high tensile steel bars used in prestressed concrete

IS 2090: Scope & Key Specifications

• Scope: Covers physical requirements and testing criteria for materials under the standard.

• Physical Requirements (Clause 8.3.4):
  For any physical property tested, the test results must satisfy:
  [ \text{Mean} + 0.6 \times \text{Range} \leq \text{Max Spec Limit} ] [ \text{Mean} - 0.6 \times \text{Range} \geq \text{Min Spec Limit} ]

• Definitions (Clause 2.0): Standard definitions apply to terms used in the code.

• Rounding Off (Clause 0.5):
  Test results must be rounded off as per IS 2-1960, maintaining the same number of significant figures as specified values.

• Modifications in Revision (Clause 0.3):

  • Young's modulus requirement deleted.
  • SI units adopted.
  • Updated references to Indian Standards.

Summary Table for Physical Requirement Check

This ensures test results are statistically within acceptable tolerance limits.

flowchart LR
    A[Test Results] --> B{Calculate Mean & Range}
    B --> C[Check: Mean + 0.6 × Range ≤ Max Limit]
    B --> D[Check: Mean - 0.6 × Range ≥ Min Limit]
    C & D --> E{Both Conditions Satisfied?}
    E -->|Yes| F[Material Passes Physical Requirements]
    E -->|No| G[Material Fails Physical Requirements]

This approach ensures consistent quality control per IS 2090.

IS 2090: Key Definitions & Specifications

• Clause 2.0 (Definitions): Establishes the terminology used throughout the standard for clarity and uniform interpretation.

• Clause 8.3.4 (Physical Requirements Testing):
  For each characteristic tested, the mean and range must satisfy:
  [ \begin{cases} \text{Mean} + 0.6 \times \text{Range} \leq \text{Max Specification Limit} \ \text{Mean} - 0.6 \times \text{Range} \geq \text{Min Specification Limit} \end{cases} ]

• Clause 0.3 (Revisions):

  • Young's modulus requirement removed.
  • S.I. units adopted for physical properties.
  • Updated references to other Indian Standards.

• Clause 0.5 (Rounding Off):
  Final test values must be rounded as per IS 2-1960, retaining the same number of significant digits as the specified values.

Summary Table: Physical Test Compliance Check

This ensures test results are statistically within tolerance limits.

flowchart TD
    A[Test Results] --> B{Calculate Mean & Range}
    B --> C[Check: Mean + 0.6 × Range ≤ Max Limit]
    B --> D[Check: Mean - 0.6 × Range ≥ Min Limit]
    C & D --> E{Pass/Fail}

This approach ensures consistent quality control in materials as per IS 2090.

IS 2090: Manufacture and Chemical Composition - Key Points

Manufacture (Clause 3.2)

• Finished bars must be cleanly hot rolled to specified dimensions.
• Bars shall be sound, free from splits, harmful surface flaws, jagged edges, or defects.
• No excessive rust or foreign matter that can impair concrete adhesion.
• Agreement between purchaser and manufacturer can modify these requirements.

Chemical Composition (Clauses 3.1.1, 8.2.2, 8.3.3)

• Chemical analysis is mandatory on samples from bars in each lot.
• Limits on Phosphorus (P) and Sulphur (S) content must comply with IS 2090:1983.
• Typical maximum limits (approximate, check latest IS 2090 for exact values):
  • Phosphorus (P): ≤ 0.045%
  • Sulphur (S): ≤ 0.050%
• Methods for chemical analysis conform to relevant IS standards (second revision), ensuring accuracy.

Tensile Strength (Clause 2.6)

[ \text{Tensile Strength} = \frac{\text{Maximum Load}}{\text{Original Cross-sectional Area}} ]

Summary Table: Chemical Limits for IS 2090 Bars

flowchart TD
    A[Raw Steel] --> B[Hot Rolling]
    B --> C[Finished Bars]
    C --> D[Visual Inspection]
    C --> E[Chemical Analysis]
    E --> F{P & S within limits?}
    F -- Yes --> G[Approved for Use]
    F -- No --> H[Rejected or Reprocessed]

Note: Always refer to the latest IS 2090 edition for precise chemical limits and testing methods.

IS 2090: Mechanical Properties of Steel Bars

Key Specifications (Clause 8.1 & 6.1)

• Tensile Strength (Mis):
  Minimum tensile strength shall be not less than 80% of the specified minimum tensile strength.

• Mechanical Properties (Table 1):
  Includes Tensile Strength, Proof Stress, and Elongation values determined per Clause 7.2.2.

