Cementation is one method to immobilize radioactive waste in order to protect the environment from radionuclide release. Rice husk ash (RHA) has been success used as pozzolanic materials for several years. The aim of this research is to understand the ability of RHA pozzolan on strontium waste cementation process. This research was conducted by mixing strontium liquid waste with sand, Portland cement and several composition of RHA. The cement blocks were tested by a pressing machine to determine their compressive strength after cured for 28 days. Strontium leaching rate encapsulated on the blocks was analyzed by Hitachi Zeeman 8000 Atomic Absorption Spectrophotometer for 21 days. The strontium adsorption process of RHA was also analyzed by X-ray Diffraction (XRD). This research showed that the compressive strength is affected by composition of RHA and waste loaded into the blocks, but it is not affected by water cement ratio on the cement blocks. Addition of RHA up to 10v/o increases the compressive strength of mortar, but the further addition is affected inversely. The decreasing of compressive strength is also caused by the increasing of sand content and strontium waste loaded. But, these values obtained in this research still meet IAEA standard. The ability of RHA to adsorb strontium that is affected by the flow rate of waste and initial concentration of strontium waste leads to the fulfilling of IAEA leaching rate standard for cementation and hence RHA could be used for strontium waste cementation.

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