An atomistic characterization of the interplay between composition, structure and mechanical properties of amorphous geopolymer binders

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

doi:10.1016/j.jnoncrysol.2015.11.022

Cited by 66 publications

(45 citation statements)

References 44 publications

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“…Figure 2 shows the equilibrium run in the The saturated structure, thus obtained, is then equilibrated for 400 ps in NPT ensemble and the statistical average is calculated for another 200 ps in NVT ensemble to obtain the final NASH structure with interlayer water as shown in Figure 3(a). For comparison purpose, a traditional NASH structure with random distribution of water (without any interlayer water), similar to the structures reported in literature 7,[36][37][38][39] is also generated. In this case, traditional method of assigning random position to all the atoms (Si, Al, Na and O) in the bounding box is followed keeping the values of the Si/Al ratio and Na/Al ratio 3 and 1 respectively.…”

Section: Model Constructionmentioning

confidence: 99%

“…As the significance of geopolymers gained more attention due to its environmental benefits, significant works have been focused on studying the local structure of alkali aluminosilicate gels (such as NASH gel) using various advanced materials characterization techniques such as x-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy [32][33][34][35] . In order to obtain detailed comprehensive insight on the local structural characteristics as well as the mechanical properties of such aluminosilicate gels, molecular dynamics (MD) simulations have been carried out 7,[36][37][38][39] . In these MD studies 7,[36][37][38][39] , the atomic structure of NASH gel has been constructed by traditional melt-quenching method 40,41 to obtain the amorphous sodium aluminosilicate glass (NAS) structure.…”

Section: Introductionmentioning

confidence: 99%

“…In order to obtain detailed comprehensive insight on the local structural characteristics as well as the mechanical properties of such aluminosilicate gels, molecular dynamics (MD) simulations have been carried out 7,[36][37][38][39] . In these MD studies 7,[36][37][38][39] , the atomic structure of NASH gel has been constructed by traditional melt-quenching method 40,41 to obtain the amorphous sodium aluminosilicate glass (NAS) structure. Finally, water is adsorbed randomly into the 3D glass (NAS) skeleton to obtain the wet NASH structure.…”

Section: Introductionmentioning

confidence: 99%

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Realistic atomic structure of fly ash-based geopolymer gels: Insights from molecular dynamics simulations

Lyngdoh

Kumar

Krishnan

et al. 2019

The Journal of Chemical Physics

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Geopolymers, synthesized through alkaline activation of aluminosilicates, have emerged as a sustainable alternative for traditional ordinary portland cement. In spite of the satisfactory mechanical performance and sustainability-related benefits, the large scale acceptance of geopolymers in the construction industry is still limited due to poor understanding of the composition-property relationships. Molecular simulation is a powerful tool to develop such relationships, provided the adopted molecular structure represents the experimental data effectively. Towards this end, this paper presents a new molecular structure of sodium aluminosilicate hydrate geopolymer gels, inspired from the traditional calcium silicate hydrates gel. In contrast to the existing model-where water is uniformly distributed in the structure-we present a layered-but-disordered structure. This new structure incorporates water in the interlayer space of aluminosilicate network. The structural features of the new proposed molecular structure are evaluated in terms of both short-and medium-range order features such as pair distribution functions, bond angle distributions, and structure factor. The structural features of the newly proposed molecular structure with interlayer water shows better correlation with the experimental observations as compared to the existing traditional structure signifying an increased plausibility of the proposed structure. The proposed structure can be adopted as a starting point towards realistic multiscale simulation-based design and development of geopolymers.

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Section: Model Constructionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Realistic atomic structure of fly ash-based geopolymer gels: Insights from molecular dynamics simulations

Lyngdoh

Kumar

Krishnan

et al. 2019

The Journal of Chemical Physics

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“…A theoretical investigation of reactivity is also discussed in this work by using theoretical reactivity indices based on the conceptual density functional theory (CDFT) 19,20 with the correlation-exchange functional (B3LYP) 21 on the basis 6-31G (d) level set 22 in the presence of the water solvent.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Silicate Gel by using Sol-gel Process: Experiments and DFT calculations

Chaair¹,

Driouich²,

Hassani³

et al. 2020

Mediterr.J.Chem.,

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The synthesis of geopolymers requires the formation of an irreversible gel. This gel is produced by the sol-gel process using sodium silicate and hydrochloric acid reagents. On the one hand, the experimental study of the gelling reaction shows that for concentrations of hydrochloric acid varying between 0.5-2.0 mol/L and concentration of sodium silicate varying between 1.0-6.0 mol/L, three reaction products are obtained. The first product is a clear solution, the second product is a reversible gel, and the last product is an irreversible gel. The products obtained are characterized by SEM, X-Ray Diffraction, FTIR spectroscopy and EDS Spectroscopy techniques. The microstructural analyzes of the two gels revealed that these obtained solids are almost similar whereas the structural and elementary analyzes show that the silica content in the irreversible gel is higher than the silica content in the reversible gel. On the other hand, the theoretical study of the reactivity of gelling, defined via the conceptual density functional theory (CDFT) combined with functional B3LYP function with a 6-31G base (d). They are allowed us to define the global and local reactivity indexes of two reagents, sodium silicate and hydrochloric acid.

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“…However, in the case (ii), a Si 4+ is substituted by Al 3+ , and thus substituted T n is an open shell system. Compare to our previous study where only one kind of substitution (iii) was studied, two more relevant [14] substitutions ((i) and (ii)) are studied and presented in this study.…”

Section: Introductionmentioning

confidence: 99%

The Role of Aluminum Substitution on the Stability of Substituted Polyhedral Oligomeric Silsesquioxanes

Asaduzzaman

Runge

Deymier

et al. 2016

Zeitschrift Für Physikalische Chemie

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A first principles density functional theory calculation has been carried out to study the energetics and structural properties of substituted polyhedral oligomeric silsesquioxane (POSS) as a function of the POSS cage size. The substitution of Si atom in the POSS molecules has been performed in three different ways, namely (i) both Si and an adjacent H atom are replaced by an Al atom, (ii) only a Si atom is replaced by an Al atom, and (iii) a Si atom is replaced by an Al and a Na/K atom. For the first and third kind of substitution, the net spin state is the same (i.e. closed shell), while the structures corresponding to the second kind of substitution are characterized by an excess spin (i.e. open shell). The structures of substituted POSS for the first and second kind of substitution are greatly distorted and always energetically less stable than the parent structure, while for the third kind of substitution, the stability depends on the cage size of POSS molecule, as also shown in a previous work (Asaduzzaman et al. [1]).

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An atomistic characterization of the interplay between composition, structure and mechanical properties of amorphous geopolymer binders

Cited by 66 publications

References 44 publications

Realistic atomic structure of fly ash-based geopolymer gels: Insights from molecular dynamics simulations

Realistic atomic structure of fly ash-based geopolymer gels: Insights from molecular dynamics simulations

Synthesis and Characterization of Silicate Gel by using Sol-gel Process: Experiments and DFT calculations

The Role of Aluminum Substitution on the Stability of Substituted Polyhedral Oligomeric Silsesquioxanes

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