uncoated stress-relieved strand for prestressed concrete

IS 6006 - Scope: Key Specifications and Tables

IS 6006 covers 7-wire steel strands used in prestressed concrete, specifying dimensions, tolerances, physical properties, and mechanical requirements.

1. Dimensions & Tolerances (Clause 4.3, Table 2)

IS 6006: Definitions & Key Specifications for Seven Wire Strands

1. Definitions (Clause 2.0)

• Standard definitions apply to strands, including nominal cross-sectional area and nominal mass (informative only).

2. Physical & Mechanical Properties (Clause 6.2, Table 6)

3. Dimensional Tolerances & Mass (Clause 4.3, Table 2)

| Class | Designation | Nominal Diameter (mm)

IS 6006: Material Requirements for Seven-Wire Strands

1. Physical & Mechanical Properties (Clause 6.2)

2. Dimensional Tolerances & Mass (Clause 4.3)

IS 6006: Size and Designation of Wire Strands

Key Tables & Specifications

1. Size and Designation (Clause 4.2 & 4.3)

Seven-wire strands (Class 1 & 2):

2. Minimum Breaking Load & 0.2% Proof Load (Clause 6.2)

IS 6006: Dimensions and Tolerances for Wire Strands

Key Tables Summary

Table 1: Two and Three Wire Strands (Clause 4.2 & 5.1)

Table 2: Seven Wire Strands (Clauses 4.3 & 5.1)

IS 6006: Mechanical Properties of Seven-Wire Strands

Key Specifications (Clause 6.2 & Tables)

Nominal Dimensions & Mass (Clause 4.3, Table 2)

IS 6006 - Testing Methods: Key Formulas & Tables

1. Minimum Breaking Load & 0.2% Proof Load (Clause 6.2 & Table 3)

2. Load at 1.0% Extension Method (Clause 7.2.1)

• Apply initial load = 10% of minimum breaking load.
• Attach extensometer calibrated to 0.001 mm/mm gauge length.
• Measure load at 1% extension for proof.

3. Strand Dimensions & Tolerances (Clause 4.3, Table 2)

IS 6006: Sampling and Criteria for Conformity

Sampling (Clause 8.1)

• 7-ply strand coils:

  • Random samples from every group of 5 coils.
  • Minimum 2 samples per lot.

• 2-ply and 3-ply strand coils:
  Sample size based on lot size:

Retest Criteria (Clause 8.2)

• If a sample fails, take 2 additional samples from the same coil end.
• If both pass, coil conforms.
• If either fails, coil does not conform.

Relaxation Test (Clause 7.4)

• Initial stress = 70% of specified minimum tensile strength.
• Temperature: 20 ± 2℃.
• Load applied over 5 minutes, held for 1 minute.
• Relaxation readings start after 6 minutes.
• No overstressing allowed.

Key Formula for Initial Stress:

[ \sigma_i = 0.7 \times \frac{P_{min}}{A_n} ]

• (P_{min}) = Minimum specified breaking load
• (A_n) = Nominal cross-sectional area of the strand

This ensures quality control and conformance per IS 6006 standards.

IS 6006: Delivery, Inspection and Testing Facilities - Key Points

1. Delivery & Inspection (Clauses 8.3, 9.1, 9.4)

• Sampling: If ≥10% of selected coils fail, the entire parcel is rejected (Clause 8.3).
• Inspection: General supply, inspection, and testing follow IS:1387-1967 (Clause 9.1).
• Manufacturer's Certificate: Must include:
  • Manufacturing process
  • Mechanical test results (including 0.2% proof load)
  • Chemical composition (if required)
  • Identification marks matching the material (Clause 9.4)

2. Testing Facilities & Specifications

IS 6006: Packing and Identification Marking - Key Points & Tables

1. Manufacturer's Certificate (Clause 9.4)

• Must include:
  • Process of manufacture
  • Mechanical test results (including 0.2% proof load)
  • Chemical composition (if required)
• Each test sheet must show the cast number or identification mark matching the material.

