Effect of incorporating hematite on the properties of ultra-high performance concrete including nuclear radiation resistance

Radiation is one of the most important problems for nuclear power plants. To fulfill the urgent need for building materials with high radiation resistance and improved mechanical and durability properties, a novel anti-radiation ultra-high-performance concrete (UHPC) was designed. This was accomplished by using hematite powder to partially replace natural river sand at different replacement ratios. A series of tests were conducted, addressing fresh concrete's fluidity, hardened concrete's compressive strengths at room and elevated temperatures, impact strength, chloride resistance, radiation resistance, micropore structure, and hydration products. Experimental results show that the addition of hematite slightly decreased the work performance and compressive strength of UHPC, but substantially increased its flexural and impact strength and showed satisfactory high-temperature performance. The gamma-ray shielding performance of hematite UHPC was substantially enhanced by increasing the hematite replacement ratio. Compared with ordinary concrete, the linear attenuation coefficient of the UHPC with a 40% hematite replacement ratio increased by 43%, and the half-value layer thickness was reduced by 30%. The addition of hematite powder did not change the types of cement hydration products, but did improve the internal micropore structure, and cause the UHPC to exhibit excellent chloride ion penetration resistance.