high tensile steel bars used in prestressed concrete
1983 Edition

IS 2090: Extent and Principal Specifications

• Scope: Details the physical property requirements and evaluation criteria applicable to prestressing steel bars.

• Physical Property Criteria (Clause 8.3.4):
  Test outcomes must satisfy the statistical conditions below:
  [ \text{Mean} + 0.6 \times \text{Range} \leq \text{Maximum Limit Specified} ] [ \text{Mean} - 0.6 \times \text{Range} \geq \text{Minimum Limit Specified} ]

• Terminology (Clause 2.0): Establishes definitions for key terms used within the standard.

• Rounding Protocol (Clause 0.5): Test results are rounded following IS 2-1960, maintaining the precision consistent with the specified values.

• Revision Highlights (Clause 0.3):

  • Removal of Young's modulus requirement.
  • Adoption of SI units.
  • Updated references to current Indian Standards.

Physical Requirement Compliance Summary

This approach ensures test results fall within statistically acceptable ranges.

flowchart LR
    A[Test Data] --> B{Calculate Mean & Range}
    B --> C[Validate: Mean + 0.6 × Range ≤ Max Limit]
    B --> D[Validate: Mean - 0.6 × Range ≥ Min Limit]
    C & D --> E{Are Both Conditions Met?}
    E -->|Yes| F[Material Meets Physical Criteria]
    E -->|No| G[Material Fails Physical Criteria]

This statistical evaluation promotes consistent quality control as per IS 2090.

IS 2090: Definitions and Clarifications

• Clause 2.0: Provides clear explanations of terminology to ensure uniform understanding throughout the standard.

• Clause 8.3.4: Specifies the statistical acceptance criteria for physical properties, requiring:

[ \begin{cases} \text{Mean} + 0.6 \times \text{Range} \leq \text{Maximum Limit} \ \text{Mean} - 0.6 \times \text{Range} \geq \text{Minimum Limit} \end{cases} ]

• Clause 0.3: Revision details include the elimination of Young's modulus as a requirement and the use of SI units.

• Clause 0.5: Mandates rounding of test data in accordance with IS 2-1960, preserving significant figures consistent with specified values.

Physical Test Compliance Summary

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

This ensures material physical properties conform reliably to IS 2090 standards.

IS 2090: Manufacturing and Chemical Specifications

Production Requirements (Clause 3.2)

• Bars must be hot rolled with a clean finish to the designated size.
• Steel bars should be intact, free from splits, significant surface defects, jagged edges, or any damage.
• Excessive corrosion or contaminants that could reduce bond strength with concrete are not permitted.
• Modifications to these requirements can be agreed upon between the purchaser and manufacturer.

Chemical Analysis (Clauses 3.1.1, 8.2.2, 8.3.3)

• Chemical tests are compulsory on samples taken from each batch.
• Limits for Phosphorus and Sulfur content must meet IS 2090 specifications.
• Typical maximum concentrations (consult latest IS 2090 for exact limits):
  • Phosphorus (P): ≤ 0.045%
  • Sulfur (S): ≤ 0.050%
• Chemical testing procedures conform to relevant IS standards ensuring accurate analysis.

Tensile Strength Formula (Clause 2.6)

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

Chemical Limits Summary

flowchart TD
    A[Raw Steel Input] --> B[Hot Rolling Process]
    B --> C[Finished Steel Bars]
    C --> D[Visual Examination]
    C --> E[Chemical Testing]
    E --> F{Are P & S Within Limits?}
    F -- Yes --> G[Approved for Construction Use]
    F -- No --> H[Rejected or Reprocessed]

Refer to the most recent edition of IS 2090 for exact chemical composition requirements.

Mechanical Properties Specified in IS 2090

Primary Specifications (Clauses 8.1 & 6.1)

• Minimum Tensile Strength:
  The actual tensile strength must not be less than 80% of the specified minimum tensile strength.

• Mechanical Parameters (Table 1):
  Includes tensile strength, proof stress, and elongation as per Clause 7.2.2.

Statistical Acceptance (Clause 8.3.4)

Test results for physical attributes (excluding proof stress) must meet the following:

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

This ensures reliable and consistent mechanical performance.

Example Table 1: Mechanical Property Values

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

Summary

• Tensile strength must be ≥ 80% of designated minimum.
• Proof stress and elongation values as per standard Table 1.
• Statistical validation of test data required.
• Young’s modulus requirement removed in latest revisions.
• SI units used for all measurements.

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

This framework guarantees dependable quality of prestressing steel bars.

IS 2090: Dimensional Standards and Tolerances

1. Nominal Diameter Tolerances (Clause 5.1)

• Other tolerance limits may be established by mutual agreement (Clause 5.3).

2. Physical Property Compliance (Clause 8.3.4)

For physical tests except proof stress, the following must be true:

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

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

Where:

• Mean = average of test results
• Range = difference between highest and lowest test results

3. Additional Details

• Requirement for Young’s modulus has been removed.
• SI units are applied consistently.
• Updated procedures exist for proof stress and relaxation testing.

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

Ensures bars meet dimensional and physical property requirements.

IS 2090: Guidelines for Tensile, Proof Stress, and Elongation Testing

Definitions (Clause 2.6)

• Tensile Strength (σt):
  [ \sigma_t = \frac{P_{max}}{A_0} ] Where (P_{max}) is the maximum load during tensile testing and (A_0) is the original cross-sectional area.

• Proof Stress:
  The stress corresponding to a predefined permanent strain (commonly at 0.2% offset), representing yield strength.

• Elongation:
  The percentage increase in gauge length measured after fracture.

