Research On Preparation And Performance Of 3D Printing Fiber Reinforced Concrete

3D printing concrete technology is a research hotspot in the field of construction.This technology combines concrete materials with advanced 3D printing technology to lead the building construction into a new era of information and mechanization.In recent years,domestic and foreign scholars have conducted comprehensive research on3 D printing concrete technology,and have made significant progress in the structure and performance parameters of 3D printers,and the design of material mix ratio.Based on the existing research results,this paper studies the rheological properties,printability and mechanical properties of flexible fiber-reinforced 3D printed concrete,explores the mechanism of the effect of flexible fibers on the performance of 3D printed concrete,lay the foundation for the rational use of flexible fiber reinforced 3D printed concrete.This article mainly contains the following research contents.(1)Study the mix ratio of 3D printed concrete and test the rheological properties,and the rheological properties,printability,and mechanical properties of materials with different B/S and W/B ratios were tested.Finally,the J800 compounding ratio of rubber-sand ratio close to 1 was used as the matrix of the fiber reinforcement material,and the amount of the additive was increased based on it to adapt to the influence of the fiber on the material flowability,and to increase the selection range of fiber incorporation and length.(2)This study proposes a quick test method and a stable test method for the printability of 3D printed concrete to evaluate the printability of 3D printed concrete,and verifies the feasibility of the above method through experiments.The test results show that the incorporation of flexible fibers will reduce the printability of the material.But by setting the extrusion speed of the 3D printer,fiber-reinforced materials with different rheological properties can be printed with the same print quality.(3)The effects of three kinds of flexible fibers with different dosage and length on the rheological properties,printability and mechanical properties of 3D printed concrete were studied,and the applicable range of flexible fiber dosage and length was summarized.The research results show that PP fiber with a diameter of about 130 μm has little effect on the rheological properties of 3D printed concrete,and has a significant effect on the compressive strength and interlayer bonding strength of the material.The applicable volume content is 0.3% and the fiber length is less than 6mm.Sisal fiber can steadily improve the printability and flexural strength of the material.The applicable volume content is less than 0.3% and the length is about 6mm.PVA fiber has a significant degradation effect on the rheological properties and mechanical properties of the material.(4)Combined with the morphology map of flexible fibers,CT micromorphology test results,and the rheological properties and mechanical properties of fiber-reinforced3 D printed concrete,the mechanism of the rheological properties and mechanical properties of 3D printed concrete was analyzed.The research results show that the fiber aspect ratio and surface properties are important factors affecting the printability of 3D printed concrete.Synthetic fibers with a diameter greater than 100 μm,a length of about6 mm,and good hydrophilicity have little effect on the printability of the overall material,and can be used to enhance the performance of 3D printed concrete;Hygroscopic plant fibers can significantly enhance the printability of 3D printed concrete;The incorporation of flexible fibers changes the number of fibers at the 3D printed concrete interface and the overall porosity and pore volume of the material,which in turn affects the mechanical properties of the material.