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Graphene oxide study paves the way for smart concrete

Graphene oxide study paves the way for smart concrete

Engineers from RMIT University and the University of Melbourne have enhanced 3D printed concrete by incorporating graphene oxide into the cement mixture, opening the door to the potential development of ‘smart’ walls capable of monitoring cracks.

The research revealed that the addition of graphene oxide, a nanomaterial commonly used in batteries and electronic gadgets, imparted electrical conductivity to concrete and increased its strength by up to 10 per cent.

Jonathan Tran, research supervisor and associate professor at RMIT’s School of Engineering, said this concrete had the potential to create ‘smart’ buildings where walls can act as sensors to detect and monitor small cracks.

While current detection methods, such as ultrasonic or acoustic sensors, are non-destructive and widely used in the construction industry to detect large cracks in concrete structures, the early detection of smaller cracks remains a challenge.

“The equipment for these methods is often bulky, making it difficult to regularly use for monitoring very large structures like bridges or tall buildings,” said Tran.

“But 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.”

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While the research was preliminary, Tran said graphene oxide had the exciting potential to make 3D printed concrete more viable in the construction industry, which could have positive impacts on cost and sustainability.

“Current concrete structures are created using formwork, which is where you create a mould before pouring fresh concrete mixture into it,” he said. “Formwork requires a lot of labour, time and money, and it often creates a lot of waste.”

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

Due to its layer-by-layer printing process, 3D printed concrete can potentially result in weaker bonds between each layer. However, the introduction of graphene oxide into the concrete enhances its extrudability, facilitating better inter-layer bonding and thereby maximising overall strength.

“Graphene oxide has functional groups on its surface, which are like sticky spots on the surface of a material that can grab onto other things,” Tran said. “These ‘sticky spots’ are mainly made of various functional groups containing oxygen, which play a crucial role in facilitating its stronger bonds with other materials like cement.”

“This strong bonding can improve the overall strength of the concrete.

“However, more research is needed to test if concrete with graphene oxide can match or surpass the strength of traditionally cast concrete.”

Too much of a good thing 

Lead researcher, RMIT PhD candidate Junli Liu, said the strength of the concrete could be increased if the bond between graphene oxide and the concrete mixture was improved.

The research tested two dosages of graphene oxide in cement and found the lower dosage (0.015 per cent of the weight of cement) was stronger than the higher dosage (0.03 per cent of the weight of cement).

Tran said adding too much graphene oxide could impact the strength and workability of the concrete mix, which can cause potential issues with printability, strength and durability. “Concrete is a carefully balanced mixture,” he explained. “Adding too much graphene oxide can disrupt this balance, particularly the hydration process, which is crucial for concrete strength.”

“Too much graphene oxide can impact the flow of concrete, making it harder to extrude and therefore creating a structure with more gaps between layers of concrete.

“Graphene oxide can also clump together instead of spreading out evenly, which can create weak spots in the concrete and reduce its overall strength.”

The next phase of the research involves investigating the electrical conductivity of graphene oxide in concrete to test its viability as a potential smart material.

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