Testing Procedure (Clause 7.2.2)

• Tests are performed in accordance with IS 1608:1972.
• For cold-worked specimens, proof stress testing may be deferred beyond 48 hours.

Typical Values (Table 1 Examples)

(Consult IS 2090 Table 1 for exact grade-specific data.)

Summary

• Utilize IS 1608 for test methodology.
• Calculate tensile strength as maximum load divided by original area.
• Proof stress is the yield point determined at the specified offset.
• Elongation is the post-fracture elongation percentage.
• Refer to Table 1 for precise values based on steel grade.

flowchart LR
  A[Specimen Preparation] --> B[Apply Tensile Load]
  B --> C{Reached Maximum Load?}
  C -- No --> B
  C -- Yes --> D[Record Maximum Load]
  D --> E[Compute Tensile Strength = Pmax/A0]
  D --> F[Determine Proof Stress at 0.2% Offset]
  D --> G[Measure Elongation After Break]

IS 2090: Sampling and Testing Guidelines

1. Sampling Quantities (Clause 8.1.2, Table 2)

• Sample size refers to bars randomly selected from the lot.
• Sub-sample size denotes bars taken from the sample for detailed testing.

2. Acceptance Criteria (Clause 8.3.2, Table 8.3)

• Specifies the highest number of defective bars allowed without rejecting the entire batch.

3. Specimen Selection (Clause 7.1)

• Test specimens are taken from the defined sub-samples.

4. Constant Strain Relaxation Test (Clause 7.3)

• Initial stress set at 70% of specified minimum tensile strength.
• Temperature maintained at 20 ± 2°C.
• Load applied within 5 minutes and held steady for 1 minute.
• Relaxation measurement begins after 6 minutes.
• Number of specimens tested agreed upon by purchaser and supplier.

flowchart TD
    A[Bar Lot] --> B[Select Sample per Table 2]
    B --> C[Choose Sub-Sample]
    C --> D[Prepare Test Specimens]
    D --> E{Analyze Test Outcomes}
    E -->|Within Failure Limits| F[Accept Lot]
    E -->|Exceeds Failure Limits| G[Reject Lot]

This procedure assures statistically valid testing and quality evaluation.

IS 2090: Key Aspects of Relaxation Testing

1. Testing Methodology (Clause 7.3)

• Initial applied stress: 70% of specified minimum tensile strength.
• Load application must be completed within 5 minutes and maintained for 1 minute.
• Relaxation readings begin after the 6th minute.
• Temperature controlled at 20 ± 2°C.
• No adjustments to load after initial application.
• Number of specimens tested is based on purchaser-manufacturer agreement.

2. Relaxation Limits (Clause 6.2)

• After 1000 hours, stress relaxation must not exceed 49 N/mm².

3. Summary Table

4. Important Considerations

• Bars must not be subjected to excessive stress.
• Test documentation or proof of compliance must be provided by the manufacturer.
• Sampling is conducted per mutual agreement.

sequenceDiagram
    participant Tester
    participant Specimen
    Tester->>Specimen: Apply load (70% tensile strength) within 5 minutes
    Specimen-->>Tester: Maintain load for 1 minute
    Note right of Specimen: Load remains constant post application
    Specimen-->>Tester: Begin relaxation readings after 6 minutes
    Note right of Specimen: Temperature controlled at 20 ± 2 °C
    Specimen-->>Tester: Measure relaxation up to 1000 hours (limit 49 N/mm²)

This ensures compliance with IS 2090 relaxation performance criteria.

IS 2090: Guidelines for Delivery, Inspection, and Testing

1. General Provisions (Clause 9.1):

   • Inspections, testing, and material supply must comply with IS 1387-1967.
   • Manufacturers must provide mill certificates detailing bar size, markings, and cast numbers prior to sample selection (Clause 7.1.2).

2. Proof Stress Requirements (Clause 8.3.5):

   • All tested specimens must fulfill the specified proof stress values.

3. Marking and Identification (Clause 10.1.1):

   • Each individual bar or bundle must bear markings indicating size, grade, and optionally the BIS Standard Mark.
   • The Standard Mark signifies adherence to BIS quality assurance and ongoing surveillance.

4. Inspection and Testing Infrastructure:

   • Facilities should support:
     • Verification of mechanical and physical properties.
     • Sampling consistent with IS 1387.
     • Traceability through mill records and marking.

Summary of Inspection and Testing Criteria

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

References:

• IS 2090 Clauses 9 and 10
• IS 1387-1967 (General Testing and Inspection)
• BIS Standard Mark Regulations

IS 2090: Certification and Marking Essentials

Certification

• Clause 9.2: Bars must not be dispatched without purchaser approval or the presence of the ISI mark on bundles or coils.
• Clause 9.4: If no inspection occurs at the manufacturer’s premises, a certificate must accompany the shipment containing:
  • Details of the manufacturing process.
  • Mechanical test results with test sheet identification.
  • Chemical composition data if required.

Marking

• Clause 10.1.1: Each bar or bundle must bear the BIS Standard Mark (ISI Mark).
• The Standard Mark confirms compliance with BIS inspection, testing, and quality control measures.
• The use of the Standard Mark is regulated under the Bureau of Indian Standards Act, 1936.

Physical Property Test Compliance (Clause 8.3.4)

Results for physical properties (excluding proof stress) must meet:

[ \begin{cases} \text{Mean} + 0.6 \times \text{Range} \leq \text{Maximum Limit} \ \text{Mean} - 0.6 \times \text{Range} \geq \text{Minimum Limit} \end{cases} ]

Summary Table

flowchart TD
    A[Manufacture Process] --> 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 Approval]

This ensures traceability, quality assurance, and compliance with IS 2090.