PT-EXPERT Method Statement for Post-Tensioning Operations

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1. Introduction

PT-EXPERT is committed to delivering safe, efficient, and high-quality post-tensioning solutions. This Method of Statement outlines the step-by-step procedures for various post-tensioning operations, including installation, stressing, grouting, and truncating existing tendons. All procedures are carried out in compliance with relevant engineering standards and best practices to ensure the safety and durability of structures.

The following document is a comprehensive guide that provides practical advice on the correct methods of installing, stressing, grouting, and truncating mono-strand post-tensioning systems. It is intended to improve workplace quality, safety, and performance in post-tensioning operations.

2. Scope

This Method of Statement applies to mono-strand post-tensioning systems in building slabs. It covers the following core operations:

  • Installation of post-tensioning tendons
  • Stressing operations
  • Grouting procedures
  • Truncating existing tendons
  • Quality control measures

The guidance provided is specific to building structures and does not cover multi-strand post-tensioning or civil structures such as bridges, dams, or rock anchors.

3. Planning and Preparation

Proper planning and preparation are essential to ensure the success of post-tensioning operations. The planning process should involve consultation with all stakeholders, including suppliers, design engineers, principal contractors, safety officers, and employee representatives.

3.1 Site Assessment

  • Verify that the site is adequately prepared for post-tensioning operations.
  • Ensure that scaffolding and perimeter safety screens are in place and suitable for the intended purpose.
  • Confirm that formwork is structurally sound and capable of supporting the weight of tendons and other construction loads.

3.2 Communication

Effective communication between all involved parties is vital to ensure a safe working environment. Key personnel to communicate with include:

  • Design Engineers
  • Principal Contractors
  • Formwork Supervisors
  • Steel Fixing Supervisors

Clear communication helps prevent risks and ensures that all trades working in the immediate area are aware of post-tensioning activities.

3.3 Equipment and Material Checks

  • Inspect all equipment to ensure it is in good working condition.
  • Ensure that post-tensioning materials, including strands and anchorages, are stored properly to prevent damage or corrosion.
  • Verify that calibration certificates for stressing jacks and gauges are up-to-date and available on-site.

4. Safe Work Practices

Safety is paramount during post-tensioning operations. The following practices should be adhered to:

4.1 Personal Protective Equipment (PPE)

All personnel must wear appropriate PPE to minimize risks associated with post-tensioning work. This includes:

  • Safety helmets
  • Safety boots
  • Gloves
  • Eye protection
  • Hearing protection
  • Long sleeves and trousers
  • Full-face shields for angle grinding operations

4.2 Scaffolding and Working Platforms

  • Scaffolding must be properly erected and inspected by a competent person.
  • Ensure that scaffolding platforms are fully boarded with guard rails and toe boards in place.
  • Leave adequate clearance for stressing jacks and barricades.

4.3 Material Handling and Protection

  • Protect post-tensioning materials from corrosion, kinks, and mechanical damage.
  • Store strands vertically and ensure they are chocked to prevent rolling.
  • Do not drag coils of strand to avoid damaging the outer layer.
  • Ensure that anchorages are protected from dirt and mechanical damage.

5. Installation of Post-Tensioning Tendons

The installation process involves setting up anchorages, laying ducts, and pushing strands into position. Proper installation is critical to ensure the effectiveness of the post-tensioning system.

5.1 Anchorages

  • Use only anchorages that have been tested and certified to meet the required standards.
  • Ensure anti-burst reinforcement is in place to prevent concrete failure around anchorages.

5.2 Duct Installation

  • Insert ducting into anchorages, ensuring that grout holes are not obstructed.
  • Secure ducts with duct tape to prevent displacement during concreting.
  • Check for any dents, splits, or kinks in the ducting and replace damaged sections.

5.3 Pushing Strand into Ducts

  • Place caution signs and exclusion zones to prevent unauthorized access to the work area.
  • Use a strand pusher machine to feed the strand through the ducts.
  • Ensure that a second team member is positioned at the far end of the duct to guide the strand into the correct position.

