Research teases future of ‘smart’ 3D printed concrete walls

by Helena Morgan
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Preliminary research from RMIT University and the University of Melbourne has revealed that adding graphene oxide into cement mixture makes it possible to produce 3D printed concrete capable of becoming ‘smart’ walls that can detect cracks. 

Alongside cement, the researchers added graphene oxide – a nanomaterial found in batteries and electronic gadgets  – to a compound for 3D printed concrete. This particular pairing gave the concrete electrical conductivity and increased its strength by up to 10 percent. 

Ease of detection 

The graphene oxide infused concrete can potentially be used to build ‘smart’ sensor walls that are able to register cracks, according to RMIT associate professor Dr Jonathan Tran. One day, there may be buildings full of ‘smart’ walls. 

At present, non-destructive ultrasonic or acoustic sensors are used to detect large cracks in concrete structures; however, finding small cracks proactively remains difficult. 

Tran says these sensors are also bulky and cumbersome, which makes monitoring large structures such as bridges or buildings a challenge. So the researchers are understandably excited by the prospect of graphene oxide.

“The addition of graphene oxide creates the possibility of an electrical circuit in concrete structures, which could help detect structural issues, changes in temperature and other environmental factors,” he says. 

A time-and cost-saving solution 

The initial success of graphene oxide as a strength enhancer points to a future where 3D printed concrete is heralded as a cost-effective and sustainable asset in the construction industry.

Tran outlines how current concrete structures are made by making a mould and pouring fresh concrete mixture in – a process known as ‘formwork’ that creates unnecessary waste and is generally counterproductive. 

“Not only does 3D printed concrete help save time, money and labour, but you can also create more complex structures and reuse some construction waste in cement-based materials,” he says.

Graphene oxide’s ‘sticky spots’

Currently, 3D printed concrete’s reliance on layer-by-layer printing risks weaker bonds forming between each layer, but adding graphene oxide into concrete results in ease of extrusion, stronger interlayer bonding and overall greater material resilience. 

Tran likens the ‘functional groups’ on graphene oxide’s surface to ‘sticky spots’ that can grab onto other elements.

“These ‘sticky spots’ are mainly made of various functional groups containing oxygen, which play a crucial role in facilitating stronger bonds with other materials like cement. This strong bonding can improve the overall strength of the concrete,” explains Tran. 

He warns against premature celebration of graphene oxide as a substitute to concrete, however, as greater research is needed on the material’s ability to match or exceed the strength of traditionally cast concrete.

Getting the balance right

Lead researcher and RMIT PhD candidate Junli Liu suggests that the concrete could be further strengthened by refining the bond between graphene oxide and the concrete mixture. Getting the correct balance, however, is vital. 

“Concrete is a carefully balanced mixture. Adding too much graphene oxide can disrupt this balance, particularly the hydration process, which is crucial for concrete strength,” explains Tran.

The research sampled two doses of graphene oxide in cement and discovered the lower dosage – containing 0.015 percent of the weight of the cement – was stronger than the higher dosage of 0.03 percent of the weight of cement. 

An overdose of graphene oxide into cement also risks prohibiting extrusion and creating a structure with gaps between the layers of concrete. “Graphene oxide can also clump together instead of spreading out evenly, creating weak spots and reducing its overall strength,” warns Tran. 

Lead image: RMIT students Thanh Ha Nguyen, Wen Si, Junli Liu, Kien Nguyen and Shuai Li with a 3D printed concrete structure.

Photography supplied by RMIT.

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