Effects of high-temperature exposure on fractal dimension of fly-ash-based geopolymer composites

In this study, the microstructures of fly-ash-based geopolymer composites exposed to high temperatures were investigated by surface fractal dimension analysis. Geopolymer pastes with various Na2O contents were exposed to high temperatures. From the results, the mechanical and microstructural properties of geopolymer composites changed after thermal exposure. For the analysis of the microstructure, the surface fractal dimension was evaluated using the pore size distribution measured through MIP. As the temperature increased, the surface fractal dimension of the macropore region increased, but that of the micropore region decreased. After thermal exposure, the surface fractal dimension of the macropore regions showed a tendency to be proportional to the Na2O content, except for Na2O content of 4%. In the micropore region, there was no relationship with the Na2O content. It was found that compressive strength was proportional to the surface fractal dimension of the macropore region except for Na2O content of 4%. (C) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.orgnicensesiby-nc-nd/4.0/).