Methods of Test for Autoclaved Cellular Concrete Products, Part IV: Corrosion Protection of Steel Reinforcement in Autoclave Cellular Concrete

IS 6441 Part 4 - Foreword Summary

This standard is part of a comprehensive set for Autoclaved Cellular Concrete (ACC) products, divided into nine parts for specific test methods:

Key points:

• Part IV specifically deals with corrosion protection of steel reinforcement embedded in ACC.
• The standard aligns with international practices while addressing Indian field conditions.
• Published by BIS in 1972, it ensures uniform testing and quality control.

No direct formulas or tables are in the Foreword; details appear in respective parts.

IS 6441 Part 4: Scope and Key Specifications

• Scope: Covers corrosion protection of steel reinforcement in autoclaved cellular concrete.
• Test Specimens:
  • Size: 40 × 40 × 150 mm prisms.
  • Steel bar positioned centrally.
  • Ends (40 × 40 mm faces) coated with moisture/vapour barrier (cold asphalt or bitumen emulsion + melted asphalt).
• Climatic Cabinet Conditions (Clause 3.1):
  • Relative Humidity: 90 ± 5%
  • Temperature cycles every 3 hours between 25 ± 5°C and 55 ± 5°C
  • Warming-up period: 1 hour per temperature
• Standard Parts Overview (Clause 0.4):

Diagram: Test Specimen Setup

graph LR
A[Steel Bar] --> B[Centered in 40x40x150 mm Prism]
B --> C[Ends Coated with Moisture Barrier]

This ensures uniform testing for corrosion protection under controlled moisture and temperature cycling.

IS 6441 Part 4: Sampling and Preparation of Test Specimens

Key Specifications:

• Test Specimen Size:

  • Prism: 40 × 40 × 150 mm
  • Steel bar centrally positioned inside the prism (Clause 2.2)

• Reference Specimens:

  • Three test specimens + three reference specimens per sample
  • Reference specimens cut adjacent to test specimens from the same bar (Clause 2.3)
  • Concrete and protective coating removed from reference specimens for visual inspection (Fig. 1)

• End Face Treatment:

  • End faces (40 × 40 mm) coated with moisture and vapor barrier (cold asphalt or bitumen emulsion + melted asphalt) (Clause 2.2)

• Climatic Conditions for Testing:

  • Exposure in climatic cabinet with:
    • Relative humidity: 90 ± 5%
    • Temperature cycling every 3 hours between 25 ± 5°C and 55 ± 5°C
    • 1-hour warming-up period for each temperature (Clause 3.1)

Summary Table:

Diagram: Specimen and Reference Specimen Setup

graph LR
  A[Test Specimen (40x40x150 mm)] --> B[Steel Bar (Central)]
  A --> C[End faces coated with bitumen]
  D[Reference Specimen] --> E[Cut adjacent to test specimen]
  E --> F[Concrete & coating removed for inspection]

This preparation ensures uniformity and reliable corrosion protection testing of steel reinforcement in autoclaved cellular concrete per IS 6441 Part 4.

IS 6441 Part 4 (1972) – Testing Equipment and Specimen Details for Corrosion Protection of Steel Reinforcement

Key Specifications:

• Test Specimens:

  • Size: 40 × 40 × 150 mm prism
  • Steel bar positioned centrally
  • End faces coated with moisture & vapor barrier (cold asphalt/bitumen + melted asphalt)

• Reference Specimens:

  • Same size and adjacent position on the same reinforcement bar as test specimens
  • Concrete and protective coating removed for visual inspection

• Climatic Cabinet Conditions (Clause 3.1):

  • Relative Humidity: 90 ± 5%
  • Temperature cycling every 3 hours between:
    • 25 ± 5°C and 55 ± 5°C
  • Warming-up period: 1 hour for each temperature change

Summary Table: Test Specimen Dimensions

Testing Environment Cycle

gantt
    title Temperature Cycling for Test Specimens
    dateFormat  HH:mm
    axisFormat  %H:%M

    section Cycle (3h)
    25°C ±5°C       :active, 00:00, 01:30
    Warming-up (55°C): 01:30, 01:00
    55°C ±5°C       :active, 02:30, 01:30
    Warming-up (25°C): 04:00, 01:00

This ensures accelerated corrosion testing under controlled humidity and temperature cycling for evaluating steel reinforcement protection in autoclaved cellular concrete.

IS 6441 Part 4 (1972) – Inspection & Assessment of Corrosion

Key Specifications for Corrosion Assessment (Clause 4.3)

• Visual Inspection: Rotate the test specimen bars along their length to check the entire surface.
• Rust Evaluation:
  • Bars free from rust or showing only slight rust (no flakes) uniformly distributed.
  • Rust should not cover more than 5% of the bar surface.
• If above conditions are met, the rust protecting agent is satisfactory.

Climatic Conditioning (Clause 3.1)

• Use a climatic cabinet with:
  • Relative humidity: 90 ± 5%
  • Temperature cycling every 3 hours between 25 ± 5°C and 55 ± 5°C
  • Warming-up period: 1 hour for each temperature change.

Reference Specimens

• Use reference bars with concrete and protective coating removed for comparison.
• Dimensions and specimen details as per Fig. I (not shown here).

Summary Table for Rust Assessment

flowchart LR
    A[Start Inspection] --> B{Rotate Bar Fully}
    B --> C[Check Rust Coverage]
    C --> D{Rust ≤ 5% and No Flakes?}
    D -->|Yes| E[Satisfactory Protection]
    D -->|No| F[Unsatisfactory Protection]

This ensures reliable evaluation of corrosion protection on steel reinforcement in autoclaved cellular concrete.

IS 6441 Part 4: Reporting of Test Results - Key Points

• Rounding Off Results:
  Final test values (observed or calculated) must be rounded as per IS 2:1960 (Rules for rounding numerical values).

• Reference Samples:

  • For each test specimen, prepare a reference specimen of identical size, cut from the same reinforcement bar, adjacent to the test specimen (see Fig. 1).
  • There must be 3 test specimens + 3 corresponding reference specimens.
  • Remove concrete and protective coating from reference specimens to visually inspect and classify steel bar surface condition.

• Testing Environment:
  Use a climatic cabinet maintaining:

  • Relative humidity: 90 ± 5%
  • Temperature cycling every 3 hours between 25 ± 5℃ and 55 ± 5℃, with a 1-hour warming period for each temperature.

Summary Table: Test Specimens & Reference Specimens

Rounding Rule Example (IS 2:1960)

flowchart LR
    A[Test Specimen] --> B[Reference Specimen]
    B --> C[Remove Concrete & Coating]
    C --> D[Visual Inspection & Classification]
    A --> E[Testing in Climatic Cabinet]
    E --> F[Report Results (Rounded per IS 2:1960)]

For detailed specimen dimensions and setup, refer to Fig. 1 of IS 6441 Part 4.