Methods of Test for Autoclaved Cellular Concrete Products, Part IV: Corrosion Protection of Steel Reinforcement in Autoclave Cellular Concrete
1972 Edition

Overview of IS 6441 Part 4

This document is part of a series addressing testing methodologies for Autoclaved Cellular Concrete (ACC) products, segmented into nine distinct parts:

Highlights:

• Part IV specifically concerns corrosion protection of reinforcing steel embedded in ACC.
• The standard harmonizes with global methodologies while catering to Indian environmental conditions.
• Published by the Bureau of Indian Standards in 1972, it establishes consistent testing and quality protocols.

No formulas or tables are included in this introductory section; detailed procedures are found in subsequent parts.

Scope of IS 6441 Part 4

• Objective: To define test methods for evaluating corrosion protection of steel reinforcement within autoclaved cellular concrete.
• Test Specimen Specifications:
  • Prism dimensions: 40 mm × 40 mm × 150 mm.
  • Reinforcement bar centrally embedded.
  • Prism end faces (40 mm × 40 mm) sealed with moisture and vapor barriers (using cold asphalt or bitumen emulsion coated with melted asphalt).
• Environmental Conditioning (Clause 3.1):
  • Relative Humidity maintained at 90 ± 5%.
  • Temperature cycling every 3 hours between 25 ± 5°C and 55 ± 5°C.
  • Each temperature phase includes a 1-hour warming period.
• Related Parts in the Series (Clause 0.4):

Diagram: Test Specimen Configuration

graph LR
A[Steel Reinforcement Bar] --> B[Placed Centrally in 40x40x150 mm Prism]
B --> C[Ends Sealed with Moisture Barrier]

This setup ensures consistent evaluation of corrosion resistance under controlled moisture and temperature cycles.

Sampling and Preparation Guidelines per IS 6441 Part 4

Key Details:

• Specimen Dimensions:

  • Prism size: 40 mm × 40 mm × 150 mm.
  • Reinforcing steel bar positioned at the geometric center (Clause 2.2).

• Reference Specimens:

  • For each batch, prepare three test specimens and three reference specimens.
  • Reference specimens are cut adjacent to test samples from the same reinforcement bar (Clause 2.3).
  • Concrete and protective coatings are completely removed from the reference bars to permit visual corrosion inspection (see Fig. 1).

• End Face Treatment:

  • Prism faces of 40 mm × 40 mm are coated with moisture and vapor barriers using cold asphalt or bitumen emulsion combined with melted asphalt (Clause 2.2).

• Environmental Exposure Conditions:

  • Specimens are conditioned in a 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 at each temperature stage (Clause 3.1).

Summary Table:

Diagram: Test and Reference Specimen Layout

graph LR
  A[Test Specimen (40x40x150 mm)] --> B[Steel Bar Positioned Centrally]
  A --> C[End Faces Coated with Bitumen]
  D[Reference Specimen] --> E[Cut Adjacent to Test Specimen]
  E --> F[Concrete and Coating Removed for Inspection]

This method guarantees uniform specimen preparation for reliable corrosion protection assessment.

Equipment and Specimen Details under IS 6441 Part 4 (1972)

Specifications:

• Test Specimens:

  • Prism dimensions: 40 × 40 × 150 mm.
  • Reinforcing bar placed centrally within the prism.
  • End faces sealed with moisture and vapor barriers (cold asphalt or bitumen emulsion plus melted asphalt).

• Reference Specimens:

  • Identical size and adjacent location on the same reinforcing bar as test specimens.
  • Coatings and concrete are removed to allow direct visual inspection.

• Climatic Cabinet Settings (Clause 3.1):

  • Relative Humidity: 90 ± 5%.
  • Temperature cycles every 3 hours between:
    • 25 ± 5°C and 55 ± 5°C.
  • Each temperature step includes a 1-hour warm-up period.

Specimen Dimensions Summary:

Temperature Cycling Schedule

gantt
    title Temperature Cycling Protocol
    dateFormat  HH:mm
    axisFormat  %H:%M

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

This accelerated test environment simulates corrosion-inducing conditions under controlled humidity and temperature cycling.

Inspection and Assessment Procedures for Corrosion (IS 6441 Part 4, 1972)

Corrosion Evaluation Criteria (Clause 4.3):

• Visual Inspection: Rotate the reinforcement bars along their longitudinal axis to inspect the entire steel surface.
• Rust Condition:
  • Bars must be free of rust or exhibit only minor, uniformly distributed rust without any flaking.
  • Rust coverage should not exceed 5% of the bar surface.
• If these conditions are met, the rust-inhibiting treatment is considered effective.

Environmental Conditioning (Clause 3.1):

• Use a climatic cabinet maintaining:
  • Relative humidity at 90 ± 5%.
  • Temperature cycling every 3 hours between 25 ± 5°C and 55 ± 5°C.
  • 1-hour warm-up intervals for each temperature.

Reference Bars:

• Remove concrete and protective coatings from reference specimens to establish baseline corrosion levels.
• Specimen dimensions and details are provided in the standard's Figure I.

Rust Assessment Summary:

flowchart LR
    A[Begin Inspection] --> B{Rotate Bar Fully}
    B --> C[Evaluate Rust Coverage]
    C --> D{Rust ≤ 5% and No Flaking?}
    D -- Yes --> E[Protection Considered Adequate]
    D -- No --> F[Protection Considered Inadequate]

This evaluation process ensures trustworthy assessment of corrosion resistance in steel reinforcement embedded within ACC.

Guidelines for Test Result Reporting under IS 6441 Part 4

• Rounding Protocol:

  • Final numerical results, whether observed or computed, should be rounded following the stipulations of IS 2:1960 which governs numerical rounding rules.

• Reference Specimens:

  • For each test specimen, a corresponding reference specimen of identical size is prepared from an adjacent section of the same reinforcement bar (refer to Fig. 1).
  • A set includes three test and three reference specimens.
  • Concrete and coatings are removed from reference specimens to facilitate visual inspection and classification.

• Testing Environment:

  • Testing is conducted in a climatic cabinet with:
    • Relative humidity at 90 ± 5%.
    • Temperature cycling every 3 hours between 25 ± 5°C and 55 ± 5°C.
    • Each temperature phase preceded by a 1-hour warm-up period.

Summary Table: Specimen Details

Rounding Rules per IS 2:1960

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

Refer to Figure 1 in IS 6441 Part 4 for detailed specimen dimensions and preparation.