Development and Optimization Criteria of Cementitious Mortars Used for the Immobilization of ILW Radioactive Waste

Abstract The cementing process is the most widely adopted method of intermediate-level waste (ILW) conditioning, involving the use of cement mortars to waste incorporation. The main challenge in processing these mortars lies in achieving an optimal balance among their components. Accordingly, this study aims to investigate the essential criteria for developing prototype cement mortars suitable for immobilizing Intermediate Level Waste by investigating the effect of key parameters, such as water/cement and sand/cement ratios, on the workability of the compound. Different types of cement (CEM I, CEM II and CEM IV) were used, also analyzing the effect of aggregate particle size composition on workability, and the benefits of adding superplasticizer to reduce the water/cement ratio and ensure high mechanical strength were evaluated. It was observed that increasing the water/cement ratio enhanced workability, while increasing the sand/cement ratio decreased it. The use of superplasticizer decreased the water/cement ratio with the same workability. In addition, the grain size composition like that provided by Andreasen improved workability compared with the as-is composition. The investigation and the integrated multifactorial approach allow for a rapid convergence towards the production of a prototype mortar with the desired characteristics for the immobilization of Intermediate Level Waste.