2. Packing & Marking (Clause 10)

• Each coil must be suitably marked.
• May carry the ISI Certification Mark.
• Test certificates must bear the Standard Mark if ISI mark is used.
• Marking ensures traceability and quality assurance under BIS.

3. Minimum Breaking Load & 0.2% Proof Load (Clause 6.2)

IS 6006: Workmanship and Finish, Size & Designation Summary

1. Workmanship and Finish (Clause 3.5)

• Finished strands must have uniform diameter.
• Must be free from injurious flaws and imperfections.
• No oil or grease on strands.
• Slight rusting allowed if it does not cause visible pits.

2. Size, Tolerances & Mass (Clause 4.3, Table 2)

IS 6006 - Marking and Traceability (Clauses 10.2 & 9.4)

Key Requirements:

• Coil Marking: Each coil of strands must be marked for traceability to the cast.
• Label Details:
  • Size of strand
  • Coil number
  • Class (if applicable)
• Traceability: Manufacturer must enable purchaser/authorized representative to trace strands back to the cast.
• Manufacturer’s Certificate: Must include manufacturing process, mechanical test results (including 0.2% proof load), chemical composition (if required), and cast identification.

Physical & Mechanical Properties (Clause 6.2 - Minimum Breaking Load & 0.2% Proof Load)

Relaxation Requirements as per IS 6006

Key Specifications (Clause 6.4 & 6.4.1)

• Relaxation stress after 1000 h ≤ 5% of initial stress (measured per 7.4).
• If 1000 h test not possible, 100 h test allowed if:
  • Relaxation at 100 h ≤ 3.5% of initial stress.
  • Manufacturer provides correlation proof between 100 h and 1000 h relaxation values.

Initial Stress for Relaxation Test (Clause 7.4)

• Initial stress = 70% of specified minimum tensile strength.

• Tensile strength calculated from:

  [ \text{Min Tensile Strength} = \frac{\text{Minimum Breaking Load}}{\text{Nominal Cross-sectional Area}} ]

• Temperature during test: 20 ± 2°C.

• Load applied over 5 minutes, held for 1 minute, then relaxation readings start after 6 minutes.

Minimum Breaking Loads (Clause 6.2 - Table Summary)

Summary Formula for Relaxation Stress Limit:

[ \sigma_r \leq 0.05 \times \sigma_i \quad \text{(after 1000 h)} ]

or

[ \sigma_r \leq 0.035 \times \sigma_i \quad \text{(after 100 h with proof)} ]

where:

• (\sigma_r) = relaxation stress,
• (\sigma_i) = initial applied stress (70% of min tensile strength).

flowchart LR
    A[Start Test] --> B[Apply Load over 5

IS 6006: Proof Load and Elongation Tests Summary

Proof Load Test (Clause 1.0 & 6.2)

• Load is applied until 1.0% extension is recorded on the extensometer.
• The applied load at this extension must be ≥ 0.2% proof load from Table 3.

Key Formulas:

• Proof Load (P₀.₂): Load causing 0.2% permanent strain.
• Extension at proof load = 1.0% strain.

Minimum Loads from Table 3 (N):

Procedure:

1. Attach extensometer to strand.
2. Increase load gradually.
3. Stop when extension = 1.0%.
4. Verify load ≥ 0.2% proof load from table.

flowchart TD
    A[Start Test] --> B[Attach Extensometer]
    B --> C[Apply Load Gradually]
    C --> D{Extension = 1.0%?}
    D -- No --> C
    D -- Yes --> E[Record Load]
    E --> F{Load ≥ 0.2% Proof Load?}
    F -- Yes --> G[Pass Test]
    F

IS 6006: Quality Control and Certification Key Points

1. Dimensions, Tolerances & Mass (Clause 4.3, Table 2)

2. Mechanical Properties (Clause 6.2, Tables 3 & 5)

3. Manufacturer's Certificate (Clause 9.4)

• Must include:
  • Manufacturing process details.
  • Test sheet with mechanical test results (breaking load, 0.