EFFECT OF MAGNETITE AND COLEMANITE ON RADIATION SHIELDING ULTRA-HIGH-PERFORMANCE CONCRETE

Abstract

Concrete containment structures play a critical safety role in nuclear infrastructure. However, conventional radiation shielding concrete (RSC) exhibits limited design strength, reinforcement congestion, and durability issues. This study develops a novel radiation shielding ultra-high-performance concrete (RS-UHPC) incorporating magnetite and colemanite aggregates. A control UHPC mixture was tailored using particle packing optimization, and magnetite and colemanite contents were systematically varied using a statistical experimental design. A spectrum of RS-UHPC designs were formulated and evaluated for density, compressive strength, and radiation attenuation (i.e., gamma, fast neutron, and thermal neutron). Results demonstrated that full replacement of silica sand with magnetite significantly enhanced mechanical and gamma shielding properties, while achieving the highest density (3420 kg/m³, a 41% improvement), linear attenuation coefficient (0.260 cm⁻¹, a 38% improvement), and fast neutron removal cross-section (0.119 cm⁻¹, a 23% improvement). Colemanite, while slightly reducing compressive strength, improved thermal neutron shielding by 130%. The combination of magnetite and colemanite (at 100% magnetite replacement of silica sand and 7% colemanite replacement of cement) exhibited the highest shielding properties, achieving 21 and 161% increases in fast and thermal neutron attenuations, respectively. To balance strength and shielding performance, an optimal mix was developed with 100% magnetite and 5.25% colemanite, achieving 120 MPa compressive strength while maintaining significant radiation attenuation. The use of such optimized mixture as shielding material enables the construction of thinner, safer nuclear containment structures. Moreover, recommendations are made to further enhance the developed RS-UHPC mixture. The findings of this study contribute to the advancement of RS-UHPC as a high-performance shielding material for nuclear applications.