High-Performance and Durable Green Geopolymer Based on Slag/Alumina Sludge Ash Incorporating CuFe₂O₄ Spinel Nanograins for Enhanced Gamma Radiation Shielding

Abstract This research aims to assess the effectiveness of incorporating thermally treated alumina sludge ash (ASA) as a partial replacement for slag-based geopolymer (SG-Geo) at various ratios (5%, 10%, and 20% by mass) and the integration of cost-efficient CuFe₂O₄ spinel nanograins (CF-NGs) at different addition levels (0%, 0.5%, 1%, and 1.5% by weight). The study focuses on enhancing the physico-mechanical features and durability of the geopolymer in aggressive environments, particularly against sulfate (SO₄2−) and chloride (Cl−) attacks. Key performance indicators include compressive capacity, and non-evaporable water content, to improve the ionizing radiation shielding properties of these eco-friendly geopolymer pastes to advance sustainability objectives. The fabricated samples were tested at 0.662 MeV, 1.17 MeV and 1.33 MeV photon energies as radiation shielding material to achieve sustainability goals. Gamma attenuation parameters (MAC, LAC, MFP, HVL and TVL) were determined experimentally and calculated theoretically using Phy-X/PSD software. The findings indicate that both theoretical and experimental results are consistent, with the radiation protection efficiency improving as ASA content increased up to 20%. The addition of 1.5% CF-NG notably enhanced the compressive strength at 28 days, as well as the gamma attenuation efficiency. Among the various SG-ASA hardened nanocomposites, Mix PS3CF1.5 exhibited superior physical and mechanical properties, along with the most effective gamma radiation shielding performance.