Statistical Acceptance Criteria (Clause 8.3.4)

For physical properties (except proof stress), test results must satisfy:

[ \text{(Mean + 0.6 × Range)} \leq \text{Maximum Specified Limit} ] [ \text{(Mean - 0.6 × Range)} \geq \text{Minimum Specified Limit} ]

This ensures consistency and reliability in mechanical properties.

Typical Table 1 Format (Example)

(Refer to IS 2090 Table 1 for exact values per grade)

Summary

• Tensile strength ≥ 80% of specified minimum.
• Proof stress and elongation per Table 1.
• Statistical check: Mean ± 0.6 × Range within limits.
• Young's modulus requirement removed in latest revision.
• S.I. units adopted throughout.

flowchart LR
    A[Mechanical Properties Testing] --> B[Tensile Strength]
    A --> C[Proof Stress]
    A --> D[Elongation]
    B --> E{Check ≥ 80% Specified Min}
    C --> F{Statistical Check}
    D --> F
    F --> G[(Mean + 0.6 × Range) ≤ Max Limit]
    F --> H[(Mean - 0.6 × Range) ≥ Min Limit]

This ensures reliable steel bar quality per IS 2090.

IS 2090: Dimensions and Tolerances Summary

1. Nominal Size Tolerances (Clause 5.1)

• Other tolerances can be mutually agreed (Clause 5.3).

2. Physical Requirements (Clause 8.3.4)

For physical test results (except proof stress), the following must hold:

[ \text{Mean} + 0.6 \times \text{Range} \leq \text{Max Specification Limit} ]

[ \text{Mean} - 0.6 \times \text{Range} \geq \text{Min Specification Limit} ]

Where:

• Mean = average of test results
• Range = difference between max and min test results

3. Additional Notes

• Young's modulus requirement removed.
• SI units are used throughout.
• Proof stress and relaxation tests have updated provisions.

flowchart LR
    A[Nominal Size] -->|Tolerance ±0.5 mm| B[Bars ≤ 25 mm]
    A -->|Tolerance ±0.6 mm| C[Bars > 25 mm]
    D[Physical Test Results] --> E{Check Limits}
    E -->|Mean + 0.6*Range ≤ Max| F[Pass Upper Limit]
    E -->|Mean - 0.6*Range ≥ Min| G[Pass Lower Limit]

This ensures dimensional accuracy and consistent physical properties per IS 2090.

IS 2090: Tensile Strength, Proof Stress & Elongation

Key Definitions (Clause 2.6)

• Tensile Strength (σt):
  [ \sigma_t = \frac{P_{max}}{A_0} ]
  where (P_{max}) = maximum load in tensile test, (A_0) = original cross-sectional area.

• Proof Stress:
  Stress at a specified permanent strain (usually 0.2% offset), indicating yield strength.

• Elongation:
  Percentage increase in gauge length after fracture.

Testing Method (Clause 7.2.2)

• Conduct tests per IS 1608:1972 for tensile strength, proof stress, and elongation.
• For cold-worked specimens, proof stress tests may be delayed beyond 48 hours.

Table 1 (Typical Values) - As per IS 2090 (Example)

(Exact values depend on grade and manufacturing process; refer to Table 1 in IS 2090 for specifics.)

Summary:

• Use IS 1608 for test procedure.
• Calculate tensile strength using max load/original area.
• Proof stress is yield strength at specified offset.
• Elongation is % increase in length after fracture.
• Values vary by grade; check Table 1 in IS 2090.

flowchart LR
  A[Tensile Test Specimen] --> B[Apply Load]
  B --> C{Load reaches max?}
  C -- No --> B
  C -- Yes --> D[Record Pmax]
  D --> E[Calculate Tensile Strength = Pmax/A0]
  D --> F[Determine Proof Stress at 0.2% offset]
  D --> G[Measure Elongation after fracture]

IS 2090: Sampling and Testing Procedures - Key Points

1. Sampling Size (Clause 8.1.2, Table 2)

• Sample size: Number of bars selected randomly from the lot.
• Sub-sample size: Number of bars taken from the sample for detailed testing.

2. Criteria for Conformity (Clause 8.3.2, Table 8.3)

• Maximum allowable bars failing tests without rejecting the lot.

3. Test Specimen Selection (Clause 7.1)

• Test specimens are selected from sub-samples as per the above sizes.

