Researchers from Nanyang Technological University, Singapore (NTU Singapore) has developped technology that uses recycled glass in 3D printing, opening the doors to a more environmentally sustainable way of building and building.
Glass is a material that can be 100% recycled without loss of quality, yet it is one of the least recycled types of waste. At the same time, population growth, urbanization and infrastructure development have led to a shortage of sand, with climatologists calling it one of the biggest sustainability challenges of the 21st century.
For these reasons, the NTU research team is looking to find ways to recycle glass by 3D printing it into everyday objects. One of their innovations published recently in the Journal of Building Engineering used a specially formulated concrete mix including recycled glass, commercial cement products, water and additives to 3D print a concrete bench.
Determining the optimal concrete formulation, the NTU research team managed to 3D print a 40cm high L-shaped bench as a proof of concept that their material could be 3D printed into a structural product (bearing of weight) every day. In lab compression tests and filament quality (strength) tests, the 3D printed structure showed excellent buildability – the printed concrete does not warp or collapse before the concrete does. hardens – and extrudability, which means that the special concrete mix is fluid enough to flow through the pipes and printing nozzle.
A new way to recycle glass
The study’s lead researcher, Professor Tan Ming Jen of the NTU School of Mechanical and Aerospace Engineering (MAE), said the team had come up with a workable formula, demonstrating for the first time that glass can actually be used. to 3D print a bench. with excellent structural integrity.
Following the successful proof of concept, the NTU research team believe their development offers a new route to recycling waste glass and can contribute to a greener building and construction industry for Singapore and beyond. of the. The new development builds on previous 3D printing for construction research by Professor Tan and his team at NTU’s Singapore 3D Printing Center (SC3DP).
The NTU scientist was also behind the 3D printed bathroom project in 2019, where an unfurnished bathroom was printed in 12 hours in Singapore, half the time it takes to conventionally build the bathroom. same setup. The latest innovation is an example of groundbreaking research that supports the NTU 2025 strategic plan, which aims to address humanity’s grand sustainability challenges and accelerate the translation of research discoveries into innovations that mitigate human impact on the environment.
Replacement of sand in concrete
Sand is a vital component of concrete, ensuring its durability. Reports from the United Nations Environment Program have also revealed that around the world, aggressive sand mining from rivers has led to pollution, flooding and other environmental consequences.
The first author of the NTU-led study, Andrew Ting, a researcher at SC3DP, said the research has shown that recycled glass can be used to replace up to 100% of the sand in concrete for 3D printing. The result is a concrete bench whose mechanical strength meets acceptable industrial standards. The team believes their solution has great potential to alleviate the demand for sand in this sector in the future.
Also, because glass is a naturally hydrophobic material, less water is needed to create a concrete mix suitable for 3D printing.
How the L-shaped bench is 3D printed
Through detailed and extensive analysis and testing, the NTU research team established the optimal parameters for the recycled glass concrete mix that would allow it to be 3D printed. The components of the mixture include recycled glass ground into different size classes (medium, fine and superfine), commercial cement products, water and other additives.
To enable printing, the team adjusted the 3D printer’s control systems to match the nozzle output to the hardening properties of the concrete. Printing was then done in one go using a 4-axis gantry robotic printer which has a print volume of 1.2 meters x 1.2 meters x 1 meter.
The specially designed concrete mix 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 plan. The technology and know-how employed in this research project is protected by a Technology Disclosure filed through NTU’s Corporate and Innovation Society, which is also owned by the university.
In the future, the NTU research team, in collaboration with a Singaporean start-up, will examine 3D printing on a larger scale and more diverse structures using the mixture of recycled glass concrete, and optimize the algorithm. printing for consistent performance.