Experimental study on the effect of carbon fiber on rheological and mechanical properties of 3D printed steel slag cementitious materials

The high carbon emission of concrete is mainly related to the large amount of cement used in concrete, and the use of bulk solid waste to prepare green high-performance concrete provides a new development path for the realization of the goal of "double carbon&#34. Steel slag and blast furnace slag were used to replace part of the cement as cementitious material, and carbon fiber was used as a reinforcing material to prepare 3D printed fiber-reinforced steel slag cementitious material, and its rheological and mechanical properties were tested, and SEM, low-field NMR, and X-CT were used to analyze the influence of the fibers on the toughening of its mechanical properties. The results showed that with the increase of carbon fiber doping, the dynamic and static yield stresses and plastic viscosity increased, and the thixotropic index, thixotropic ring area and viscosity recovery rate peaked and then decreased when the carbon fiber doping increased to 0.4%. The flexural, compressive and splitting strengths increased with increasing carbon fiber doping. Compared with cast specimens, 3D printed specimens showed anisotropy, specifically compressive strength X direction > Y direction > Z direction, flexural strength Y direction > Z direction > X direction, and splitting strength Z direction > X direction > Y direction. Using SEM, LF-NMF and X-CT methods, it was learned that the carbon fibers were directionally distributed and well dispersed in the 3D-printed materials, and the carbon fiber incorporation effectively reduced the porosity of the 3D-printed specimens and significantly improved the mechanical properties.