Preparation and Application of C55 Steel Tube Arch Manufactured Sand Micro-Expansion Self-Compacting Concrete

Literature Overview

This research paper, authored by Zhang Yi, He Bei, Ren Qiang, Jiang Zhengwu, Song Junxi, and Mu Jinwei, presents the development and practical application of a C55 grade self-compacting concrete incorporating manufactured sand and micro-expansion properties for steel tube arch bridge construction. Published in Construction Technology in 2022, the study addresses the growing need for manufactured sand to replace depleting natural river sand resources. The research was supported by multiple National Natural Science Foundation grants.

Research Background and Technical Challenges

The depletion of natural river sand resources has driven the development of manufactured sand as a sustainable alternative for concrete production. However, manufactured sand presents several challenges for use in high-performance concrete applications, particularly in steel tube concrete structures where workability, strength, and compatibility with the steel tube are critical requirements.

The specific challenges addressed in this research include:

• Achieving self-compacting properties with manufactured sand, which typically has irregular particle shapes and higher water demand
• Ensuring adequate expansion properties to compensate for shrinkage and ensure full filling of the steel tube
• Achieving C55 strength grade while maintaining workability for placement within confined steel tube spaces
• Ensuring long-term durability and compatibility with steel tube materials

The project requirements for the Wumei River Grand Bridge specified high-performance concrete that could be self-placed within steel tubes without vibration, achieve high strength, and provide adequate expansion to ensure full concrete-steel tube bonding.

Concrete Mix Design Optimization

The research employed a systematic approach to optimize the concrete mix design, focusing on four key optimization strategies:

The resulting concrete mix achieved the following performance characteristics:

• Expansion degree: greater than 650 mm (flow table)
• Slump flow: greater than 270 mm (funnel flow)
• Time-dependent loss: nearly zero at 5 hours
• Compressive strength: C55 grade
• Expansion properties: micro-expansion for full steel tube filling

The achievement of these performance targets demonstrates the feasibility of using manufactured sand in high-performance self-compacting concrete for steel tube applications. The near-zero time-dependent loss at 5 hours is particularly significant for construction scheduling, as it allows for flexible placement timing without significant loss of workability.

Mechanical Properties and Performance

The mechanical properties of the C55 manufactured sand self-compacting concrete were evaluated through compressive strength tests, splitting tensile strength tests, and elastic modulus measurements. The results demonstrated that the manufactured sand concrete achieved comparable or superior mechanical properties to conventional natural sand concrete of the same strength grade.

The micro-expansion properties were verified through expansion tests and confirmed to be adequate for ensuring full filling of the steel tube without voids or honeycombing. The expansion was controlled to prevent excessive pressure that could damage the steel tube or cause surface cracking of the concrete.

The workability retention over time was a critical finding, as it directly impacts construction practicality. The near-zero loss of flowability at 5 hours means that concrete can be transported and placed within a generous time window, reducing the risk of placement defects due to workability loss.

Application in Wumei River Grand Bridge

The successful application of the developed concrete in the Wumei River Grand Bridge project provided real-world validation of the research findings. The bridge construction required the placement of large volumes of self-compacting concrete within steel tubes, presenting challenges related to:

• Continuous placement without vibration
• Maintaining workability during extended placement periods
• Achieving uniform concrete quality throughout the steel tube length
• Ensuring proper bonding between concrete and steel tube

The construction team reported that the self-compacting properties of the concrete eliminated the need for vibration, reducing construction time and labor requirements. The micro-expansion properties ensured full filling of the steel tube without voids, providing excellent composite action between the steel tube and concrete infill.

Quality control during construction included regular testing of fresh concrete properties, including flow table, funnel flow, and air content. Hardened concrete strength was verified through cube testing and non-destructive testing methods. The construction results confirmed that the manufactured sand self-compacting concrete performed reliably in the actual bridge construction environment.

Engineering Practice and Quality Control

The successful application of manufactured sand self-compacting concrete in the Wumei River Grand Bridge provides a template for similar projects. Key quality control measures that should be implemented include:

• Pre-construction mix design approval and trial batching
• Continuous monitoring of fresh concrete properties during placement
• Regular testing of hardened concrete strength and expansion
• Documentation of placement conditions and any deviations from standard procedures
• Post-construction inspection of steel tube filling quality

The use of manufactured sand in high-performance concrete requires careful attention to aggregate quality control. The particle size distribution, shape, and surface texture of manufactured sand must be optimized to achieve the desired concrete properties. Regular testing of manufactured sand quality is essential to maintain consistent concrete performance.

Study Insights and Conclusions

This research demonstrates that manufactured sand can be successfully used in high-performance self-compacting concrete for steel tube applications. The systematic mix design optimization approach provides a replicable methodology for developing similar concretes for other projects. The successful application in the Wumei River Grand Bridge validates the technology for practical construction use.

The achievement of near-zero workability loss at 5 hours is a significant practical advantage that should be highlighted in future specifications. This property provides construction flexibility and reduces the risk of placement defects. The micro-expansion properties ensure reliable steel tube filling, which is critical for achieving the full composite action between steel and concrete.

The economic and environmental benefits of using manufactured sand instead of natural river sand are substantial. The research contributes to sustainable construction practices by demonstrating that high-performance concrete can be produced using locally available manufactured sand resources. Future research should focus on long-term durability, carbonation resistance, and chloride ingress resistance of manufactured sand concretes in aggressive environments.

Overall, this paper represents a significant contribution to the field of concrete technology and provides engineers with a proven technology for sustainable steel tube concrete construction. The successful application in a major bridge project demonstrates the practical viability and reliability of the developed concrete technology.