Dissolution and Initial Hydration Behavior of Tricalcium Aluminate in Low Activity Sulfate Solutions

Published

January 22, 2020

Author(s)

Alexander Brand, Steven B. Feldman, Paul E. Stutzman, Anton V. Ievlev, Matthias Lorenz, Darren C. Pagan, Sriramya Nair, Justin Gorham, Jeffrey W. Bullard

Abstract

The effects on cubic tricalcium aluminate (C3A) hydration of alkali or alkaline earth sulfate electrolytes were evaluated by in situ dissolution rate measurements, by ex situ near-surface composition measurements with secondary ion mass spectrometry, and by in situ synchrotron X-ray diffraction to monitor precipitation of hydration products. Slight reductions in dissolution rate and cation-specific interactions with the solid are observed. The near- surface solid Ca/Al ratio is significantly lower after some dissolution, and the electrolyte cations adsorb to or penetrate the surface at different concentrations (Mg2+ > K+ > Na+), although an alternative mechanism by interfacial dissolution-reprecipitation is posited. The sulfate concentration affects the rates of both dissolution of C3A and the precipitation of hydration products. It is proposed that sulfate ions adsorb to the hydrous aluminum-rich layer at the C3A surface, which explains the observations that aluminate species dissolve more slowly, that the precipitation of aluminate hydration products is delayed, and that the continued growth of those products is slower in sulfate electrolytes than in pure water.

Citation

Cement and Concrete Research

Issue

130

Pub Type

Journals

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DOI Link

Keywords

kinetics, Ca3Al2O6, x-ray diffraction, hydration, dissolution

Citation

Brand, A. , Feldman, S. , Stutzman, P. , Ievlev, A. , Lorenz, M. , Pagan, D. , Nair, S. , Gorham, J. and Bullard, J. (2020), Dissolution and Initial Hydration Behavior of Tricalcium Aluminate in Low Activity Sulfate Solutions, Cement and Concrete Research, [online], https://doi.org/10.1016/j.cemconres.2020.105989 (Accessed November 21, 2024)