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Glass can be turned into micron-sized fibers. These fibers are also known as milled glass. These milled glass fibers have been used for decades within the construction industry to insulate the walls and roofs of houses. Nowadays, the construction industry has found a new use for milled glass as a composite material in the recycled aggregate, and high-performance, concretes.
What is Milled Glass?
Glass can be milled to create micron-sized fibers, with the most common usage being fiberglass. Fiberglass consists of a number of these ultrafine fibers mixed with a polymer. These individual glass fibers have properties similar to polymers and carbon fiber, although they are not as strong or rigid as carbon fiber. However, milled fiberglass is much cheaper to produce and create a less brittle structure when used in a composite material.
The properties of fiberglass lend themselves to strength applications, whilst creating a more lightweight and stable material than the pre-composite material. Milled glass is also known to have high thermal insulation properties. Glass fibers are created from the extrusion of silica-based compounds (or other formulation glasses), where they are heated and drawn into fine fibers with very small diameters.
Milled Glass in Concrete
Milled glass has been used in glass wool to insulate lofts and walls for many decades. However, the biggest breakthrough use of milled glass in the construction industry has come in its incorporation into concrete in various forms.
Recycled Aggregate Concrete
Waste milled glass has found use within the construction industry – it can now be recycled into concrete materials, to create recycled aggregate concretes. The concretes in question are a specific type that incorporates colored waste glass found in landfills and aggregate rock, so these new developments help the environment by recycling multiple waste materials. The waste glass is milled and used as a partial replacement for cement in conventional aggregate concretes. Researchers have made multiple composites that vary by the amount of fiberglass incorporated.
In these concretes, the waste glass is milled into micron size fibers which then undergo a pozzolanic reaction with the hydrate moieties in the cement. This reaction forms a secondary calcium silicate hydrate (C-S-H).
The incorporation of fiberglass brings many beneficial properties to concrete. The result is not only concrete that is more environmentally (and waste) friendly, but the incorporation of these fibers creates a high-performance cement.
These high-performance concretes can be used in the construction of buildings and replace steel. They have the same compressive strength as many common building materials, such as steel, but the recycled parts mean that the cost of these concretes are about half the price of conventional materials. They also have high durability, high resistance to crushing and high flexural strength.
Freeze-Thaw Resistant Concrete
Waste milled glass has also been used to create specific recycled concretes that possess high resistance to freeze-thaw processes, something which is known to be a cause of major structural failure in many environments around the world. A material that can withstand such natural processes is of great benefit to the construction industry.
These concretes, much like the others, have added milled glass in lieu of some of the cement. These concretes have an improved freeze-thaw resistance and a resistance to surface scaling of concrete compared to conventional concrete building materials. Like many of the recycled concretes, the freeze-thaw resistant concretes also have a higher strength, higher compressive strength and enhanced durability to natural environments.
Sources:
- Fibre Glast: https://www.fibreglast.com/product/132_inch_Milled_Glass_Fibers_38/Fillers
- AzoBuild: https://www.azobuild.com/news.aspx?newsID=22873
- US EPA: https://cfpub.epa.gov/ncer_abstracts/index.cfm/fuseaction/display.highlight/abstract/9507
- “Strength and durability of recycled aggregate concrete containing milled glass as a partial replacement for cement”- Nassar R-U-D., et al, Construction and Building Materials¸ 2012, DOI: 10.1016/j.conbuildmat.2011.10.061
- “The Feasibility of Using Milled Glass Wastes in Concrete to Resist Freezing-Thawing Action”- Abendeh R., et al, International Journal of Civil, Environmental, Structural, Construction, and Architectural Engineering, 2015
- “Compressive Strength of Concrete Containing Milled Glass as Partial Substitute for Cement”- Raheem S. B., et al, International Journal of Advanced Engineering, Management and Science (IJAEMS), 2017, DOI: 10.24001/ijaems.3.4.3
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