Effects of high temperatures to mechanical and gamma ray shielding properties of radiation shielding concrete with Serpentine and Ascharite aggregate

As a key material for the shielding structures of nuclear facilities, optimizing the performance and understanding the mechanisms of radiation shielding concrete has attracted considerable attention. In this study, magnetite was used as coarse aggregate, while serpentine and ascharite were used as fine aggregates respectively. The performance of the resulting normal-strength radiation shielding concrete was evaluated under different temperature ranges (24 °C, 100 °C, 300 °C, 500 °C, 600 °C, and 800 °C), focusing on parameters such as mass loss, ultrasonic non-destructive testing, compressive strength, and gamma-ray shielding capacity. The mechanisms of thermal damage and the evolution of performance in magnetite-serpentine and magnetite-ascharite concrete under high temperatures were analyzed. It was found that the residual compressive strengths of magnetite-serpentine and magnetite-ascharite at 800 °C were 28.3 and 40.2 MPa, respectively, and their linear attenuation coefficients decreased to 88.2 % and 89.5 % of their values at room temperature. The results indicate that magnetite–ascharite concrete exhibits superior thermal stability, structural integrity, mechanical toughness, and radiation shielding performance across various temperatures compared to magnetite–serpentine concrete. The results can provide scientific guidance for the design of shielding structures for reactors, nuclear waste placement and treatment, etc. Multi-parameter correlation heatmap analysis confirmed that ultrasonic pulse velocity is an effective indicator for evaluating thermal damage in concrete, which provides a basis for quantitative detection of concrete thermal damage by ultrasonic properties.