Electrosteric control of the aggregation and yielding behavior of concentrated portlandite suspensions

Published

June 13, 2023

Author(s)

Sharu Kandy, Mathieu Bauchy, Gaurav Sant, Aditya Kumar, Narayanan Neithalath, Samanvaya Srivastava, Torben Gaedt, Edward Garboczi

Abstract

Portlandite (calcium hydroxide: CH: Ca(OH)2) suspensions aggregate spontaneously and form percolated fractal aggregate networks when dispersed in water. As a result, the yield stress and viscosity of portlandite suspensions diverge at low particle loadings, adversely affecting their processability. Even though polycarboxylate ether (PCE)-based comb polyelectrolytes are routinely used to alter the particle dispersion state, water demand and rheology of similar suspensions (e.g., Ordinary Portland Cement (OPC) suspensions) that feature a high pH and high ionic strength, their use to control portlandite suspension rheology has not been elucidated. This study combines adsorption isotherms and rheological measurements to elucidate the role of PCE composition (i.e., charge density, side chain length, and grafting density) in controlling the extent of PCE adsorption, particle flocculation, suspension yield stress, and thermal response of portlandite suspensions. We show that longer side chain PCEs are more effective in affecting suspension viscosity and yield stress, in spite of their lower adsorption saturation limit and fractional adsorption. The superior steric hindrance induced by the longer side chain PCEs results in better efficacy in mitigating particle aggregation even at low dosages. However, when dosed at optimal dosages (i.e., a dosage that induces a dynamically equilibrated dispersion state of particle aggregates), different PCE-dosed portlandite suspensions exhibit identical fractal structuring and rheological behavior regardless of the side chain length. Furthermore, it is shown that the unusual temperature-dependent rheological response of portlandite suspensions can be tailored by adjusting the PCE dosage. The ability of PCEs to modulate the rheology of aggregating charged particle suspensions can be generally extended to any colloidal suspensions with high ionic strength and strong charge screening behavior.

Citation

Langmuir

Volume

39

Pub Type

Journals

Download Paper

https://doi.org/10.1021/acs.langmuir.3c00704

Local Download

Keywords

Electrosteric repulsion, polycarboxylate ether, rheology, portlandite suspensions

Citation

Kandy, S. , Bauchy, M. , Sant, G. , Kumar, A. , Neithalath, N. , Srivastava, S. , Gaedt, T. and Garboczi, E. (2023), Electrosteric control of the aggregation and yielding behavior of concentrated portlandite suspensions, Langmuir, [online], https://doi.org/10.1021/acs.langmuir.3c00704, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=936307 (Accessed March 16, 2025)