A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders

Mohammad Rafat Sadat, Stefan Bringuier, Abu Asaduzzaman, Krishna Muralidharan, Lianyang Zhang

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In this paper, molecular dynamics simulations are used to study the effect of molecular water and composition (Si/Al ratio) on the structure and mechanical properties of fully polymerized amorphous sodium aluminosilicate geopolymer binders. The X-ray pair distribution function for the simulated geopolymer binder phase showed good agreement with the experimentally determined structure in terms of bond lengths of the various atomic pairs. The elastic constants and ultimate tensile strength of the geopolymer binders were calculated as a function of water content and Si/Al ratio; while increasing the Si/Al ratio from one to three led to an increase in the respective values of the elastic stiffness and tensile strength, for a given Si/Al ratio, increasing the water content decreased the stiffness and strength of the binder phase. An atomic-scale analysis showed a direct correlation between water content and diffusion of alkali ions, resulting in the weakening of the AlO4 tetrahedral structure due to the migration of charge balancing alkali ions away from the tetrahedra, ultimately leading to failure. In the presence of water molecules, the diffusion behavior of alkali cations was found to be particularly anomalous, showing dynamic heterogeneity. This paper, for the first time, proves the efficacy of atomistic simulations for understanding the effect of water in geopolymer binders and can thus serve as a useful design tool for optimizing composition of geopolymers with improved mechanical properties.

Original languageEnglish (US)
Article number134706
JournalJournal of Chemical Physics
Volume145
Issue number13
DOIs
StatePublished - Oct 7 2016

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Geopolymers
moisture content
Binders
Molecular dynamics
alkalies
Mechanics
molecular dynamics
Alkalies
tensile strength
Water
stiffness
Water content
mechanical properties
water
Tensile strength
tetrahedrons
Stiffness
Ions
ions
elastic properties

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Sadat, Mohammad Rafat ; Bringuier, Stefan ; Asaduzzaman, Abu ; Muralidharan, Krishna ; Zhang, Lianyang. / A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders. In: Journal of Chemical Physics. 2016 ; Vol. 145, No. 13.
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A molecular dynamics study of the role of molecular water on the structure and mechanics of amorphous geopolymer binders. / Sadat, Mohammad Rafat; Bringuier, Stefan; Asaduzzaman, Abu; Muralidharan, Krishna; Zhang, Lianyang.

In: Journal of Chemical Physics, Vol. 145, No. 13, 134706, 07.10.2016.

Research output: Contribution to journalArticle

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