Physical and adsorption characteristics of geopolymers prepared using 1–5 M NaOH solution for immobilization of radioactive wastes

The temporal variations of compressive strength and flowability (slump-flow), and the adsorption behaviors of Co, Sr, and Cs for fly ash-based geopolymers, were investigated for immobilization of radioactive wastes. The geopolymer samples were prepared by using 1–5 M NaOH solution and cured at ambient temperature. The strength and flow were related to the amount and concentration of NaOH solution. The trends were discussed with the amount of heat generated at an early stage of curation. In addition, the geopolymers adsorbed Co equivalent to cements, Sr and Cs more than cements. The trends of absorption were related to the pH of leachates and the magnitude of x-ray diffraction (XRD) peaks of materials which possess larger distribution coefficients. We considered the possibilities to improve performance and to resolve problems in workability for actual use for immobilization of radioactive wastes according to the results of the present work.