Estimating reaction kinetics of cementitious pastes containing fly ash

Glosser, Deborah; Suraneni, Prannoy; Isgor, O. Burkan; Weiss, Jason

doi:10.1016/j.cemconcomp.2020.103655

Cited by 44 publications

(17 citation statements)

References 51 publications

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“…In practice, most cementitious systems have not yet reached thermodynamic equilibrium. Kinetic models (such as the Parrot-Killoh model for OPCclinker [194] or the Modified Parrot-Killoh Model for clinker + SCM [195]) are often used to predict the mass fraction of the clinker that reacts at a given age. Thermodynamic models are often coupled with kinetic models to predict cementitious systems' reaction products at a given age.…”

Section: Kinetic Modelsmentioning

confidence: 99%

“…The Modified Parrot Killoh (MPK) model [195,196] was used to predict the mass fraction of the clinker phases (C3S, C2S, C3A, C4AF) and oxide phases in SCMs (SiO2, Al2O3, CaO) that react at a given age. The inputs to the MPK model are: (i) the chemical composition of the OPC-clinker and SCM used, (ii) the reactivity of the SCM (fraction of SCM that can react at equilibrium, usually the amorphous fraction of the SCM [196]), (iii) w/b, and, (iv) the temperature of curing.…”

Section: Modified Parrot Killoh Model For Clinker and Scmmentioning

confidence: 99%

See 1 more Smart Citation

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

Bharawadj¹,

Chopperla²,

Choudhary³

et al. 2021

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Section: Kinetic Modelsmentioning

confidence: 99%

Section: Modified Parrot Killoh Model For Clinker and Scmmentioning

confidence: 99%

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

Bharawadj¹,

Chopperla²,

Choudhary³

et al. 2021

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“…Thermodynamic modeling based on the minimization of Gibbs free energy is a powerful tool for assessing stable phase equilibria and equilibrium compositions of the solid and liquid (and gas) phases as relevant to encapsulation applications. However, the current implementations of such modeling often rely on assumptions including congruent dissolution of the fly ash and, most often, an inability to incorporate the actual degree of fly ash reaction which could be particularly affected in hypersaline environments that feature a reduced water activity. − For example, the dissolution rates of crystalline and amorphous materials could either enhance or decrease in hypersaline environments in relation to their compositions and concentrations. − For example, seawater has been suggested to enhance fly ash’s pozzolanic reactions . Since changes in reactivity alter not only the kinetics of reactions but also the phase assemblage that forms, it is important to assess these aspects due to the obvious implications on contaminant retention by the solidified waste forms.…”

Section: Introductionmentioning

confidence: 99%

Fly Ash–Ca(OH)₂ Reactivity in Hypersaline NaCl and CaCl₂ Brines

Collin

Prentice

Arnold

et al. 2021

ACS Sustainable Chem. Eng.

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The disposal of highly concentrated brines from coal power generation can be effectively accomplished by physical solidification and chemical stabilization (S&S) processes that utilize fly ashes as a reactant. Herein, pozzolanic fly ashes are typically combined with calcium-based additives to achieve S&S. While the reactions of fly ash–(cement)–water systems have been extensively studied, the reactivity of fly ashes in hypersaline brines (ionic strength, I m > 1 mol/L) is comparatively less understood. Therefore, the interactions of a Class C (Ca-rich) fly ash and a Class F (Ca-poor) fly ash were examined in the presence of Ca(OH)2, and their thermodynamic phase equilibria were modeled on contact with NaCl or CaCl2 brines for 0 ≤ I m ≤ 7.5 mol/L. At low ionic strengths (<0.3 mol/L), reactivity and stable phase assemblages remain effectively unaltered. However, at high(er) ionic strengths (>0.5 mol/L), the phase assemblage shows a particular abundance of Cl-AFm compounds (i.e., Kuzel’s and Friedel’s salts). Although formation of Kuzel’s and Friedel’s salts enhances the Class F fly ash reactions in both NaCl and CaCl2 brines, NaCl brines compromise Class C fly ash reactivity substantially, while CaCl2 results in the reactivity remaining essentially unchanged. Thermodynamic modeling that accounts for the fractional and noncongruent dissolution of the fly ashes indicates that their differences in reaction behavior are provoked by differences in the prevalent pore solution pH, which affects phase stability. The outcomes offer new insights for matching fly ashes, Ca additives, and brines, and accounting for and controlling fly ash–brine interactions as relevant to optimizing physical solidification and chemical stabilization applications.

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“…One of the reasons for the change in properties is the change in the chemical composition of the resulting composite. For cement composites, this is realized by binding portlandite to form various hydrosilicates [12][13][14][15][16]. To obtain a modified cement stone, it is advisable to use colloidal solutions of metal hydrosilicates [17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Chemical composition of nanomodified cement stone

Grishina

Korolev

2021

E3S Web Conf.

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Improving the properties of cement building materials is possible with the use of modifiers, including nanoscale ones. Such nanomodifiers include hydrosilicates of zinc and copper. The increase in the performance characteristics of nanomodified cement composites is due to changes in the chemical composition of the resulting cement stone, in particular, an increase in the content of hydrosilicate structures. The chemical composition of the cement stone was studied by FTIR-spectroscopy. Colloidal solutions of zinc and copper hydrosilicates with known characteristics were used for the nanomodification of cement stone. It is shown that when using copper hydrosilicates synthesized at high concentrations of iron hydroxide, the concentration of amorphous silica does not significantly affect the composition of cement stone. However, with a decrease in the concentration of iron hydroxide, with an increase in the concentration of amorphous silica, the content of hydrosilicate structures increases. The use of nanoscale zinc hydrosilicates is more efficient than copper hydrosilicates. Their use makes it possible to increase the content of structures containing silicon-oxygen tetrahedra, submicrocrystalline calcium hydrosilicates of a tobermorite-like structure in cement stone, and the formation of ettringite is also noted. Thus, it was found that the use of zinc hydrosilicates as nanomodifiers for cement stone allows increasing the content of hydrosilicate structures in hydration products.

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Estimating reaction kinetics of cementitious pastes containing fly ash

Cited by 44 publications

References 51 publications

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

Fly Ash–Ca(OH)₂ Reactivity in Hypersaline NaCl and CaCl₂ Brines

Chemical composition of nanomodified cement stone

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Estimating reaction kinetics of cementitious pastes containing fly ash

Cited by 44 publications

References 51 publications

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

CALTRANS: Impact of the Use of Portland-Limestone Cement on Concrete Performance as Plain or Reinforced Material

Fly Ash–Ca(OH)2 Reactivity in Hypersaline NaCl and CaCl2 Brines

Chemical composition of nanomodified cement stone

Contact Info

Product

Resources

About

Fly Ash–Ca(OH)₂ Reactivity in Hypersaline NaCl and CaCl₂ Brines