CEBAMA

The HORIZON 2020 EURATOM Collaborative Project “Cement-based materials, properties, evolution, barrier functions (Cebama)” was developed with the overall objective to support the implementation of geological disposal of radioactive wastes by improving the knowledge base for the Safety Case. Cement-based materials are highly relevant in this context, being used as waste forms, liners and structural components or sealing materials in different types of host rocks and disposal concepts. Specific objectives of Cebama were (i) experimental studies of interface processes between cement-based materials and repository host rocks or bentonite, and their specific impact on transport properties and processes, (ii) quantifying radionuclide retention under highly alkaline pH conditions typical of cement-based material, and (iii) developing comprehensive modelling approaches. The modelling studies supported interpretation of results and prediction of the long-term evolution of key transport characteristics such as porosity, permeability and diffusion parameters especially in the interface between cement-based materials and the engineered and natural barriers.

The aim of our investigations was to enhance the mechanistic understanding of the radionuclide uptake and retention in cementitious materials, and to evaluate the relevance of cement alteration processes on the solid speciation of radionuclides in aged concrete, combining experimental and computational approaches. A bottom-up approach was used to unravel contributions of individual cement hydration phases on the radionuclide retention behaviour of 226Ra and anionic radionuclide species of Mo, Se or I, in addition to studies on hardened cement pastes. Moreover, we contributed to a benchmark exercise on reactive transport modelling of long-term interactions between cementitious barriers and clay host rocks.