Evolution of ultra high performance concrete using hybrid fibers: a review
Ban Ahmed Khaleel, Eethar Thanon Dawood
Abstract
Ultra-High Performance Concrete (UHPC) is a modern composite material that combines high strength, durability performance with increased toughness and service life making it suitable for high-performance structural applications in infrastructures. However, the application of UHPC in tensile and dynamic loads makes it brittle and as a result, fibers are essential to enhance its performance. Single fiber systems (metallic or polymeric) have been explored extensively, and for most of them, the mechanical properties and the durability improvements are somewhat unequal. However, to meet this, a relatively new solution known as hybrid fiber systems has gained popularity by combining different types of fibers to improve composite performance. Based on the features of hybrid fibers, this review provides a critical evaluation of the literature on concrete containing UHPC in terms of compressive strength, tensile resistance, flexural toughness, and durability. The Hybrid Fiber Synergy is introduced and discussed to demonstrate that when fibers with different mechanical characteristics, sizes, and roles are placed together, they will work even better. However, some of the drawbacks include the high costs of installation and the lack of convincing long-term results to complement the gains noted. Based on the gap analysis of this review, this section presents directions for future studies and area recommendations for future research with a focus on incorporating hybrid fibers with advanced technologies, such as three-dimensional printing, and machine learning. The results further show the added values of hybrid fibers in promoting UHPC toward more progressive and efficient construction solutions.