EFFECT OF ILMENITE AND FERROBORON ON RADIATION SHIELDING ULTRA-HIGH-PERFORMANCE CONCRETE

Abstract

The rapid expansion of Canada’s nuclear energy sector requires new facility construction while ensuring compliance with the highest safety and security standards. Concrete serves as the primary physical barrier in nuclear infrastructure, shielding against radiation and preventing leakage into the environment and public spaces during normal operational conditions as well in the event of accidents. Consequently, nuclear facility safety depends on the quality of concrete used. This research focuses on developing radiation shielding ultra-high-performance concrete (RS-UHPC) with enhanced mechanical and radiation shielding properties. First, a state-of-the-art review identified Ilmenite and Ferroboron—both rarely studied in the literature—as promising aggregates due to their high densities, heavy atomic element content, and Ferroboron's elevated boron levels necessary for neutron shielding. Subsequently, an extensive experimental program was designed to assess the individual and combined effects of partially replacing Quartz Sand with Ilmenite and Ferroboron (up to 50% each) on RS-UHPC’s physical, mechanical, and radiation shielding properties. We coupled particle packing optimization with statistical modeling to capture the optimal compositional domain space that balances mechanical performance with radiation shielding characteristics. A relatively high water-to-binder ratio of 0.25 was intentionally implemented to serve dual functions: providing sufficient hydrogen content for fast neutron moderation while maintaining optimal mixture flowability. The Modified Andreasen & Andreasen model was applied to maximize particle packing density, enhancing mixture compactness. The Simplex Centroid Design enabled capturing the separate and joint interaction effects of Ilmenite and Ferroboron on RS-UHPC performance. Results indicated that while these aggregates slightly reduced compressive strength, they significantly improved radiation shielding, yielding 33%, 1,200%, and 25% enhancements for v gamma, thermal neutron, and fast neutron shielding, respectively. Based on pre-defined desirability criteria considering nuclear-grade UHPC, the optimal compositional domain space lies at 26% Quartz Sand, 24% Ilmenite, and 50% Ferroboron. These findings constitute a significant leap forward in engineering novel concrete formulations with enhanced mechanical performance and radiation shielding, thereby contributing to the deployment of safer and more secure nuclear facilities.