Rheological and Mechanical Properties of Polyformaldehyde-Fiber-Reinforced 3D Printed High-Strength Concrete with the Addition of Fly-Ash (2024-11)¶

3D printing concrete (3DPC) technology is a relatively new and rapidly developing technology in the construction industry recently, often employing the addition of external fibers to enhance its rheological and mechanical properties. Polyoxymethylene (POM) fibers have a broad research prospect due to their good compatibility with inorganic materials and resistance to alkali. This study investigates the rheological and mechanical properties of 3D-printed high-strength concrete which contain POM fibers. The study examines the effects of POM fiber volume fraction (1.5%, 2%, 2.5%) and fly ash content (0%, 10%, 20%) on the rheological and mechanical properties of 3D-printed concrete, and evaluates the yield stress and plastic viscosity at different volume fractions, and the effects of different fiber contents on compressive and flexural strength were evaluated through compression and bending tests. The study also characterizes the microstructure using scanning electron microscopy. The results show that POM fibers will significantly improve rheological parameters, and fly ash will effectively improve rheology, making 3DPC able to meet the requirements of workability. The maximum enhancement in compressive and flexural strength were both observed at 2% POM fiber volume, providing optimal balance between rheology and strength. In addition, the effect of fiber orientation arrangement on strengthening compressive and flexural strength was proved by microscopic tests. These results can provide an important experimental reference for evaluating the rheological and mechanical properties of 3D-printed fiber-reinforced concrete.