6. Stressing Operations

Stressing is a critical phase in post-tensioning. It involves applying a hydraulic load to the strands to achieve the desired level of tension.

6.1 Initial Stressing

  • Ensure that the concrete has reached the required compressive strength before commencing stressing.
  • Apply the initial stressing load as specified in the design.
  • Mark the strands with paint to measure elongation after stressing.

6.2 Final Stressing

  • Erect stressing barricades and place warning signs before commencing final stressing.
  • Follow the designated stressing sequence as per the project drawings.
  • Measure and record the elongation of each strand to ensure compliance with the design requirements.
  • Inspect anchorages and wedges to ensure they are properly seated.

6.3 Safety Precautions During Stressing

  • Do not allow any personnel to stand between the jack and the barricade during stressing.
  • Ensure that the stressing area is flagged and that warning signs are prominently displayed.
  • Stop stressing immediately if any signs of concrete distress are observed near the anchorages.

7. Grouting Procedures

Grouting is an essential step to protect the tendons from corrosion and provide bond between the prestressing steel and the concrete.

7.1 Pre-Grouting Checks

  • Verify the water-cement ratio and ensure that it complies with the project specifications.
  • Check that grout vents are clear and functional.
  • Ensure that sufficient water supply is available and suitable for grouting operations.

7.2 Grouting Process

  • Inject grout continuously from one end of the tendon to the other.
  • Close grout vents progressively as grout emerges to ensure a complete fill.
  • Clean up grout spillages immediately to prevent setting.
  • Do not reuse expelled grout as it may contain impurities.

8. Truncating Existing Tendons

Truncating tendons within existing slabs may be necessary when tendons are cut inadvertently or when sections of a slab require demolition. The following procedure outlines the steps to safely truncate and secure tendons.

8.1 Procedure for Truncating Tendons

  1. Engineering Assessment: The engineer must conduct an analysis of the slab to identify any required strengthening measures.
  2. Strengthening Installation: Implement any necessary reinforcement as per the engineer’s instructions.
  3. Tendon Location: Locate tendons using post-tensioning drawings and verify their positions with a cover meter device.
  4. Recess Excavation: Excavate a recess measuring approximately 500mm in length and 170mm in width along the tendon.
  5. Cleaning and Inspection: Clean the excavated recess and inspect the grout for any defects or voids.
  6. Epoxy Grouting: Fill the recess with an engineer-approved epoxy grout to secure the tendons.
  7. Cutting: Once the epoxy grout has cured, the slab can be cut, and the tendons terminated securely.
  8. Corrosion Protection: Apply an epoxy protective coating to the exposed ends of the tendons to prevent corrosion.
  9. Propping Removal: Temporary propping must remain in place until the engineer authorizes its removal.

9. Quality Control and Inspection

Quality control is integral to ensuring the longevity and safety of post-tensioned structures. PT-EXPERT implements rigorous inspection protocols at every stage of the post-tensioning process.

9.1 Pre-Stressing Inspections

  • Verify that all post-tensioning components are correctly installed as per the design drawings.
  • Check that the concrete has reached the required compressive strength before commencing stressing.

9.2 Post-Stressing Inspections

  • Measure and record the elongation of each strand to ensure it aligns with the design specifications.
  • Inspect anchorages and wedges for proper seating and any signs of damage.

10. Equipment Maintenance

Maintaining post-tensioning equipment in good working order is essential for safe and effective operations. Regular checks should include:

  • Cleaning grout pumps and hoses after each use.
  • Inspecting jack wedges for dirt, grit, and signs of wear.
  • Checking hydraulic hoses for damage or kinks.
  • Ensuring all pressure gauges and jacks have up-to-date calibration certificates.

11. Conclusion

This Method of Statement serves as a comprehensive guideline for safe and effective post-tensioning operations. PT-EXPERT is dedicated to maintaining the highest standards in all projects, ensuring the safety of personnel and the durability of structures.

For more information or assistance, contact PT-EXPERT at: