Chemical and mineralogical characterizations of a low-pH cementitious material designed for the disposal cell of the high-level radioactive waste (HLW)
Résumé
This paper presents the chemical and mineralogical characterizations of a cementitious material and its
behaviour to temperature increase in conditions close to those of radioactive waste storage. The formulation,
based on a CEM III/C, silica fume, bentonite and hydrotalcite makes a low-pH cementitious grout with a low
viscosity. Results show that the mineralogical composition of this material evolves during setting. Two years after
setting, it is a macro porous geomaterial, composed of few C-(A)-S-H with a low C/S ratio (<0.4) formed from the
blast furnace slags. It also contains well-crystallized ettringite, hydrotalcite, calcite and still non hydrated C2S. In
contact with air, a substantial enrichment in calcite and gypsum is observed. The heating up to 90 ◦C leads to the
transformation of the Na-rich smectite of the bentonite into a Ca and/or Mg-rich one and the formation of opal-
CT, vaterite and aragonite. Hydrotalcite is stable whereas gypsum and anhydrite disappear