Non-thermal processes

• Cementation — the process of solidifying a liquid, sludge, solid, thermal residue, granular waste form, or calcine in cement matrix of crystalline calcium silicates, aluminates, and ferrate.

• Geopolymerization — the process of solidifying a liquid, sludge, solid, thermal residue, granular waste form, or calcine in an amorphous sodium aluminosilicate matrix.

• Bituminization — the process of solidifying a liquid, sludge, solid, thermal residue, granular waste form, calcine in bitumen.

• Forming — mixing a waste with cementitious, geopolymeric, bituminous, hydroceramic, or Ceramicrete-type additives and mixing in a form, i. e. can, vault, canister, and allowing the material to set or age.

• Pouring — similar to forming but the waste/additive mixture can be poured, extruded, or emptied into a form to set or age.

• Compositing — using metals, glass, cements, geopolymers, etc, to encap­sulate a waste that has already been solidified for special reasons such

RAW conditioning, immobilization and encapsulation 185

as heat dissipation, control of respirable fines in calcined or granular waste forms, and/or compressive strength requirements.

Often processes are coupled. For example, in France and the UK waste is calcined to remove excess nitrates before vitrification into a final waste form. This allows free-flowing oxides to enter the melter without nitrates being off-gassed or causing the particles to adhere to one another. Organic bearing wastes are often pyrolyzed to remove organics, if needed, before vitrification [14, 15].

Calcining is often performed before HIP, CIP, HUP, or CUP processes are performed, so that volatile species are not given off during the hot pressing or during the subsequent sintering. This ensures that the pressed waste form retains its integrity and form and does not crack during process­ing from off-gassing of hydrated or nitrated species.

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