Researchers at Australia's RMIT University and University of Melbourne have investigated the effectiveness of graphene oxide (GO) sheets in enhancing the compressive strength of 3D-printed cementitious mortar.
They added graphene oxide to the cement used as a binder in 3D-printed concrete. After experimenting with different amounts, it was found that when graphene oxide was added at a dosage of 0.015% the weight of the cement, the resulting concrete exhibited better inter-layer bonding. This boost produced a 10% increase in overall strength.
The team found that The addition of graphene oxide (GO) to cement-based composites improves their mechanical characteristics.
Two doses of GO were evaluated: GO-0.015 and GO-0.03 (GO-to-binder weight ratios). The inclusion of GO at both concentrations enhanced the compressive strength of the printed specimens under various loading directions, but the gain in strength was greater for GO-0.015 (10%) than for GO-0.03 (5%). They found that underfill in the GO-0.03 specimen produced significant voids between filaments, which undermined the benefits.
"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," said RMIT's Assoc. Prof. Jonathan Tran. "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."
As an added bonus, since graphene is highly electrically conductive, it's possible to pass an electrical current through the hardened concrete. It is hoped that this functionality could one day be utilized in a crack-detection system, wherein even the smallest of cracks would interrupt an electrical circuit running through a concrete structure.
More research still needs to be conducted on that front, plus the scientists have yet to determine how the strength of the augmented 3D-printed concrete compares to that of traditional cast concrete.
In previous studies, graphene oxide has been used to form a protective coating on concrete, and to increase the bonding strength of shredded face mask fibers which were used to strengthen concrete.