concrete masonry units, Part 3: Autoclaved cellular Aerated concrete blocks

IS 2185 Part 3 - Scope Summary

This part of IS 2185 covers concrete masonry units (blocks) with specifications on dimensions, density, and measurement methods.

Key Points:

• Scope: Defines standard requirements for concrete blocks used in masonry (Clause 2.0).
• Density: Mean density values must fall within limits of Table 1 (Clause 11.2).

Dimensions (Clause 8.2 & 4.1):

• Length: Checked at 4 positions per block.
• Height: Checked at 6 positions.
• Thickness: Measured at 7 positions.
• Measurements must comply with tolerances specified in Clause 3.2.3.

Table 1 (Density Range) - Typical Values:

Measurement Positions (Fig. 1):

graph LR
A[Block] --> B[Length: 4 points]
A --> C[Height: 6 points]
A --> D[Thickness: 7 points]

Summary: IS 2185 Part 3 standardizes block dimensions and density, ensuring quality and uniformity in masonry units.

IS 2185 Part 3 - Definitions & Key Specifications

1. Definitions (Clause 2.0)

• The standard defines terms related to Autoclaved Cellular Concrete (ACC) blocks, including density, compressive strength, and thermal conductivity.

2. Physical Properties (Clause 11.2, 11.3 & Table 1)

3. Block Density (Clause 8.3)

• Must comply with Table 1 values when tested per Clause 9.1 (oven-dry density test).

Summary:

• Density governs strength and thermal properties.
• Compressive strength varies by grade and density.
• Thermal conductivity increases with density.

This classification helps in selecting ACC blocks for structural and insulation requirements.

IS 2185 Part 3 (1984) — Dimensions and Tolerances for Concrete Blocks

1. Nominal Dimensions (Clause 3.2.1)

2. Measurement Positions (Clause 4.1)

• Length: Check at 4 positions on whole blocks and cut specimens.
• Height: Check at 6 positions on whole blocks.
• Thickness (Width): Check at 7 positions.

3. Definitions (Clause 2.8)

• Width: External dimension at bedding plane, perpendicular to length and height.

4. Tolerances (Clause 3.2.3)

• Tolerances apply as per measurement positions; exact values depend on block size (refer IS 2185 Part 3 Table 3.2.3 for detailed tolerance limits).

Summary Diagram of Measurement Positions

graph TB
    A[Block]
    A --> L[Length: 4 positions]
    A --> H[Height: 6 positions]
    A --> W[Thickness: 7 positions]

Note: Always refer to IS 2185 Part 3 Table 3.2.3 for specific tolerance values per dimension and block size.

IS 2185 Part 3 — Classification of Autoclaved Cellular Concrete Blocks

Key Specifications (Clause 11.3, Table 1)

Important Clauses:

• Clause 8.3: Block density must comply with Table 1 when tested as per 9.1.
• Clause 8.4: Minimum compressive strength is average of 12 units as per Table 1 and tested per 9.2.
• Clause 3.4: Blocks with special faces to be manufactured only if specified.

Summary:

• Blocks are classified by oven-dry density.
• Each density class has two grades of compressive strength.
• Thermal conductivity increases with density.
• Testing standards ensure quality and uniformity.

flowchart TD
    A[Block Classification] --> B[Density (kg/m³)]
    B --> C1[451-550]
    B --> C2[551-650]
    B --> C3[651-750]
    B --> C4[751-850]
    B --> C5[851-1000]
    C1 --> D1[Grade 1: 2.0 N/mm²]
    C1 --> D2[Grade 2: 1.5 N/mm²]
    C1 --> D3[0.21 W/m·K]
    %% Similar nodes for other classes omitted for brevity

This classification helps select blocks based on

IS 2185 Part 3 - Materials Key Specifications

Thermal Conductivity (Clause 8.5 & 11.4)

• Thermal conductivity must not exceed values in Table 1 when tested per Clause 9.3.
• Mean thermal conductivity ≤ specified value in Table 1.

Physical Properties of Autoclaved Cellular Concrete Blocks (Table 1, Clause 11.3)

Notes:

• Density is in oven-dry condition.
• Compressive strength is minimum required.
• Thermal conductivity is measured in air-dry condition.
• Values rounded as per IS 2-1969.

This table guides selection of blocks based on strength and insulation needs, ensuring compliance with IS 2185 Part 3.

IS 2185 (Part 3) - Manufacture of Autoclaved Cellular Concrete (ACC) Blocks

Key Specifications & Tables:

1. Manufacture (Clause 6.1, Appendix A)

• ACC blocks are manufactured by mixing cement, lime, sand, water, and aluminum powder.
• The mix is poured into molds and subjected to autoclaving (steam curing under pressure) to achieve desired strength and density.

