How Can Nanocellulose Contribute to Enhance the Performance of Concrete 3D Printing?

Concrete 3D Printing (C3DP), an emerging construction technique using extrusion, promises shorter construction periods, reduced waste, and CO2 emissions, and fosters more ecologically friendly construction practices. However, from a materials perspective, C3DP presents several challenges, particularly in balancing workability and rigidification, which significantly affect its mechanical performance. Enhancement in print material buildup can be achieved using viscosity-enhancing admixtures or fillers. At the nanoscale, cellulose nanocrystals (CNC) and cellulose nanofibers (CNF) have recently been used to improve the rheology, mechanical performance, and durability of concrete.
In this study, various cement pastes mixtures were formulated, incorporating two different types of gel suspensions of CNMs at dosages of 0.03%, 0.065%, and 0.20% by mass of cement. The CNMs used included two gel suspensions of CNC and CNF at dosages of 6.43% and 3.0% (by mass), respectively, in water. The visco-elastoplastic properties and stability of the investigated mixtures were evaluated in the fresh state. Moreover, the mechanical performance of the paste mixtures was assessed through flexural and compressive strength testing. The results demonstrated a beneficial effect of applying these CNMs in concrete for 3D printing, improving printability and build-up properties, while ensuring the targeted structural performance of a C3D printed object.