Fiber Orientation in Ultra High-Performance Concrete: Quantification, Characterization, and Implications for Design and Performance, Part 1 (ACI Spring 2024, New Orleans, LA) The alignment and uniform distribution of steel fibers within ultra-high-performance concrete (UHPC) are essential for optimizing its structural performance. These factors are determined during the casting phase when the concrete is still in its fluid state. To comprehensively analyze how variables such as fresh UHPC rheology, fiber type, reinforcing bars, and casting equipment influence fiber orientation and distribution, a robust predictive tool is required. This tool should be capable of simulating the microscale interactions between the fluid mortar and the embedded fibers. To this end, we will employ a synergistic approach that integrates Computational Fluid Dynamics (CFD) with Discrete Element Methods (DEM), a combination proven effective in elucidating complex multiphase flows. The accuracy of the CFD model will be initially confirmed through comparisons with controlled laboratory experiments. Subsequently, advanced imaging techniques will be employed to register the fiber movements, providing a basis for comparing and validating the DEM predictions. The findings from this comprehensive evaluation will constitute the main focus of the forthcoming presentation.

Fiber Reinforced Concrete and Ultra High Performance Concrete for Durable Structures - Case Studies (ACI Spring 2024, New Orleans, LA) The demand for sustainable, durable and resilient infrastructures has never been as important as of today to ensure progress and growth of our modern society as well meeting our long term sustainability goals. The presentation will focus on actual durability and mechanical performances obtained during the production of high performance fiber reinforced concrete for heavy infrastructure projects. Some mix design aspects as well as critical production and quality control protocols to achieve consistent high performance results will be discussed.