The International Information Center for Geotechnical Engineers

Vitrification

Background

Amorphous materials usually have a glass transition temperature, below which the material behaves like glass. (Figure.1) Crystals is able to behave like glass under rapidly cooling too. If the cooling process takes place in a short time, molecules are not able to form crystalline structures. Instead, they remain in disordered structures as in liquids, forming glassy materials.

 

Figure.1 Illustration of Vitrification (Penn State University)

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At molecular scale, take water as an example, when water freezes, water molecules form covalent bonds and hydrogen bonds, forming ice crystals. However, if glass-forming additives were added, they can prevent water molecules from forming ordered crystal structures. As the temperature decreases, the velocities of water molecules are reduced. When the motion of molecules stops, they remain disordered, which is called a “glass”. The difference between frozen and vitrified liquid can be visualized in Figure.2. Glass has high strength and is chemically stable. The strength of the vitrified product can be 5 to 10 times of that for unreinforced concrete in both tension and compression. From stoichiometric point of view, vitrified products can absorb into their structure varying concentrations of a wide variety of different foreign elements. These advantages make soil vitrification effective in waste treatment.  


Figure.2 Difference between Frozen and Vitrification (University of Southern Mississippi)

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