Recycled Glass Use In Concrete

By Author: Perry Riblet
Total Articles: 1
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The concrete industry is constantly interested in innovations, better performance and how to lower its carbon footprint. Amazingly, cement production accounts for about 5% of the total CO2 emitted in the atmosphere around the world.

CO2 Emissions

Another method to consider it is that each lot of cement produced outputs a lot of CO2. A lot of it comes from the high melting temperature (2500°F) and from the process of decarbonation of limestone. Thus to lower the carbon footprint, the industry would have to either change the cement production process or to use less cement in concrete mixtures. Much research has been done around the world in finding how to dispose of commercial byproducts such as fly ash or perhaps silica fume and use them in creating concrete. Thus a lot that these are now commonly found in most concrete mixtures. Exactly what other material can be recycled into cement?

Recycled glass

Meet recycled glass

In the US, just 33% of the glass products is being recycled and just 40% of the glass that is collected is recycled. Part of the reason can be that glass recycling is ...
... still costly due to transportation and color sorting. Crushed glass in large particles (larger than 75µm) produces an expansive solution that results in concrete cracking, thus the particle size must be finer than 75µm to certainly not create a great alkali silicate reaction. When this happens, mortar durability is increased. The only exception to this really is the use of large glass particles in creating concrete kitchen counter tops. These tend to be becoming very popular as they combine cost saving, green practices, beautiful and unique results.

A better solution is glass powder as it has been found to improve concrete's compressive strength as well as durability. Another great discovery was the water reducing effect of glass powder, leaving more water to improve the cement's workability.

Michigan State College has been conducting extensive research in their labs on the utilization of glass in concrete on their campus. They have managed to replace regarding 20 percent of the cement utilized to produce concrete by milled, or finely ground glass. The resulting concrete becomes lighter but has the exact same appearance with normal concrete, perhaps a little lighter in color. More research is underway to test all factors required to make this new element a standard in the industry. To read more on this, two papers were published on the durability of the mixture, one in the Journal of Solid Waste Technology and Management, and the other in the Journal of Construction and Building Materials of Michigan State College.

The American Log of Technology Research (AJER) conducted workability test, density test and compressive strength test on waste glass powder in concrete. They also found that glass powder does increase the workability, density and compressive strength of concrete. Read the full report here.

Europe and India have additionally effectively spearheaded research in this emerging field. The study conducted by Dr. G.Vijayakumar, Ms H. Vishaliny and Dr. D. Govindarajulu at Pondicherry Engineering College, in Pondicherry India, had the following very positive conclusions:

"Replacement of glass powder in cement by 20%, 30% and 40% increases:
the flexural strength by 83.07%, 99.07% as well as 100% respectively.
the compressive strength by 19.6%, 25.3% and 33.7% respectively.

Glass powder concrete increases the compressive, tensile as well as flexural strength effectively, when compared with conventional concrete. Very finely ground glass has been shown to be great filler." The complete report can be read here*

The Centre of Sustainable Development in Quebec, Canada was an early adopter of powder glass in concrete, which allowed them to reach a LEED Platinum certification. They simultaneously managed to reduce the amount of concrete used and the amount of glass dumped in landfills.

It remains too early to understand whether or not glass can be utilized for shotcrete applications. Definitely not enough testing as well as research has been done on wet or dry mix shotcrete. However, promising results were discovered in early findings for dry blend on rebound and reinforcement of bar encapsulation in the location phase.

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