Effect of graphene oxide on physical and mechanical properties of 3D printed concrete

Graphene oxide (GO), as a novel nanomaterial, can effectively improve the properties of 3D printed concrete. However, the optimization mechanism of the dosage control on the physical and mechanical properties of the material still requires systematic research. In this study, through fluidity tests, axial compression tests, porosity tests, and scanning electron microscopy (SEM), the effects of a gradient GO dosage on the fluidity, compressive strength, and microstructure of 3D printed concrete were evaluated. The findings indicate that: (1) The fluidity of the 3D printed concrete increases with increasing GO content. Notably, the concrete with more than 0.4 weight percent (wt.%) GO falls below the process standard for 3D printed technology. (2) For the cast-in-place group, when the GO content is 0.1, 0.2, and 0.3 wt.%, the compressive strength increases by approximately 4%, 7.3%, and 16.8%, respectively, compared to concrete without GO, reaching values of 42.8, 44, and 47.9 MPa. The compressive strength of the 3D printed group also shows an increase of 0.2%, 4.9%, and 9.9%, resulting in values of 48.5, 48.6, 50.9, and 53.3 MPa, respectively. (3) The incorporation of GO into concrete causes a porosity reduction of 2.22% to 4.03%, respectively, accompanied by a decrease of approximately 7000 gel pores and a reduction in the maximum pore size by nearly 6.7 times. (4) The microstructural diagram reveals that in the absence of GO, various pores, micro-cracks, spherical voids, and loose cementitious materials appear on the concrete microsurface. However, with the addition of 0.3 wt.% GO, only a limited number of pores and voids are observed. This study establishes a novel dosage-microstructure-property paradigm where 0.3 wt.% GO optimally balances processability (ensured by rheology) with performance (driven by pore homogenization and accelerated hydration). These results inform the optimization of mix designs for additive manufacturing of cementitious composites.