Recycled glass to replace sand in 3D printable concrete

Concrete is a very popular building material, so much so that one of its key ingredients, sand, is becoming increasingly rare. Therefore, scientists are now investigating the possibility of replacing this sand with glass waste that would otherwise end up in landfills.

Although glass is considered a recyclable material, it is often not recycled.

In many cases, due to a lack of properly equipped recycling facilities, or the fact that waste glass often comes in the form of many fragments too small to be conveniently sorted by color, such sorting is a requirement for recycling.

Find a use for non-recycled glassresearchers at Nanyang Technological University, Singapore, considered use it as a substitute for sand often used in 3D printed concrete structures. After all, glass is made of silica, which is one of the main components of sand.

For their study, the scientists ground waste glass into five different shard sizes – coarse, medium, fine, superfine and “moon dust” – to replace the sand and gravel that normally serve as aggregate in concrete. . The crushed glass was combined with the other two ingredients of concrete, cement and water.

The mixture was then extruded through the nozzle of a 4-axis gantry robotic 3D printer, to create a 40cm high L-shaped concrete bench.

Once the concrete had cured, its strength was found to be similar to that of traditional sand-filled concrete.

Additionally, the researchers observed that the poured concrete did not warp or sag before it hardened, and was fluid enough to pass easily through the printer’s nozzle.

Also, since glass does not absorb as much water as sand, less water was needed to make the concrete.

Our research has shown that recycled glass can be used to replace up to 100% of sand in concrete for 3D printing. The result is a concrete bench whose mechanical strength meets acceptable industry standards. With sand being mined at a much faster rate than it can be replenished naturally, the prospect of using recycled glass in building and construction is becoming increasingly attractive.

Andrew Ting

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I remember a few years ago DB Brewery (New Zealand) started an initiative to protect their country’s beaches. They created a mechanism that turned empty beer bottles into sand to save their country’s beaches.

More information: www.sciencedirect.com (English text).

Going through www.ntu.edu.sg

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