Gamma shielding efficiency of sedimentary rock-based concrete blocks under Co-60 irradiation

Ensuring human safety requires understanding the radiation shielding capabilities of building materials alongside their strength and durability. Common conventional radiation shielding materials include lead and concrete. However, lead is costly, toxic, and raises environmental concerns, prompting increased interest in alternative shielding materials. Therefore, this research investigates the potential of concrete made from two types of sedimentary rocks, shale and calcareous, for shielding against Co-60 irradiation. The sedimentary rocks were sourced from the Global Geopark region in Satun Province, Thailand. The shielding performance of sedimentary rock-based concrete is compared with standard construction concrete. All concrete blocks were 15 cm × 15 cm × 15 cm and were prepared with a cement:sand:stone ratio of 1:2:4. Concrete cube specimens were prepared to evaluate radiation attenuation properties. The linear attenuation coefficient () was calculated from the reduction in count rate after transmission through the concrete block. Engineering properties, including density and compressive strength, were also analyzed. Radiation shielding efficiency is assessed using the linear attenuation coefficient (), mass attenuation coefficient (), mean free path (MFP), half-value layer (HVL), and tenth-value layer (TVL), All of these parameters were calculated from the measured count rates. The study found that standard concrete had the highest compressive strength at 25.45 MPa, followed by shale concrete at 13.59 MPa, and calcareous concrete at 5.21 MPa. However, shale concrete performed best in radiation shielding, showing a linear attenuation coefficient () of 0.18 cm⁻¹, a mass attenuation coefficient () of 0.09 cm²/g, a mean free path of 5.59 cm, a half-value layer of 3.87 cm, and a tenth-value layer of 12.86 cm. The improved shielding performance of shale concrete may be related to its mineral composition and internal structure. Analysis by XRD and XRF indicated that the main heavy metal compounds present were Al₂O₃ and Fe₂O₃.