On June 24, the right-leg tower base and T1 segment tower column of the west cable tower of the Shiziyang Channel, constructed by the Chongqing-based central enterprise CCCC Second Harbor Engineering Co., Ltd., were successfully poured and completed. In this pouring, C80 concrete was successfully applied, and the optimal mix proportion for C80 concrete was determined, verifying the applicability of the newly developed pouring technology, complete sets of equipment, and temperature control measures, laying a solid foundation for the subsequent C80 concrete pouring of the cable tower.

The right-leg tower base of the west cable tower of the Shiziyang Channel was successfully poured and completed.

　　On June 24, the right-leg tower base and T1 segment tower column of the west cable tower of the Shiziyang Channel, constructed by the Chongqing-based central enterprise CCCC Second Harbor Engineering Co., Ltd., were successfully poured and completed.

　　It is worth noting that in this pouring, C80 concrete was successfully applied, and the optimal mix proportion for C80 concrete was determined, verifying the applicability of the newly developed pouring technology, complete sets of equipment, and temperature control measures, laying a solid foundation for the subsequent C80 concrete pouring of the cable tower.

　　As a super project in the Guangdong-Hong Kong-Macao Greater Bay Area, the Shiziyang Channel is the first double-deck river-crossing passage at the Pearl River Estuary. The controlling project, the Shiziyang Bridge, adopts a double-deck steel truss suspension bridge scheme with a main span of 2,180 meters that "crosses the river in a single span," making it the world's largest-span double-deck suspension bridge. Once completed, it will set five world-leading records in "main span length, number of lanes, main tower height, anchorage foundation, and main cable scale."

　　Among them, the cable tower of the Shiziyang Bridge adopts a steel-shell concrete composite bridge tower with a height of 342 meters, also the world's tallest bridge tower of the same type. A single bridge tower consists of 62 segments and 6 steel cross beams.

　　However, adopting a steel-shell concrete composite bridge tower means that the cable tower of the Shiziyang Bridge needs to ensure the mechanical performance of the ultra-high steel plate concrete composite bridge tower, and the steel shell walls will be filled with C80 special concrete featuring high strength, high elasticity, high robustness, and low shrinkage.

　　Prior to this, for the first application of C80 concrete in the structural characteristics of steel-concrete cable towers and the technical difficulties faced in construction, there was no practical experience to draw on.

Super project Shiziyang Bridge.

　　To this end, the Tao Jianfei Innovation Studio team of the CCCC Second Harbor Engineering Testing Center embarked on a research and development journey. First, the project team strictly controlled various performance indicators of raw materials and drafted an initial concrete mix proportion.

　　"In the previous concrete mix proportions, the cement proportion was high, cement hydration heat release was large, and the adiabatic temperature rise of concrete was relatively high, posing a greater cracking risk when applied to solid structures. After several previous tests, the concrete temperature peak still exceeded the requirements, and the tests were unsuccessful," said Wu Yang, director of the project laboratory.

　　Through the accumulation and analysis of multiple test data, the project department optimized the theoretical mix proportion, appropriately reducing the proportion of cement and fly ash while adding a certain proportion of anti-cracking agent and flow modifier. After multiple adjustments, the concrete performance and indicators all met the design requirements. While ensuring concrete strength, its chloride ion diffusion coefficient was improved and its own cementitiousness was enhanced, producing concrete with good workability, low hydration heat, and higher density.

　　June 22 was a day that all team members both looked forward to and felt nervous about—the right-leg tower base and T1 segment tower column of the west cable tower of the Shiziyang Channel officially began pouring.

　　"Attention all groups, during the pouring process you must go slowly and steadily..." The tower base and the T1 segment of the tower column were poured together as a whole, with a total of 1,676.2 cubic meters of C80 concrete poured. The pouring sequence followed "outside first, then inside; from the surroundings to the center; layered alternating pouring" until the concrete was poured to the design elevation.

　　The summer weather was unusually muggy, and the sun in the blue sky was like fire, making everyone sweat profusely. But no one bothered to wipe their sweat, concentrating fully on completing the established actions they had rehearsed countless times before.

　　After 30 hours of shift work, the final batch of concrete was poured. Only then did all team members breathe a sigh of relief, and their anxious hearts finally settled.

T1 segment tower column of the Shiziyang Bridge.

　　Every project has unpredictable technical difficulties; every technical difficulty is a hard nut to crack.

　　Late that night, the small conference room on the second floor of the Shiziyang Bridge project department was still brightly lit, and the sound of whiteboard markers was especially loud. Zeng Wei, the project chief engineer, was leading the technical research team in a summary after the C80 concrete pouring: "After this pouring was completed, 13 indicators including the slump flow, segregation rate, temperature changes, and mechanical properties of the C80 concrete were tested, and all met the design specification requirements."

　　The successful pouring and completion of the right-leg tower base and T1 segment tower column of the cable tower of the Shiziyang Channel not only verified the applicability of the C80 concrete preparation technology and complete sets of pouring equipment, but also pioneered a new path for the construction of similar bridges and provided valuable practical experience.