Bucket Placing Underwater Concreting

Bucket Placing Underwater Concreting

Overview

• Definition: Bucket placing underwater concreting is a technique used to place concrete in underwater environments using a bucket or skip.

Key Points

1. Purpose and Application

   • Used in constructions involving underwater structures like piers, bridges, dams, and marine structures.
   • Ensures that concrete is placed without segregation or washout by the surrounding water.

2. Bucket Design

   • Types of Buckets: Open or closed configuration.
   • Capacity: Ranges from small (for specialized applications) to large volumes (for substantial underwater works).
   • Mechanisms: Equipped with a bottom opening mechanism, controlled from the surface to release concrete at the desired location.

3. Quality of Concrete

   • Mix Design: Adapted for underwater applications; typically includes anti-washout admixtures to maintain cohesion and reduce separation.
   • Slump: High-slump concrete often used to ensure flowability under water.

4. Placement Procedure

   • Preparation: Site preparation includes cleaning the underwater surface area.
   • Positioning: The bucket is lowered carefully to avoid disturbing the water and sediment.
   • Discharge: Concrete is discharged slowly and evenly; the bucket is not lifted until the concrete starts to flow out.
   • Sequential Layering: Placement done in sequential layers to ensure proper compaction and integrity.

5. Advantages

   • Controlled Placement: Minimizes segregation and washout.
   • Versatility: Can be used in various underwater conditions including strong currents.
   • Cost-Effectiveness: Reduces the need for additional expensive underwater equipment.

6. Limitations

   • Access and Maneuverability: Limited by the size and depth of the underwater area.
   • Visibility: Low visibility underwater can complicate the placement process.

7. Safety and Environmental Considerations

   • Diver Safety: Ensuring the safety of divers and operators is paramount; proper communication and planning are essential.
   • Environmental Impact: Measures to mitigate the impact on marine ecosystems, including careful handling of materials to prevent contamination.

8. Maintenance and Monitoring

   • Regular Inspections: Essential to ensure the structural integrity of the concreting works.
   • Repairs: Periodic maintenance and repairs may be required due to underwater conditions.

Detailed Aspects

• Admixtures Used:

  • Anti-washout admixtures
  • Water reducers
  • Plasticizers

• Innovations:

  • Advanced polymers
  • Self-consolidating concrete formulations

• Technical Specifications:

  • Pressure Maintenance: Atmospheric vs. hydraulic pressures managed carefully.
  • Flow Rate: Careful control to maintain a continuous and even flow.

Summary

• Bucket placing underwater concreting is a specialized technique for constructing underwater structures.
• Key considerations include concrete mix design, bucket mechanisms, and precise placement procedures.
• Advantages focus on controlled placement and cost-effectiveness, while limitations deal with accessibility and environmental impacts.
• Safety protocols and regular monitoring are crucial to the success and longevity of underwater concreting projects.