Ultra-high-performance concrete (UHPC) is a form of cementitious composite that has been the most innovative product in concrete technology over the last three decades. Ultra-high-performance concrete has been broadly employed for the design of numerous forms of construction owing to its excellent mechanical characteristics and durability, and studies on its behavior have grown fast in the last decades. While the utilization of ultra-high-performance concrete in bridge engineering (BE) is limited owing to its high costs, little is recognized about the utilization of UHPC in various BE elements. As a result of these issues, a comprehensive review of the current UHPC development trends should be conducted to determine its present state and perspective. This study presents a review of the state-of-the-art UHPC applications in BE. This review also discusses the current status, limitations, challenges, and areas for the further investigation of UHPC in BE. The aim of this research to help various construction stakeholders understand the distinctive characteristics, benefits, and barriers to the broad utilization of ultra-high-performance concrete applications. The understanding of UHPC will aid in increasing its entire market share in both the national and worldwide building sectors.

This review examines the impact of recycled aggregates (RAs) on the fresh and mechanical properties of high-strength concrete (HSC). The results revealed that incorporating RAs can reduce the compressive strength of HSC by up to 25%, with strength values ranging from 40 to 70 MPa depending on the RA content. The addition of supplementary materials like silica fume, fly ash, and polycarboxylate ether significantly mitigated these negative effects, enhancing the compressive strength by approximately 15–20% compared with the control mixes without additives. Furthermore, the tensile strength was observed to decrease by up to 18% with increasing RA content, but fiber reinforcement improved this by 10%, demonstrating the potential of additives to offset mechanical weaknesses. The modulus of elasticity also declined by up to 30% with higher RA dosages, highlighting the critical impact of the adhered mortar quality on the overall stiffness of the concrete. According to the literature, it was noticed that, when the dosage of RCAs is increased, there is a drop in the strength activity index (SAI). When the substitute dosage exceeded 50%, the SAI decreased. These findings underscore the importance of using optimized additive combinations to improve the mechanical performance of RA concrete, making it a viable option for sustainable construction. Overall, the findings suggest that, although RAs may negatively affect certain physical traits of HSC, the use of appropriate additives can optimize its performance, making it a viable option for sustainable construction practices.

This study develops a Gâteaux differential-based mixed finite element formulation for bi-directionally functionally graded (BDFGM) Timoshenko beams graded along both the length and the thickness. The local effective properties are evaluated by the Mori–Tanaka scheme using two independent gradation indices, n_x and n_z, so that the section stiffnesses vary continuously along the beam axis. The axial strain is condensed under the zero-axial-force condition, and extension–bending coupling is retained through a spatially varying condensed bending stiffness. A two-node element with four independent fields (transverse displacement, rotation, bending moment, and shear force) is derived, and its variable bending and shear compliances are integrated by Gauss–Legendre quadrature. In the through-thickness limit (n_x = 0), using the rule of mixtures of the reference solutions, the present deflections agree with refined-theory benchmarks to within about 0.1%; mesh and quadrature studies confirm convergence for the bi-directional case. For n_z = 1 and k_s = 5/6, increasing n_x from 0 to 5 increases the maximum nondimensional deflection by about 59%, from 0.69465 to 1.10563 for L/h = 4 and from 0.61036 to 0.97469 for L/h = 16. For n_x = n_z = 1, replacing k_s = 1 by 5/6 increases the deflection by about 2.3% for L/h = 4 but by only 0.16% for L/h = 16.