4. Constant Strain Relaxation Test (Clause 7.3)

• Initial stress: 70% of specified minimum tensile strength.
• Temperature: 20 ± 2°C.
• Load applied within 5 minutes, held constant for 1 minute.
• Relaxation readings start after 6 minutes.
• Number of specimens tested as agreed with purchaser.

flowchart TD
    A[Lot of Bars] --> B[Select Sample Size (Table 2)]
    B --> C[Select Sub-Sample]
    C --> D[Test Specimens]
    D --> E{Test Results}
    E -->|Failures ≤ Permissible| F[Lot Accepted]
    E -->|Failures > Permissible| G[Lot Rejected]

This ensures statistically valid sampling and testing for quality control per

IS 2090: Relaxation Test Key Points

1. Test Procedure (Clause 7.3)

• Initial stress = 70% of specified minimum tensile strength.
• Load applied within 5 minutes, held constant for 1 minute.
• Load readings start from the end of 6th minute.
• Temperature maintained at 20 ± 2℃.
• No load adjustments after initial application.
• Number of specimens as agreed with purchaser.

2. Relaxation Limit (Clause 6.2)

• Stress relaxation after 1000 hours must not exceed 49 N/mm².

3. Summary Table

4. Important Notes

• Test bars must not be overstressed.
• Manufacturer must provide test records or proof of compliance.
• Sampling as per purchaser-manufacturer agreement.

sequenceDiagram
    participant Tester
    participant Specimen
    Tester->>Specimen: Apply load (70% tensile strength) within 5 min
    Specimen-->>Tester: Hold load constant for 1 min
    Note right of Specimen: No load changes after this
    Specimen-->>Tester: Start relaxation readings after 6 min
    Note right of Specimen: Maintain 20 ± 2 ℃ temperature
    Specimen-->>Tester: Measure relaxation up to 1000 hrs (max 49 N/mm²)

This ensures the bar's stress relaxation performance meets IS 2090 requirements.

IS 2090: Delivery, Inspection & Testing Facilities - Key Points

1. General Requirements (Clause 9.1):

   • Inspection, testing, and supply of materials must conform to IS 1387-1967.
   • Manufacturer must provide mill records with bar details (size, marks, cast number) before specimen selection (Clause 7.1.2).

2. Proof Stress (Clause 8.3.5):

   • All test specimens must meet characteristic proof stress requirements.

3. Identification & Marking (Clause 10.1.1):

   • Each bar or bundle must be marked with size, grade, and optionally the Standard Mark.
   • The Standard Mark ensures compliance with BIS quality control and continuous surveillance.

4. Inspection & Testing Facilities:

   • Facilities should enable:
     • Verification of physical and mechanical properties.
     • Sampling as per IS 1387.
     • Traceability via mill records and marking.

Summary Table: Inspection & Testing Requirements

flowchart LR
    A[Manufacturer] --> B[Provide Mill Records]
    B --> C[Sampling per IS 1387]
    C --> D[Test Specimens]
    D -->|Proof Stress| E[Pass/Fail]
    E --> F{Pass?}
    F -->|Yes| G[Mark Bars with Standard Mark]
    F -->|No| H[Reject Batch]

References:

• IS 2090 Clause 9, 10
• IS 1387-1967 (General testing & inspection)
• BIS Standard Mark guidelines

IS 2090: Certification and Marking Key Points

Certification

• Clause 9.2: No dispatch without purchaser’s certification or ISI Mark on bundles/coils.
• Clause 9.4: If no inspection at manufacturer’s works, a certificate with:
  • Manufacturing process details
  • Mechanical test results (each test sheet with identification mark)
  • Chemical composition (if required)

Marking

• Clause 10.1.1: Each bar or metal tag on bundles must carry the Standard Mark (ISI Mark).
• The Standard Mark ensures compliance with BIS inspection, testing, and quality control.
• Use of the Standard Mark is governed by the Bureau of Indian Standards Act, 1936.

Physical Test Results (Clause 8.3.4)

For physical properties (except proof stress), test results must satisfy:

[ \begin{cases} \text{Mean} + 0.6 \times \text{Range} \leq \text{Max Spec Limit} \ \text{Mean} - 0.6 \times \text{Range} \geq \text{Min Spec Limit} \end{cases} ]

Summary Table

flowchart TD
    A[Manufacture] --> B{Inspection at Works?}
    B -- Yes --> C[Certification by Purchaser]
    B -- No --> D[Manufacturer's Certificate]
    C & D --> E[Marking with ISI Standard Mark]
    E --> F[Dispatch Approved]

This ensures traceability, quality, and conformity per IS 2090.