Case Studies in Construction Materials (Dec 2022)
Ionizing radiation shielding efficacy of common mortar and concrete used in Bangladeshi dwellings
Abstract
Ionizing radiation has become an integral component of modern scientific advancement. However, radiation can be harmful to human health if not shielded efficiently. Extensive research has been carried out to improve the shielding efficiencies of different construction materials, thereby leading to varying possible alternatives for future radiation-safe constructions. In contrast, the shielding capacities of existing structures and raw materials have received less attention, and no evaluation of the safety of the inhabitants in case of an emergency appears to have been conducted in Bangladesh. Therefore, this research aims to study the radiation shielding properties of ordinary mortar and concrete used in Bangladeshi dwellings. Three of the most used field concretes (1:1.25:2.5, 1:1.5:3, and 1:2:4) and mortar (1:3, 1:4, and 1:5) mixes are tailor-made for this purpose. Additional samples were prepared by partial replacement (15% and 30%) of cement in the media with ladle slag. The samples' transmission characteristics of 662 keV, 1173 keV, and 1332 keV gamma rays were measured using Co60 and Cs137 as radiation sources. A p-type, coaxial HPGe gamma-ray detector was used for this purpose, and each sample was tested for a consecutive period of 20000 s. Linear attenuation coefficient, mass attenuation coefficient, half value layer, tenth value layer, mean free path, and radiation protection efficiency are evaluated from the experimental results. Furthermore, the mechanical properties of concrete and mortar samples are determined. It is found that concrete with a field mix ratio of 1: 1.5: 3 offers better shielding at low energy, while 1: 1.25: 2.5 composition is more effective at higher energy. Similarly, 1:3 mortars are more effective for low energy, and 1:5 mortars provide better results for high energy radiation. However, the differences between the various concrete and mortar compositions are minimal. The ladle furnace slag slightly reduced the radiation shielding capacity of both mortar and concrete. The highest strength and lowest sorptivity were obtained for 1: 1.25: 2.5 concrete, whereas the opposite trend is observed for 1: 2: 4. On the other hand, 1: 3 and 1: 5 mortars show the highest and lowest compressive strength, respectively. No definite correlation between sample strength and shielding capacity can be established, although ultrasonic pulse velocity seems to be a good indicator in this case. Overall, conventional mortar and concrete used in infrastructure construction in Bangladesh show satisfactory results in shielding gamma rays in the energy range of 661–1332 keV.
