%T A Comprehensive Review on Ultra-High Performance Concrete: Composition, Properties, and Applications %J Journal of Civil Engineering and Urbanism %K Ultra-High Performance Concrete (UHPC), Mechanical properties, Durability, Seismic performance, Fiber reinforcement, Sustainability. %N 2 %D 2025 %I Scienceline Publication %A Tamkin Karimi %V 15 %L eprints1387 %P 77-111 %R 10.54203/jceu.2025.6 %X Ultra-High Performance Concrete (UHPC) has emerged as a leading construction material across diverse engineering applications due to its exceptional mechanical properties and durability that exceed those of conventional concrete. This comprehensive review explores UHPC’s material composition, production additives, behavior in both fresh and hardened states, and environmental durability characteristics. The low water-to-cement ratio combined with a high binder content and the use of superplasticizers result in a densely compacted microstructure, substantially enhancing UHPC’s strength. Pozzolanic additives—including silica fume (SF), metakaolin (MK), fly ash (FA), and ground granulated blast furnace slag (GGBFS)—contribute to reduced cement consumption while improving long-term durability by enhancing permeability resistance, sulfate attack mitigation, and chloride ion durability. The integration of nanomaterials such as nano-silica (NS), carbon nanotubes (CNT), and graphene oxide (GO) increases the reactive surface area within the matrix, leading to a more uniform and denser microstructure. Fiber reinforcements—comprising steel, synthetic, glass, or hybrid fibers—impart ductility to UHPC, significantly boosting tensile and flexural strengths as well as energy absorption capacity, complementing its notable compressive strength. Fresh-state properties such as consistency, slump, and flowability are critical for manufacturability and application quality, with optimized mixtures delivering superior structural performance in terms of impact resistance, fatigue durability, and fracture mechanics. Additionally, UHPC demonstrates outstanding resistance to freeze-thaw cycles, sulfate and acid attacks, and chloride ingress, making it highly suitable for infrastructure exposed to aggressive environments. This review synthesizes the current understanding of UHPC’s technical advancements and multifaceted benefits, positioning it as a next-generation sustainable construction material that meets the demanding requirements of modern infrastructure.