In this study, cementitious wasteforms were fabricated to stabilize and solidify dispersible ¹⁴C-bearing SrCO3. Ordinary 

Portland cement was blended with SrCO3 at contents of 20–60 wt% and cured for 7 and 28 days under sealed and open 

curing conditions. Mechanical integrity was evaluated by uniaxial compressive strength, while phase evolution and microstructural

development were characterized depending on the SrCO3 loading. Chemical durability was assessed by the 

ANSI/ANS-16.1 standard method, with carbon and strontium releases quantified. The compressive strength results showed 

that sealed curing which maintained continuous cement hydration with homogeneous water retention in the wasteform 

led to 14–40% higher compressive strength than open curing after 28 days. The microstructural, crystallographic, and 

thermal analyses revealed that the decrease in compressive strength as waste loading increase was related to the evolution

of phases and changes in microstructural void structure. It was confirmed that SrCO3 acts as a chemically inert filler 

and it is physically embedded within the hydrated C-S-H matrix. Leaching tests showed that Sr leaching was effectively 

suppressed, whereas carbon leaching appeared higher due to the mobility of carbonate species in alkaline cementitious 

systems. Based on the Sr and carbon measurements, upper and lower bounds for 14C leaching are proposed to provide a 

conservative framework for the safety assessment of 14C-bearing cementitious wasteforms.