Gamma radiation shielding properties of slag and fly ash-based geopolymers

Industrial waste-based geopolymer cement is a greener alternative to Ordinary Portland Cement (OPC) for radiation shielding with comparable mechanical properties without the production of CO₂ during synthesis. In this paper, the linear attenuation coefficient of slag and fly ash-based geopolymers, unmodified by aggregates, is measured and used to calculate the mass attenuation coefficients, half-value layer (HVL), and tenth-value layer (TVL) of the geopolymers. Narrow Beam Gamma Spectrometry with gamma energy of 0.662 MeV, 1.173 MeV, and 1.332 MeV was used to irradiate a series of slag and fly ash-based geopolymer paste of cylindrical shape with a diameter of 7.5 cm and height of 9.5 cm. Slag geopolymer has linear attenuation coefficient of 0.1642/cm, 0.1237/cm, 0.1150/cm, mass attenuation coefficient of 0.0782 cm²/g, 0.0589 cm²/g, 0.0548 cm²/g, the HVL of 4.222 cm, 5.609 cm, 6.056 cm, and TVL of 14.025 cm, 18.633 cm, 20.118 cm, respectively. Fly ash geopolymer has linear attenuation coefficient of 0.1387/cm, 0.1075/cm, and 0.0964/cm, mass attenuation coefficient of 0.0761 cm²/g, 0.0589 cm²/g, 0.0529 cm²/g, HVL of 4.998 cm, 6.453 cm, 7.202 cm, and TVL of 16.603 cm, 21.437 cm, 23.926 cm, respectively. Test samples made from slag-based geopolymers have a better shielding capability compared to fly ash-based geopolymers due to having higher attenuation coefficients as well as lower HVL and TVL, thus requiring less material to absorb radiation of the same energy level. (author)