Unveiling the synergistic effects of Ilmenite and Ferroboron on the radiation shielding properties of ultra-high-performance concrete

By coupling exception mechanical and durability merits with radiation shielding characteristics, radiation shielding ultra-high-performance concrete (RS-UHPC) promises to foster nuclear safety and security. In this study, a novel RS-UHPC was developed by leveraging the synergistic effects of Ilmenite and Ferroboron as replacements for Quartz Sand. To this end, particle packing was optimized using the Modified Andersen & Andreasen model (MAA), while a simplex centroid design was implemented to capture the separate and joint effects of Quartz Sand, Ilmenite, and Ferroboron on the physical, mechanical, and radiation shielding properties of RS-UHPC. A total of 13 mixture designs, 9 for model establishment and 4 for verification, were developed. Density and compressive strength were experimentally determined, while radiation shielding parameters, including linear attenuation coefficient ( µ ), mass attenuation coefficient ( µ m ), thermal neutron capture cross-section ( ∑ abs ), and effective removal macroscopic cross-section ( ∑ R ), were analytically evaluated. The developed RS-UHPC mixtures achieved densities up to 3196 kg/m 3 and compressive strengths up to 125 MPa, while using a deliberately selected higher water-to-binder ratio that, despite slightly reducing mechanical properties, it significantly enhanced neutron attenuation efficiency. Model adequacy was verified, and mixture optimization based on a pre-defined desirability function tailored for nuclear applications identified an optimal ternary system of 28 % Quartz Sand, 22 % Ilmenite, and 50 % Ferroboron. Compared to the reference mixture, the optimized mixture improved the density, linear attenuation ( µ ), and fast neutron effective macroscopic removal cross-section ( ∑ R ) by 31 %, 28 %, and 24 %, respectively, while achieving a remarkable enhancement in thermal neutron capture cross-section ( ∑ abs ) exceeding 1,600 %, owing to the high boron content. These findings contribute to propel the discovery of advanced shielding materials needed for fostering nuclear safety and security.