Development of low-pH cementitious materials based on CAC for HLW repositories: Long-term hydration and resistance against groundwater aggression

One of the most accepted engineering construction concepts of underground repositories for high level waste considers the use of low pH cementitious materials. This research is focused on the development of those based on Calcium Aluminate Cements (CAC) with high mineral admixture contents that significantly modify their microstructural properties. Once their short-term hydration is known, this paper deals with the modifications generated in the pore solutions and in the solid phases of low-pH cement pastes based on CAC after 2 years of hydration, observing a high stability of the solid phases formed in the short-term. This paper also deals with the resistance of these materials to long term groundwater aggression using two types of aggressive agents: deionised water and groundwater from the real site of Äspö. Leaching tests show a good resistance of low-pH concretes against groundwater aggression but dependent on the leaching agent and on the concrete composition.