Experimental Study on Uniaxial Compression Stress-Strain Relationship of Hybrid Fiber-Reinforced Coral Sand Ultra-High Performance Concrete.

The utilization of coral aggregates in the preparation of Ultra-High Performance Concrete (UHPC) effectively addresses the material scarcity challenges in island and reef construction environments, thereby advancing the sustainable development of building materials technology. This research systematically investigates the physical and mechanical properties of Coral Sand UHPC (CSUHPC) with varying fiber contents through uniaxial compression tests, splitting tensile tests, and stress-strain curve tests under compression. The experimental results demonstrate that the incorporation of fibers significantly enhances both the mechanical strength and ductility of CSUHPC. The test data indicate that CSUHPC specimens with a steel fiber volume fraction of 3% exhibit the highest performance, attaining a compressive strength of 131.9 MPa and a splitting tensile strength of 18.5 MPa. The compressive stress-strain curve tests reveal that the incorporation of fibers induces a failure mode transition in CSUHPC specimens from brittle to ductile. Furthermore, a constitutive equation for CSUHPC was proposed, and a multi-dimensional assessment system based on the radar chart, which encompasses compressive strength, splitting tensile strength, peak strain, compressive toughness, and an energy dissipation coefficient. The optimal fiber combination was determined as a hybrid fiber system comprising 2% steel fibers and 1% polyethylene (PE) fibers, which demonstrates superior comprehensive performance.