Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Leaching behaviour of the solidified waste form, mechanisms of zinc retention

Sébastien Berger , C. Cau Dit Coumes (1) , J.-B. Champenois , Thierry Douillard (2, 3) , P. Le Bescop (4) , G. Aouad (5) , D. Damidot

1 CEA - CEA VALRHO
2 MATEIS - Matériaux, ingénierie et science [Villeurbanne]
3 CLYM - Consortium Lyon Saint-Etienne de Microscopie
4 LECBA - Laboratoire d'Etude du Comportement des Bétons et des Argiles
5 CERI MP - IMT Nord Europe - Centre for Materials and Processes

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 (2μmol/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. © 2011 Elsevier B.V.

Mots clés: diffusion; ester; experimental study; hydration; hydroxide; leachate; pH; retention; tracer; concentration (parameters); solidification; precipitation; surface property; waste management; building material; chemistry; Aluminum Compounds; Calcium Compounds; Chlorides; Construction Materials; Hydrogen-Ion Concentration; Sulfur Compounds; Zinc Compounds; aluminum hydroxide; inorganic compound; cement; Degradation process; Detection limits; Early age; Ettringites; Intermediate zone; Layered double hydroxides; Leachates; Platelet morphology; Pure water; Solid samples; Solidified waste forms; Surface layers; Three zones; Waste forms; Zinc concentration; Chemisorption; Chlorine compounds; Ion beams; unclassified drug; Portland cement; zinc chloride; aluminum derivative; Cement matrix; Cement paste; Cement hydration; calcium sulfoaluminate cement; calcium derivative; sulfur derivative; article; chloride; stabilization; calcium sulfoaluminate; waste treatment; dissolution; leaching; zinc; zinc derivative; aluminum compound; calcium; concentration (composition); crystallization; degradation; detection method

Domaines: Matériaux

Sébastien Berger, C. Cau Dit Coumes, J.-B. Champenois, Thierry Douillard, P. Le Bescop, et al.. Stabilization of ZnCl2-containing wastes using calcium sulfoaluminate cement: Leaching behaviour of the solidified waste form, mechanisms of zinc retention. Journal of Hazardous Materials, 2011, 194, pp.268-276. ⟨10.1016/j.jhazmat.2011.07.102⟩. ⟨hal-01813682⟩