Nanomechanical characterization of ambient-cured fly ash geopolymers containing nanosilica

Abstract

The elastic modulus, hardness, and volume fractions of different phases of ambient-cured fly ash (FA) geopolymers were determined using the nanoindentation method. A low-calcium FA was blended with either 15% GGBFS or 10% OPC to accelerate curing and the effect of 2% nanosilica (NS) was studied. It was found that the inclusion of NS increased the volume of reaction product from 70% to 79% and reduced the porous phase from 13% to 7% in the FA only geopolymer. Similar changes were also found in the OPC or GGBFS blended geopolymer specimens. The reduction of the porous phase correlated well with the porosity determined by mercury intrusion porosimetry tests. Thus, the improvement in the properties of ambient-cured geopolymers by the inclusion of NS was established using the nanoindentation characterization.

Keywords:

• nanoindentation
• geopolymer
• hardness
• elastic modulus
• mercury intrusion porosimetry

Acknowledgments

The authors acknowledge that the manuscript is an integral part of the first author’s PhD thesis submitted at Curtin University, Australia. The authors wish to gratefully acknowledge the support of Coogee Chemicals, Western Australia for supplying the chemicals used in this study.

Conflict of interest

No potential conflict of interest was reported by the authors.