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Compositionally Diverse Calcium-Sili...

Keiser, Debra Ann,

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Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling // Debra Ann Keiser.
Author:	Keiser, Debra Ann,
Description:	1 electronic resource (420 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
Contained By:	Dissertations Abstracts International86-12B.
Subject:	Computational chemistry. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32002604
ISBN:	9798280748446

Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling /
Keiser, Debra Ann,

Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling /Debra Ann Keiser. - 1 electronic resource (420 pages)

Source: Dissertations Abstracts International, Volume: 86-12, Section: B.

Ordinary Portland cement (OPC) is a core component of concrete, yet its manufacturing contributes significantly to carbon dioxide emissions worldwide. Efforts to mitigate the negative environmental impact of OPC production include partially replacing OPC with supplementary cementitious materials (SCMs) that encompass non-negligible amounts of aluminum and sodium. Substitution of OPC with SCMs improves the sustainability of the resulting concrete; however, the chemistry of calcium-silicate-hydrate (C-S-H) gel, which is the main hydration phase of OPC and strength-giving phase of concrete, changes. Modifications to the composition of C-S-H greatly influence C-S-H gel properties and may have important implications for the resistance of concrete against chemical attack. Hence, this dissertation focuses on the multi-scale modeling of calcium-rich and silicon-rich C-S-H and its variations, namely calcium-aluminate-silicate-hydrate (C-A-S-H) and sodium-containing C-A-S-H (C-(N-)A-S-H), along with interactions between these cementitious gels and anions known to facilitate concrete degradation. Bulk representations of C-S-H, C-A-S-H, and C-(N-)A-S-H that have variable elemental ratios and structural features are first generated using force field molecular dynamics. Resultant models are characterized by computing coordination numbers, bond angle distributions, and pair distribution functions (PDFs). Unsupervised machine learning algorithms involving dimensionality reduction and clustering are then employed to identify and classify the local silicon- and aluminum-centric atomic environments that constitute each model. Cluster validation indices were primarily utilized to assess the quality of every clustering solution. The medoids or closest data points (i.e., atomic environments) to the centers of select clusters formed the bases of calcium silicate substructures that undergo density functional theory (DFT) calculations. Complexing substructures with Cl-, SO42-, and CO32- ions supplies valuable insight into mechanisms of ion sorption by way of binding energies and Mulliken population analyses. Bulk C-S-H, C-A-S-H, and C-(N-)A-S-H models are also expanded to create interfacial systems that separately comprise aqueous sodium chloride, sodium sulfate, and calcium carbonate. Force field molecular dynamics simulations of these systems are carried out to determine average mean-squared displacements (MSDs), diffusion coefficients, density profiles, and coordination numbers of atoms and molecules therein, providing a comprehensive understanding of how gel chemistry affects anion behavior and adsorption.

English

ISBN: 9798280748446Subjects--Topical Terms:

3350019
Computational chemistry.
Subjects--Index Terms:

Calcium-silicate-hydrate

Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling /
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245 1 0 $a Compositionally Diverse Calcium-Silicate-Hydrate Gel Structures and Ion Adsorption Mechanisms Studied Through Molecular Modeling / $c Debra Ann Keiser.
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500 $a Source: Dissertations Abstracts International, Volume: 86-12, Section: B.
500 $a Advisors: White, Claire E. Committee members: Selloni, Annabella; Bourg, Ian C.; Schoop, Leslie M.
502 $b Ph.D. $c Princeton University $d 2025.
520 $a Ordinary Portland cement (OPC) is a core component of concrete, yet its manufacturing contributes significantly to carbon dioxide emissions worldwide. Efforts to mitigate the negative environmental impact of OPC production include partially replacing OPC with supplementary cementitious materials (SCMs) that encompass non-negligible amounts of aluminum and sodium. Substitution of OPC with SCMs improves the sustainability of the resulting concrete; however, the chemistry of calcium-silicate-hydrate (C-S-H) gel, which is the main hydration phase of OPC and strength-giving phase of concrete, changes. Modifications to the composition of C-S-H greatly influence C-S-H gel properties and may have important implications for the resistance of concrete against chemical attack. Hence, this dissertation focuses on the multi-scale modeling of calcium-rich and silicon-rich C-S-H and its variations, namely calcium-aluminate-silicate-hydrate (C-A-S-H) and sodium-containing C-A-S-H (C-(N-)A-S-H), along with interactions between these cementitious gels and anions known to facilitate concrete degradation. Bulk representations of C-S-H, C-A-S-H, and C-(N-)A-S-H that have variable elemental ratios and structural features are first generated using force field molecular dynamics. Resultant models are characterized by computing coordination numbers, bond angle distributions, and pair distribution functions (PDFs). Unsupervised machine learning algorithms involving dimensionality reduction and clustering are then employed to identify and classify the local silicon- and aluminum-centric atomic environments that constitute each model. Cluster validation indices were primarily utilized to assess the quality of every clustering solution. The medoids or closest data points (i.e., atomic environments) to the centers of select clusters formed the bases of calcium silicate substructures that undergo density functional theory (DFT) calculations. Complexing substructures with Cl-, SO42-, and CO32- ions supplies valuable insight into mechanisms of ion sorption by way of binding energies and Mulliken population analyses. Bulk C-S-H, C-A-S-H, and C-(N-)A-S-H models are also expanded to create interfacial systems that separately comprise aqueous sodium chloride, sodium sulfate, and calcium carbonate. Force field molecular dynamics simulations of these systems are carried out to determine average mean-squared displacements (MSDs), diffusion coefficients, density profiles, and coordination numbers of atoms and molecules therein, providing a comprehensive understanding of how gel chemistry affects anion behavior and adsorption.
546 $a English
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650 4 $a Materials science. $3 543314
650 4 $a Chemistry. $3 516420
650 4 $a Molecular chemistry. $3 1071612
653 $a Calcium-silicate-hydrate
653 $a Density functional theory
653 $a Ion adsorption
653 $a Molecular dynamics
653 $a Molecular modeling
653 $a Unsupervised learning
690 $a 0219
690 $a 0794
690 $a 0431
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710 2 $a Princeton University. $b Chemistry. $e degree granting institution. $3 3823544
720 1 $a White, Claire E. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 86-12B.
790 $a 0181
791 $a Ph.D.
792 $a 2025
856 4 0 $u https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=32002604