Investigating irradiation effects on metakaolin-based geopolymer

Abstract

Nuclear power facilities face a critical challenge: concrete deterioration caused by prolonged neutron irradiation. This study explores a promising alternative, a metakaolin-based potassium geopolymer, which was implanted with Ti+ ions to mimic the irradiation. We observed significant improvements in the geopolymer's mechanical properties after irradiation. Nanoindentation showed that microhardness increased by a remarkable 90 %, accompanied by a 46 % rise in reduced modulus and a 23 % reduction in contact depth. However, irradiation also induced surface cracking. Detailed characterization revealed microstructural changes, including the disappearance of unreacted metakaolin and densification of the geopolymer matrix. While X-ray diffraction showed no significant structural alterations, Fourier-transform infrared spectroscopy indicated a decrease in water content, and Raman spectroscopy revealed a reduction in intensity, peak shift, and an increase in full-width half maximum, suggesting the presence of titanium ions and potential modifications in the local chemical environment. This initial investigation paves the way for geopolymers to be environmentally friendly alternatives in nuclear reactor shielding. While our findings highlight promising mechanical property improvements after irradiation, further development is necessary to address crack mitigation. This study provides new insights to guide future optimization of geopolymer composition and microstructure for enhanced resistance to irradiation effects.