2025 Volume 24 Issue 2 Pages 44-51
Some low-level radioactive wastes categorized as shallow underground pit disposal may contain high concentrations of sulfate. There is concern that sulfate may interact with cementitious materials and affect the physical properties of the waste. We examined the interaction of sulfate-containing cementitious materials by using drums of the same size as actual waste bodies. Two specimens with different sulfate concentrations were prepared and their chemical and physical properties were analyzed. Results showed that different sulfate concentrations affected the temperature history and phase composition within the waste, and the sulfate concentration also changed the composition of the products. It was observed that sulfate accelerated the rate of the hydration reaction of the cement paste, which may have resulted in a greater temperature increase. It was also shown that sulfate affects the amount of calcium silicate hydrate (C-S-H) produced. In specimens with high sulfate concentrations, the amount of C-S-H formed decreased, as did the reaction rate of the slag. This could be a result of sulfate interfering with the hydration reaction of the slag.
