Influence of constituent materials on the mechanical properties and durability of Ultra-High Performance Fiber Reinforced Concrete (UHPFRC): A critical review

Ultra-High Performance Fiber Reinforced Concrete (UHPFRC) is a cementitious composite with excellent mechanical behavior and high durability due to its dense matrix. There are many studies investigating the mechanical behavior of UHPFRC; however, there are fewer studies relating the microstructure properties to the structural response of the composite. This understanding allows the development of more efficient, economical, and sustainable characteristics. In this sense, this paper addresses a literature review on UHPFRC to investigate how the constituent materials influence the concrete mechanical properties and durability. The study focuses on crucial factors, such as aggregates, fibers, water-cement ratio, and their direct influence on mechanical responses, such as strength, workability, and hardness. Some highlights are: (i) the importance of aggregates in the final performance of concrete and the influence of their characteristics on durability and structural performance; (ii) the importance of the water-cement ratio, which is a determining factor in the workability of UHPFRC, its mechanical properties and the formation of the microstructure; (iii) the role of fibers in improving tensile strength and dynamic behavior, with the geometric and mechanical characteristics of fibers, as well as their content and orientation, being critical. This study shows the importance of the material selection and mixture preparation stages based on the various aspects investigated and the need for advances in experimental/numerical research that allow a greater understanding of UHPFRC to develop concretes that are more adapted to reality, thus meeting the structural needs and current challenges of civil construction, as well as the lack of more efficient and sustainable materials.