Garbage sorting has become more and more popular in our lives, and many people will pay attention to its recycling category when discarding items. If there is discarded glass, what category does it belong to?
Waste glass is recyclables can be said to be "sending sub-topics", but what few people know is that the recovery rate of this recyclable is not high. In Singapore, for example, only 13% of the 74,000 tonnes of glass waste generated in 2021 will be recycled, so where does the remaining glass go?
▲ Image from: NTU
The recycling process is complex and costly, can not be incinerated, and it is difficult to degrade in landfills, and waste glass can be said to be the "oldest difficulty" in municipal garbage. But a team of researchers at Nanyang Technological University (NTU) in Singapore has found its hangout – waste glass, which is difficult to recycle, can be used as a substitute for sand in 3D printed concrete.
▲ Image from: NTU
Concrete is a building material that everyone is familiar with, and there is an indispensable material - sand, which needs to be used to adjust the proportion and optimize the mix ratio of various materials. The reason for choosing glass instead of sand is also simple: glass is made of silica, which in turn is the main component of sand.
▲ Image from: Unsplash
The researchers crushed the glass waste into five different sizes of debris: coarse, medium, fine, ultra-fine and moondust, which was used to replace sand and gravel, which are typically used as concrete aggregates. Because to save cement and increase concrete strength, different sizes of particles are required to minimize the void between sand particles.
▲ Image from: NTU
Using this "special recipe" mixture of recycled glass, the researchers successfully created a 40 cm tall concrete object with a 3D printer. The poured concrete does not deform or collapse before curing, and the fluidity can easily flow through the printer nozzle.
▲ Image from: NTU
What's more, the strength of this "special" concrete after curing is similar to that of traditional sandy concrete.
It is worth mentioning that in addition to 3D printed concrete, a research team at Deakin University in Australia also used glass waste instead of sand to create glass-based polymer concrete with non-3D printed structures.
Glass-based polymer concrete at Deakin University, image courtesy of Deakin University
All of this is enough to show that whether it is 3D printing or using traditional methods, it is possible to replace sand with glass waste to make concrete, and the proportion of substitution can even reach 100%.
Using discarded glass instead of sand to make concrete is for glass, but also for sand. The development of cities means that the demand for building materials has increased greatly, and river sand is often used in the construction of concrete, which has led to the amount of sand being mined far from meeting the increasing demand.
▲ Image from: NTU
The use of glass waste instead of sand to make concrete will not only make so many waste glass that has nowhere to be placed, but also slightly overcome the "sand dilemma" faced by the current manufacturing of concrete, which undoubtedly has broad prospects.
In fact, there is an unexpected benefit to this, because glass is not as absorbent as sand, so it requires less water to make concrete in this way.
People always say that "garbage is a misplaced resource", and this is exactly what waste glass does, and when it is put from the garbage heap into the concrete, it becomes a building material. It uses both waste and resources, and it can be said that it is a lot of success.