Experimental Investigation of Mechanical Properties of Ultra-High-Performance Concrete

This study presents a comprehensive experimental and numerical investigation into the structural performance of Ultra-High-Performance Reinforced Concrete (UHPRC) rectangular columns subjected to varied loading conditions, with the objective of improving strength, ductility, and service life in modern construction. UHPRC, recognized for its exceptional compressive strength, tensile capacity, and long-term durability, holds significant promise for critical structural elements exposed to demanding environments. The research focuses on evaluating the behaviour of UHPRC rectangular columns under axial loading, uniaxial bending, and biaxial bending, while analysing the influence of concrete grade, reinforcement ratio, and loading type on load-bearing capacity and failure characteristics. A total of eighteen rectangular column specimens were designed, cast, and tested using a 2000 kN capacity loading frame. The experimental program incorporated three concrete grades (M60, M70, M80), three reinforcement ratios (1.34%, 2.09%, 3.01%), and three loading scenarios. This experimental matrix facilitated an in-depth assessment of material and loading interactions. Finite Element (FE) models, comprising both two-dimensional plane stress elements and a full three-dimensional representation, were developed to simulate column behaviour. Model validation against experimental outcomes and existing literature confirmed their reliability in predicting peak loads, crack propagation, and post-cracking response. The results revealed that UHPRC significantly enhances peak load capacity and ductility, with higher concrete grades and reinforcement ratios delivering superior performance. Failure patterns exhibited gradual post-cracking behaviour, indicating improved energy dissipation. Furthermore, a simplified analytical model was formulated and calibrated to predict load–moment interaction, showing close agreement with experimental and numerical results. This study confirms UHPRC’s potential for improving the safety, durability, and efficiency of rectangular column design, offering valuable guidance for its implementation in high-performance structural systems.