EURAD MAGIC project – Chemo-Mechanical AGIng of Cementitious materials under coupled disturbances based on a multi-scale approach

Introduction The long-term chemo-mechanical performance of the cementitious components of a radioactive wastes repository depends notably on the cement formulation as well as on the bio/geochemistry of the disposal environment and the interactions with other near-field materials.Despite the extensive R&D studies carried out in the last decades, the alteration processes in ce-mentitious material under complex coupled perturbation phenomena are still not fully explored and understood, especially the link between the chemical and the mechanical evolution. Moreover, recent innovations in terms of material formulations (low-pH cements notably) require dedicated R&D to better understand how their long-term mechanical performance is influenced by the host rock and the near field conditions (i.e., pore saturation, chemical evolution of the barriers, microbial impact and gas formation).Summary and objectivesThe MAGIC WP within the European Joint Program on Radioactive Waste Management (EURAD) is a project that will assess the impact of several simultaneous chemical processes (hydrolysis, multi-ionic attack (i.e. sulfate and magnesium, carbonation) on the mechanical properties of cementitious materials and their evolution. The WP proposes different processes to assess the long-term perfor-mance of cement based materials, including a hydraulic transient (re-saturation period with waters from different geological media). It will leverage and build on the advances on past and current Euro-pean projects (i.e. CEBAMA, PREDIS, ACED, DONUT WPs) and explicitly exclude repeating activi-ties already conducted in these previous or ongoing projects.The use of several cement formulations will help to compare their long-term performance under the same conditions. Another important aspect to be considered is the impact of microbial activity on the evolution of the chemo-mechanical properties of cementitious materials. The integration of innovative material characterization and modelling from nano to laboratory to full scale is a key issue of the pro-ject. The final goal is to obtain an improved understanding of mechanical ageing of cementitious materials exposed to various representative chemical disturbances coming from the disposal envi-ronment including 3 main objectives:• To quantify the mechanical multi-scale evolution of cementitious materials under the chemical degradation expected in repository environments, identifying the main reactive pathways at the repos-itory scale during the re-saturation phase and at the saturated conditions. • To obtain a reference chemo-mechanical model of Portland and low-pH concretes exposed to relevant disposal environments, considering representative boundary conditions. • To estimate the extent of the impact of microbial activity on concrete properties (low-pH and Portland cement) in partially and fully saturated media.The project started in June 2021 for a duration of 3 years