Evaluation of the effects of bismuth oxide (Bi2O3) micro and nanoparticles on the mechanical, microstructural and γ-ray/neutron shielding properties of Portland cement pastes

Abstract

This study presents a comparison of the effects of micro-Bi2O3 and nano-Bi2O3 powders on the mechanical, microstructural and gamma / neutron shielding properties of Portland cement pastes. Cement pastes with various ratios of cement (up to 30 wt-%) replaced with Bi2O3 micro and nanoparticles were prepared. Consistency, compressive strength, water accessible porosity and mercury intrusion porosimetry tests were performed, in order to characterize their engineering properties. In addition, experimental and theoretical evaluations of γ-ray and neutron shielding properties were performed. The results showed that the incorporation of Bi2O3 powders gradually leads to a decline in cement pastes’ compressive strength and an increase in their porosity, as the amount of powder is increased. However, the deterioration rate varies depending of type of powder used, in favor of nano-Bi2O3. Gamma attenuation tests results indicate that the addition of Bi2O3 powders enhances the shielding capability of pastes, in the energy range of interest (0.08–2.614 MeV). However, the effects of particle size on γ-ray attenuation are negligible in that energy range. Slow neutron attenuation study showed that the addition of nano-Bi2O3 improved the shielding ability of cement pastes, with enhancements ranging between 15.3% and 25.5% for samples with 5 and 30 wt-% nano-Bi2O3, respectively. In conclusion, this study shows that the addition of nano or micro-Bi2O3 is effective in producing lead-free cementitious composites with improved γ-ray and neutron shielding properties. Unlike gamma shielding, nano-sized Bi2O3 has a better ability to attenuate neutrons, in comparison to their micro-sized counterparts.