Properties of Tungsten Mine Waste Geopolymeric Binder- Introduction I

This is the first part introduction of properties of tungsten mine waste geopolymeric binder.

Studies of alkali-activated cements have a long history in the former Soviet Union, Scandinavia, and Eastern Europe. In 1978, Davidovits created the term ‘‘geopolymer’’, to characterise new materials with the ability to transform, polycondense and adopt a shape rapidly at low temperatures like ‘‘polymers’’. The polymerisation process involves a chemical reaction under highly alkaline conditions on Al–Si minerals yielding polymeric Si–O–Al–O bonds with empirical formula Mn [–(Si–O2)z–Al–O]n. wH2O, where n is the degree of polymerization, z is 1, 2 or 3, and M is an alkali cation, such as potassium or sodium. Davidovits reported several advantages of geopolymeric cementitious systems over Portland cement mainly environmental, due to the fact that geopolymeric based concrete has a much longer service life than Portland cement based ones, to the metals waste encapsulation capacity and to lower CO2 emissions. The geopolymerization requires a precursor that contains significant quantities of silicon and aluminium held in an amorphous phase such as ashes from power stations or mining and quarrying wastes.

Over the last years several authors have reported research in a large number of aspects related to geopolymeric based binders such as: dependence of the nature on source materials (geopolymers synthesised from calcined sources show a higher compressive strength than from raw materials), immobilization of toxic metals, reaction mechanisms and hydration products, the role of calcium in geopolymerization, manufacture operations and even the development of lightweight building materials.

 

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