TY - JOUR
T1 - Effects of Na2O/SiO2 molar ratio on properties of aggregate-paste interphase in fly ash-based geopolymer mixtures through multiscale measurements
AU - Khedmati, Mahdieh
AU - Alanazi, Hani
AU - Kim, Yong Rak
AU - Nsengiyumva, Gabriel
AU - Moussavi, Sussan
N1 - Funding Information:
The authors are grateful for the financial support received from the National Science Foundation (Grant No. CMMI-1635055 ). We also like to acknowledge testing facilities: The Nano-Engineering Research Core Facility (NERCF) and the Nebraska Center of Materials and Nanoscience (NCMN) at the University of Nebraska-Lincoln to conduct the laboratory tests for this study.
Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/12/10
Y1 - 2018/12/10
N2 - 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.
AB - 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.
KW - Fly ash-based geopolymer
KW - Interphase
KW - Microstructure
KW - Multiscale
KW - NaO/SiO molar ratio
KW - Nanomechanical properties
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U2 - 10.1016/j.conbuildmat.2018.10.024
DO - 10.1016/j.conbuildmat.2018.10.024
M3 - Article
AN - SCOPUS:85054654080
VL - 191
SP - 564
EP - 574
JO - Construction and Building Materials
JF - Construction and Building Materials
SN - 0950-0618
ER -