Long-term performance of cementitious materials used in nuclear waste disposal-a case study at SCK•CEN

This paper presents an overview of a research program at the Belgian Nuclear Research Centre (SCK•CEN) concerning long-termdurability of cementitious materials.The need for this research originates from the Belgian nuclear waste disposal concept, which proposes ordinary portland cement as the candidate binder for engineered barriers. Three main degradation mechanisms are considered: calcium leaching, carbonation and combined leaching/carbonation. Specifically, the effect of these mechanisms on microstructural changes and hence on physical and transport properties are discussed.The discussion concerns recent advances in experimental techniques and numerical tools in support of experimental programme. Novel experimental techniques cover accelerated degradation experiments for sound/fractured material, and transport experiments to determine water permeability and diffusion coefficient. Numerical tool covers recent implementation of lattice-Boltzmann based reactive transport code to handle micro-meso-continuum scale modelling.