When glass is recycled, it is cleaned, sterilized, dried, sorted by color, and reduced to sizes that can range from pebbles to sand and even powder. This is known as “cullet” in the glass industry.
USES FOR GLASS CULLET
• Glass container manufacturing
• Fiberglass manufacturing
• Abrasives (sandblast media, etc.)
• Flux / binder in ceramics and bricks
• Soil amendment (an alternative to natural clays and zeolites, fly ash – calcium silicate hydrate)
• Filtration medium (swimming pools, and potentially municipal water)
• Frictionator in matches and ammunition
• Additive and flux in metal foundry
• Filler in paint and plastic
• Hydroponic rooting medium
CHARACTERISTICS OF GLASS CULLET
Density: | 2500 kgm3 | This is somewhat lower than most rock types, which are generally in the range of 2600-2850 kgm3 |
Hardness: | 5.5 – 6.5 on the Mohs Scale | Compare to quartz at 7 |
Fracture Characteristic: | Conchoidal | Particles are sub-angular (all angles less than 90 degrees), similar to that produced by flint |
Surface texture: | Highly smooth | Difficult for organisms to attach to the surface, providing an advantage in water treatment applications |
Melting point: | 2250 – 2350 degrees Fahrenheit | Compare to virgin materials, which melt at 2600-2900 degrees Fahrenheit |