Fresh and anisotropic-mechanical properties of 3D printable ultra-high ductile concrete with crumb rubber

This study developed a novel ultra-high ductile concrete (UHDC) for 3D concrete printing, which was modified using crumb rubber to possess high ductility. Flowability tests were conducted to determine optimal open time range for continuous printing. A series of mechanical tests, including uniaxial tensile test, compressive test, flexural test and double shear test, were carried out to investigate the anisotropic-mechanical properties of the printed UHDC. The results indicate that the tensile strength, flexural strength and shear strength of the printed specimens were slightly lower than those of mold-cast specimens, while reverse tendency was observed in compressive strength. It is of interest that the deformability and energy dissipation of the printed UHDC at some directions are higher than those of mold-cast UHDC. Additionally, it is found that the printed UHDC performed minimal anisotropy in flexural strength, but significant anisotropy in flexural deformability, compressive and flexural energy dissipation capacity.