Influence of nano-coated micro steel fibers on mechanical and self-healing properties of 3D printable concrete using graphene oxide and polyvinyl alcohol

High ductility cementitious composite is one of the proposed new generations of concrete for use in 3D concrete printing with a large dosage of microfibers. This large volume of fibers negatively affects printed layers' fresh properties and durability. It also increases the porosity of concrete and is not cost-effective. Accordingly, through an experimental program, this article introduces a novel coating technique to reduce the required quantity of fibers for 3D concrete printing. Polyvinyl alcohol (PVA) is used in the present study to help in coating graphene oxide (GO) nanomaterials on the surface of micro steel fibers. Compressive, direct tensile, and bending tests are considered for the mechanical properties. The self-healing property of the proposed mixture is also checked by applying pre-loading on direct tension and bending samples and followingly putting for the healing period. The results show that the nano-coating method improves the compressive and direct tensile strength of cement mortar so that this technique can be used to reduce the volume percentage of steel fibers to achieve the same mechanical characteristics. Also, promising findings were obtained for the self-healing properties of cementitious composites containing nano-coated fibers.