Various additives for improving the performances of solidified forms of radioactive wastes by cementation technology: Recent advances and perspectives

The additives are crucial for improving the performance of the solidified forms of radioactive wastes by cementation technology. This paper reviewed the recent research advances in improving the cement and waste solidification performances using various additives, including the traditional pozzolanic active substances, biochar, fibers, nanomaterials and water reducer. The enhanced effect of various additives on the compressive strength, flexural strength, and nuclide leaching resistance, which belong to the performance requirements of the radioactive waste cement solidified forms, was summarized and analyzed. Silica fume, slag and fly ash can provide higher compressive strength, while zeolite, metakaolin, bentonite and activated carbon can reduce nuclide leaching. Fibers can significantly increase the flexural strength. Nanomaterials can provide superior mechanical properties, but currently there is little research and application in the waste cementation field. The water reducer can provide the necessary fluidity for the above multiple cement-based mixed materials. This review will deepen the understanding of solidification of radioactive waste and provide references for specific cementation formulations.