Improving the resistance of ultra-high-performance concrete against nuclear radiation: Replacing cement with barite, hematite, and lead powder

Abstract

Ultra-high-performance concrete (UHPC) is concrete with a high cement content; thus, replacing the cement with other materials can contribute to the sustainable production of UHPC. This type of concrete offers desirable strength characteristics and durability, which makes it a possible deterrent for countering gamma rays. The addition of sustainable materials can reduce the thickness of the protective concrete structures and possibly provide the desired attenuation and half-life coefficients. The current study used barite, hematite, and lead powders as replacements for cement at contents of 10%, 15%, 20%, 25%, and 30%. Compressive and flexural strength tests were performed at 28 days of age and X-ray diffraction (XRD) tests at 180 days of age. To determine the radiation attenuation and half-life coefficients, sodium iodide crystals were used with a gamma-ray spectrometer from three sources (137Cs, 60Co, and 207Bi) at energies of 662, 1173, and 1333 keV. The results showed that the replacement of cement with barite and hematite powder at all percentages reduced the compressive and flexural strengths of the concrete. Their highest compressive strengths were at 10% cement content (106 and 109 MPa, respectively). Replacement of cement with 20% lead powder provided the maximum compressive and flexural strengths of 129 and 13.5 MPa, respectively. XRD analysis showed that the reason for the high compressive strength with 20% lead powder was the increase in the resistance phases and the decrease in ettringite. The highest attenuation and lowest half-life coefficients were for UHPC with 30% lead powder (0.23 cm-1 and 3 cm, respectively). This was about 53% higher than that of the UHPC-only sample, and its half-life coefficient was 35% lower. Therefore, UHPC with 30% lead powder was the most efficacious mix design for resistance to gamma rays.