Material design and performance optimization of eco‐friendly manufactured sand ultra‐high performance concrete for bridge joints

Manufactured sand ultra‐high performance concrete (UHPC) provides a sustainable and cost‐effective alternative to quartz sand UHPC for wet joints in prefabricated bridges. However, the angular particle shape, rough surface texture, and stone powder contained in manufactured sand may influence the flowability, hydration, shrinkage, and mechanical performance of UHPC. In this study, a manufactured sand UHPC mixture was developed for bridge wet joints based on dense packing principles. The effects of water to binder ratio, stone powder content, and steel fiber content on fresh properties, hydration heat, shrinkage behavior, and mechanical performance were systematically investigated. The results show that an appropriate stone powder content improves matrix packing and strength development, while steel fibers enhance tensile and flexural performance and restrain shrinkage within an optimal content range. The optimized mixture with a water‐to‐binder ratio of 0.18, 3% stone powder, and 2% steel fiber achieved mechanical properties comparable to those of conventional UHPC, while maintaining a moderate hydration temperature rise and favorable volume stability. On‐site sampling from prefabricated bridge wet joints further confirmed that the proposed UHPC satisfied the specified construction and mechanical performance requirements. Nevertheless, the higher microstrain observed at the bridgehead suggests that enhanced curing control is required in this region. These findings provide a practical material design strategy and engineering application evidence for promoting the sustainable application of manufactured sand UHPC in prefabricated bridge joints.