Recently, the spraying UHPC construction technology jointly developed by CCCC Second Harbor Engineering Co., Ltd. and Ocean University of China was successfully applied in the wet junction protection of bridge piers of Hangzhou Bay Sea-Crossing Bridge Concrete Performance Maintenance and Enhancement (2023-2024) Project, which was jointly implemented by the Technology Centre and Construction Technology Branch of CCCC Second Harbor Engineering Co., Ltd. The successful implementation of spraying UHPC technology for wet junction protection provides new productivity for the development of reinforcement and protection technology for offshore structures.

Hangzhou Bay Sea-Crossing Bridge is located in Hangzhou Bay, one of the world's three strong tidal waters, there are stormy waves, high tidal range, strong currents, harsh environments in this region. The wet junctions of the bridge piers after 15 years of service has appeared cracks, defects, and other typical diseases, the application is aimed at repairing the existing structure while improving the overall durability.

Aiming at the short window of this project, harsh material performance requirements, difficulties in construction organization and other characteristics, the project team upgraded the technology on the basis on the first generation, creatively developed with ultra-long slump retaining, ultra-long-distance pumping, ultra-fast hardening, ultra-high strength and ultra-high impermeability and other performance of the complete set of construction technology of spraying UHPC. The slump retaining time is more than 4h, the pumping distance is more than 50m, the setting time is less than 10min, 1d compressive strength is more than 80MPa, seepage resistance grade P40 or more. The slump time of sprayed UHPC is more than 4h, pumping distance is more than 50m, setting time is less than 10min, 1d compressive strength is more than 80MPa, and impervious grade is more than P40.

Photo of the wet junction of bridge pier after the sprayed UHPC protective construction

The research and development of complete set of spraying UHPC technology took 4 years, during which it was supported by the‘14th Five-Year Plan’ Shandong Province Key R&D Programme and CCCC Applied Basic Research Project, and formed a series of material-equipment-construction products and services, such as special rheology modifier, agglutinating agent, premixture, wet spraying machine and spraying construction, which have broad application prospects in the fields of repair and reinforcement of existing structures, tunnel support, protection and life extension of marine structures, structural waterproofing and corrosion protection, and so on. It has broad application prospects in the fields of repair and reinforcement of existing structures, tunnel support, protection and life extension of offshore structures, and waterproofing and anticorrosion of structures.