Influence of D-Sorbitol on the Properties of Binders to Immobilize Acid Nuclear Wastes

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Title: Influence of D-Sorbitol on the Properties of Binders to Immobilize Acid Nuclear Wastes

Author(s): M. Collepardi, G. Grossi, M. Pellizon Birelli, and G. Ventura

Publication: Special Publication

Volume: 239

Issue:

Appears on pages(s): 525-532

Keywords: blast furnace slag; fly ash; nuclear wastes; solidification/stabilization; sorbitol

Date: 10/1/2006

Abstract:
A combination of ground granulated blast furnace slag, fly ash and calcium hydroxide has been used to immobilize acid nuclear wastes in the form of a hardened system in the absence of any aggregate. An aqueous solution of NaOH (19 M) was used for two purposes: first, to neutralize the acid waste and to transform it in a very basic system (pH>13); second, to activate the hardening of the binder. Due to the liquid-solid ratio lower than 0.70, the fresh mixture is relatively stiff. Superplasticizers based on sulfonated naphthalene and melamine or acrylic polycarboxylate do not work to fluidify this system. D-Sorbitol as well as other alditols are very effective in terms of higher workability and lower workability loss of this cementitious system. Surprisingly this chemical admixture increases the compressive strength of this cementitious grout at both early and longer ages at a given waterbinder ratio. The properties of this cementitious system in the absence and in the presence of D-sorbitol as chemical admixture (0.2-0.5% by weight of binder) have been studied in the form of workability of the fresh mixture, early and later compressive strength, leachability by water and X-ray diffraction analysis of the hydrated products of the hardened system.