NTU Singapore scientists have managed to address the shortage of sand in 3D printing by replacing the same with recycled glass waste.
According to the scientists, glass is made up of silica—a major component of sand—and can therefore be recycled into other products.
But while glass is 100% recyclable with no reduction in quality, it has for some odd reason remained one of the least recycled waste types.
The NTU team is hoping to change that and has now 3D printed a concrete bench by using a specially formulated concrete mix of recycled glass, commercial cement products, water, and additives.
According to the scientists, the 40cm tall L-shaped 3D printed structure has so far shown excellent buildability—the printed concrete does not deform or collapse before the concrete cures.
It has also displayed top notch extrudability, implying that the special concrete mix is fluid enough to flow through the hoses and print nozzle.
What makes the new material particularly interesting is that glass is naturally hydrophobic; less water is required to create a concrete mix suitable for 3D printing use and this makes it well suited for the said purpose.
To enable printing, the team led by professor Tan Ming Jen adjusted the control systems of the 3D printer to match the flow rate of the nozzle to the hardening properties of the concrete.
The printing was then carried out in a single build using a 4-axis gantry robotic printer which has a print volume of 1.2 metre x 1.2 metre x 1 metre.
Once ready, the specially designed concrete mixture was fed to a pump and transported to a nozzle mounted on the robotic arm, depositing the material layer by layer according to the digital blueprint.
Going forward, NTU will collaborate with Singapore start-up company Soda Lemon to 3D print larger scale and more diverse structures using the recycled glass concrete mix.
They also plan to optimize the current printing algorithm for consistent performance.
Image and content: NTU Singapore