Thixotropy of superplasticized cement pastes – Underlying mechanisms considering the polycarboxylate molecular structure, interparticle interactions and hydration kinetics

Nicia D, Jakob C, Jansen D, Ivanov D, Mazanec O, Dengler J, Neubauer J, Lowke D (2023)

Publication Type: Journal article

Publication year: 2023

Journal

Cement and Concrete Research Elsevier

Book Volume: 173

Article Number: 107289

DOI: 10.1016/j.cemconres.2023.107289

Abstract

This paper deals with the decisive mechanisms of thixotropic structural build-up in superplasticized cement-based suspensions related to the PCE molecular structure. We investigate the effect of the side chain length and anionic charge ratio of tailored PCE superplasticizers on thixotropic structural build-up under quantitative consideration of colloidal and contact interactions as well as very early hydration kinetics. The thixotropic structural build-up of superplasticized cement pastes with systematically varying the PCE molecular structure was investigated at constant workability, i.e. dynamic yield stress, by adjusting the individual PCE dosage. Thixotropy was quantified using plate-plate rheometry, while at the same time superplasticizer adsorption, specific surface area, granulometric measurements and quantitative XRD analysis provided an experimental basis for the identification of the respective contribution to the structural build-up. Our results show that the thixotropic structural build-up increases with decreasing PCE side chain length and increasing anionic charge ratio. This is due to accelerated very early hydration kinetics, causing an increase in the specific surface area. The latter is primarily attributed to ettringite, modifying the particle size distribution of the hydrated cement paste. Our approach of separating the colloidal and contact interactions indicates that the PCE-induced change in particle size distribution due to accelerated ettringite formation as well as the change in the average effective layer thickness are the dominant mechanisms for the thixotropic structural build-up in this context.

Authors with CRIS profile

Cordula Jakob Lehrstuhl für Mineralogie Daniel Jansen Lehrstuhl für Mineralogie Jürgen Neubauer Lehrstuhl für Mineralogie

Involved external institutions

Technische Universität Braunschweig DE Germany (DE) Master Builders Solutions Deutschland GmbH DE Germany (DE) BASF SE DE Germany (DE)

How to cite

APA:

Nicia, D., Jakob, C., Jansen, D., Ivanov, D., Mazanec, O., Dengler, J.,... Lowke, D. (2023). Thixotropy of superplasticized cement pastes – Underlying mechanisms considering the polycarboxylate molecular structure, interparticle interactions and hydration kinetics. Cement and Concrete Research, 173. https://doi.org/10.1016/j.cemconres.2023.107289

MLA:

Nicia, David, et al. "Thixotropy of superplasticized cement pastes – Underlying mechanisms considering the polycarboxylate molecular structure, interparticle interactions and hydration kinetics." Cement and Concrete Research 173 (2023).

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