; Calcined clay; Dispersion mechanisms; Geopolymer cement; Metakaolin; Portland cement; Sodium naphthalene sulfonate formaldehyde polymer; Total organic carbon content; Zeta potential.