Fresh-to-Solid Computational Simulations of Additive Manufacturing of Ultra-High-Performance Fiber Reinforced Concrete
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Additive manufacturing of concrete is a topic of interest within academia and industry. Simulating the behavior printable concrete from the fresh state to the hardened state and long-term performance will provide the future engineers with the ability to optimize designs and predict failures of structural elements. A key aspect of concrete additive manufacturing is the complexity of optimization, which includes systems, scheduling, and materials. Our research focuses on simulating the fresh state, hardened behavior, and the transition from fluid-to-solid of nanoclay-modified ultra-high-performance fiber-reinforced concrete system. The Discrete fresh concrete (DFC) model [1] and Smooth Particle Hydrodynamics (SPH) model [2] are studied to model the flow of fresh concrete from both visco-elastic solid contact and non-Newtonian fluid perspectives. A new thixotropy model for the flow of 3D-printed concrete is used to model the rotational rheometer test, flow test, and direct shear test. The DFC model flow is coupled with a mathematical fiber orientation algorithm [3] to generate fiber distribution and alignment according to the flow. Simulations of extrusion from a piston extruder and an auger are performed to obtain the extrusion shape, and surface reconstruction was implemented. The Lattice Discrete Particle Model (LDPM) [4], using the 3D scan surface topography of 3D printed samples, is employed to study the effect of the surface features on the mechanical behavior of reinforced and unreinforced UHPC. Using data from Isothermal Calorimeter and Ultrasonic Pulse Velocity, a coupled DFC and LDPM model is developed, which transitions the behavior from fluid to solid. This opens the pathway to optimize concrete 3D printing designs.