Effects of Na2O/SiO2 molar ratio on properties of aggregate-paste interphase in fly ash-based geopolymer mixtures through multiscale measurements

Mahdieh Khedmati, Hani Alanazi, Yong Rak Kim, Gabriel Nsengiyumva, Sussan Moussavi

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

This paper presents a multiscale experimental study on the influence of different Na2O/SiO2 molar ratios on the mechanical and microstructural characteristics of the aggregate-paste interphase in fly ash-based geopolymer mixtures. By analyzing the scanning electron microscope images, the solid phases present in the microstructure were identified, and the frequency of occurrence of each phase was quantified. In addition, the porosity and pore size distribution of geopolymer specimens were measured by mercury intrusion porosimetry. By conducting nanoindentation tests on a large array of indentations and subsequent statistical analysis of the test results, the elastic moduli of individual phases were extracted. The bond behavior between aggregate and paste was also investigated by conducting the three-point bending test of single edge notched beam specimens. Integration of test results in different length scales showed that interphase region generates more sodium aluminosilicate hydrate (i.e., N-A-S-H) gel than the adjacent paste region regardless of the Na2O/SiO2 ratios used in this study. In addition, the mixture prepared with the higher Na2O/SiO2 molar ratio exhibited more N-A-S-H gel in the interphase zone, which led to increased bonding strength between aggregate and paste.

Original languageEnglish (US)
Pages (from-to)564-574
Number of pages11
JournalConstruction and Building Materials
Volume191
DOIs
StatePublished - Dec 10 2018

Fingerprint

Coal Ash
Geopolymers
Ointments
Fly ash
Gels
Adhesive pastes
Aluminosilicates
Bending tests
Nanoindentation
Hydrates
Indentation
Pore size
Statistical methods
Electron microscopes
Porosity
Elastic moduli
Mercury
Sodium
Scanning
Microstructure

Keywords

  • Fly ash-based geopolymer
  • Interphase
  • Microstructure
  • Multiscale
  • NaO/SiO molar ratio
  • Nanomechanical properties

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)

Cite this

Effects of Na2O/SiO2 molar ratio on properties of aggregate-paste interphase in fly ash-based geopolymer mixtures through multiscale measurements. / Khedmati, Mahdieh; Alanazi, Hani; Kim, Yong Rak; Nsengiyumva, Gabriel; Moussavi, Sussan.

In: Construction and Building Materials, Vol. 191, 10.12.2018, p. 564-574.

Research output: Contribution to journalArticle

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