Long-term stability of ultra-high-performance concrete with steel fibers in various environments

Ultra-high performance concrete (UHPC) is renowned for its exceptional strength, durability, and structural integrity, offering sustainable solutions for construction. However, concerns persist regarding its long-term performance under various environments due to unhydrated cementitious particles. This study investigates the effect of steel fiber content on the long-term stability of UHPC in tap water, outdoor, and seawater environments over 720 days. Results show that adding 1%∼3% steel fiber increases compressive strength by 4.5%∼11.5%, 9.5%∼18.5%, and 0.4%∼3.5%, respectively. Steel fibers effectively reduce length changes, decreasing the rate by 26.3%, 57.0%, and 26.3%, respectively. Microstructure analysis confirms the formation of calcite and brucite in seawater, indicating chemical interactions between seawater components and cement-based materials. After 720 days in seawater, surface fibers exhibited corrosion, but internal fibers remained intact. This study provides insights into UHPC's long-term stability in diverse environments, critical for infrastructure durability and safety.