Topological controls on the dissolution kinetics of glassy aluminosilicates

Area of Science:

• Materials Science
• Civil Engineering
• Geochemistry

Background:

• Fly ash is a common supplementary cementitious material (SCM) used to replace ordinary portland cement (OPC) in concrete.
• Higher replacement levels of OPC with fly ash are desirable for economic and environmental reasons.
• Quantifying fly ash reactivity is crucial for optimizing its use in concrete.

Purpose of the Study:

• To investigate the factors controlling the reactivity of glassy fractions in fly ash.
• To establish a relationship between the atomic structure and the dissolution rate of fly ash.
• To develop a framework for predicting fly ash-cement interactions in concrete.

Main Methods:

• Utilized molecular dynamics (MD) simulations to model the atomic structure of fly ash.
• Employed vertical scanning interferometry (VSI) to measure the aqueous dissolution rates.
• Analyzed the topological constraints on atoms within the aluminosilicate network.

Main Results:

• Fly ash reactivity, specifically its aqueous dissolution rate, is governed by the number of constraints on atoms in the glassy aluminosilicate network.
• An Arrhenius-like relationship was observed between dissolution rates and the atomic network topology.
• This topological control was demonstrated across various U.S. commercial fly ashes with different compositions.

Conclusions:

• The atomic structure, or topology, of glassy fly ash dictates its reactivity with water.
• This finding provides a structure-property relationship to better control and estimate fly ash performance in concrete.
• The study offers an improved framework for utilizing fly ash as an SCM in concrete.