title: Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: leaching behaviour of the solidified waste form, mechanisms of zinc retention.
abstract: To assess the potential of calcium sulfoaluminate cement to solidify and stabilize wastes containing high amounts of soluble zinc chloride (a strong inhibitor of Portland cement hydration), a simulated cemented waste form was submitted to leaching by pure water at a fixed pH of 7 for three months, according to a test designed to understand the degradation processes of cement pastes. Leaching was controlled by diffusion. The zinc concentration in the leachates always remained below the detection limit (2 μmol/L), showing the excellent confining properties of the cement matrix. At the end of the experiment, the solid sample exhibited three zones which were accurately characterized: (i) a highly porous and friable surface layer, (ii) a less porous intermediate zone in which several precipitation and dissolution fronts occurred, and (iii) the sound core. Ettringite was a good tracer for degradation. The good retention of zinc by the cement matrix was mainly attributed to the precipitation of a hydrated and well crystallized phase with platelet morphology (which may belong to the layered double hydroxide family) at early age (≤ 1 day), and to chemisorption onto aluminum hydroxide at later age.
authors: Commissariat à l'Energie Atomique et aux Energies Alternatives, CEA/DEN/MAR/DTCD/SPDE, BP17171, 30207 Bagnols-sur-Cèze cedex, France.
authors: Stéphane
authors: S
authors: Berger
authors: Céline
authors: C
authors: Cau Dit Coumes
authors: Jean-Baptiste
authors: JB
authors: Champenois
authors: Thierry
authors: T
authors: Douillard
authors: Patrick
authors: P
authors: Le Bescop
authors: Georges
authors: G
authors: Aouad
authors: Denis
authors: D
authors: Damidot
mesh_terms: D017607:Aluminum Compounds / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D003252:Construction Materials; D006863:Hydrogen-Ion Concentration; D013457:Sulfur Compounds / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*; D017967:Zinc Compounds / Q000737:chemistry*
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D002712:Chlorides; D013457:Sulfur Compounds; D017967:Zinc Compounds; C529583:calcium sulfoaluminate; C016837:zinc chloride; D015032:Zinc