Radiation shielding performance of antimony oxide-modified concrete for 6 MV medical X-ray applications

The incorporation of high atomic number (high-Z) additives into concrete has been widely investigated as a potential approach to enhance radiation shielding performance. Among these materials, antimony oxide (Sb2O3) has demonstrated favorable photon attenuation characteristics in polymeric, glass, and composite systems. However, its behavior within cementitious matrices remains insufficiently understood. In this study, Sb2O3 was incorporated into conventional concrete as a partial replacement for standard sand at substitution ratios ranging from 0 to 20 wt% in order to evaluate the effects of Sb2O3 incorporation on physical, mechanical, and X-ray shielding properties. Experimental radiation attenuation measurements were performed using a medical linear accelerator (LINAC)-based ionization chamber system, while exposure buildup factor (EBF) and energy absorption buildup factor (EABF) were evaluated theoretically. Contrary to expectations based on the behavior of high-Z materials, the incorporation of Sb2O3 resulted in a systematic deterioration in concrete performance. The experimental results revealed that increasing Sb2O3 content led to a reduction in density, compressive strength, and X-ray attenuation capability when compared to reference concrete. Microstructural observations indicated that Sb2O3 interacts unfavorably with the cementitious matrix during hydration and curing, promoting increased porosity and weakened matrix cohesion, which adversely affected both mechanical integrity and radiation shielding efficiency. The findings clearly demonstrate that Sb2O3 is not a suitable additive for concrete from either a materials science or radiation shielding perspective. Despite its high atomic number, the incompatibility of Sb2O3 with cement-based systems results in inferior physical, mechanical, and radiological performance relative to conventional concrete. This study provides a critical caution against the direct adoption of high-Z shielding additives into cementitious materials without comprehensive evaluation of their chemical compatibility and structural consequences.