The Importance of Interfacial Chemistry on the Strength of Slowly-Reacting Fly Ash-Cement Composites

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Title: The Importance of Interfacial Chemistry on the Strength of Slowly-Reacting Fly Ash-Cement Composites

Author(s): Konrad Krakowiak

Publication: Web Session

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Date: 10/23/2022

Abstract:
Despite the large number of studies on supplementary cementitious materials, the under-lying physicochemical interfacial processes that govern their strength remain obscure. To address this knowledge gap, this work strives to establish a relation between the chemical composition of fly ash (FA) at the molecular level and the macroscopic compressive strength in cement hydrates-FA composites. We develop a multiscale modeling framework that links the fundamental physicochemical attributes of calcium silicate hydrate (C-S-H)-FA interfaces across molecular (~1 nm), mesoscopic (~100 nm), and microscopic (~10 µm) length scales. We observe that FA's chemical composition affects the interfacial properties across all scales. FAs with higher network-modifier cation concentration show stronger molecular and mesoscale interfacial properties and statistically significant higher macroscopic compressive strength. This is particularly interesting for Class F FA, where early-age reactivity is negligible.




  


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