2. Physical Properties (Clause 11.3, Table 1)

3. Compressive Strength (Clause 8.4)

• Minimum compressive strength is the average of 12 units tested as per Clause 9.2.
• Strength varies with density and grade as per Table 1.

4. Special Faces (Clause 3.4)

• Blocks with special faces (e.g., tongue & groove, chamfered) are manufactured if specified.

Summary:

• Density and strength are interrelated; higher density yields higher strength and thermal conductivity.
• Autoclaving is essential for strength development.
• Use Table 1 to select block grade based on structural and thermal requirements.

flowchart TD
    A[Raw Materials] --> B[Mixing]
    B --> C[Molding]
    C --> D[Autoclaving]
    D --> E[Testing for Strength & Density]
    E --> F[Classification by Table 1]
    F --> G[

IS 2185 Part 3 - Physical Requirements for Autoclaved Cellular Concrete Blocks

Key Specifications (from Table 1 & Clauses 8.3, 8.4, 11.2, 11.3):

Testing Methods:

• Density: Measured as per Clause 9.1.
• Compressive Strength: Average of 12 units tested per Clause 9.2.

Summary:

• Block density and compressive strength must conform to the above ranges.
• Thermal conductivity increases with density.
• Grade 1 blocks have higher strength than Grade 2 for the same density.

This ensures blocks meet structural and thermal performance criteria as per IS 2185 Part 3.

IS 2185 Part 3: Mechanical Properties Summary

Key Properties & Specifications

Notes:

• Compressive strength testing: Average of 12 units, grouped in 3 groups of 4 for range calculation.
• Thermal conductivity testing: Mean values must be within limits to ensure insulation performance.

Formula Recap:

[ \bar{X} - 0.6R > \text{Minimum compressive strength (Table 1)} ]

Where:

• ( \bar{X} ) = Mean compressive strength
• ( R ) = Average range of grouped test values

For exact values, refer to Table 1 of IS 2185 Part 3, which tabulates minimum compressive strength and max thermal conductivity for different block types.

IS 2185 Part 3: Test Methods Key Points

1. Compressive Strength (Clause 8.4 & 9.2)

• Tested on 12 units, average compressive strength must meet Table 1 values.

• Test as per Clause 9.2: Apply axial load until failure; record max load.

• Formula for compressive strength:

  [ f_c = \frac{P}{A} ]

  where:

  • ( f_c ) = compressive strength (N/mm²)
  • ( P ) = maximum load (N)
  • ( A ) = cross-sectional area (mm²)

2. Block Density (Clause 8.3 & 9.1)

• Density tested per Clause 9.1; mean density must be within limits of Table 1.

• Density formula:

  [ \rho = \frac{W}{V} ]

  where:

  • ( \rho ) = density (kg/m³)
  • ( W ) = weight of block (kg)
  • ( V ) = volume of block (m³)

3. Thermal Conductivity (Clause 8.5 & 9.3)

• Thermal conductivity tested as per Clause 9.3.
• Must not exceed values in Table 1.

Table 1: Typical Values (Excerpt)

flowchart TD
    A[Test Specimen] --> B[Measure Dimensions]
    B --> C[Calculate Volume]
    A --> D[Weigh Specimen]
    D --> E[Calculate Density]
    A --> F[Apply Compressive Load]
    F --> G[Record Max Load]
    G --> H[Calculate Compressive Strength]
    A --> I[Test Thermal Conductivity]
    I --> J[Compare with Max Allowed

IS 2185 Part 3: Sampling and Inspection Key Points

1. Sampling Tolerances (Clause 11.1)

• Maximum 2 blocks with dimensions outside tolerance or visible defects allowed in inspected samples.

2. Dimensional Checks (Clause 4.1)

• Length: Check at 4 positions on whole blocks and cut specimens.
• Height: Check at 6 positions on whole blocks.
• Thickness: Check at 7 positions.

Refer to Fig. 1 in IS 2185-3 for exact measurement locations.

3. Visual Inspection (Clause 8.1)

• Blocks must be sound, crack-free, and without defects affecting strength or placement.
• Minor chipping from handling is not grounds for rejection.

4. Sampling for Independent Tests (Clause 13.1)

• Samples for independent testing are taken before or immediately after delivery.
• Tests follow the standard specifications.

Summary Table for Dimensional Checks

flowchart TD
    A[Block Sampling] --> B{Check Dimensions}
    B --> C[Length - 4 positions]
    B --> D[Height - 6 positions]
    B --> E[Thickness - 7 positions]
    A --> F{Visual Inspection}
    F --> G[Sound, crack-free]
    F --> H[Minor chipping allowed]
    A --> I{Defect Tolerance}
    I --> J[Max 2 defective blocks allowed]
    A --> K{Independent Testing}
    K --> L[Sample before/after delivery]
    K --> M[Tests per IS 2185-3]

This ensures compliance with IS 2185 Part 3 sampling and inspection requirements.

IS 2185 Part 3: Compliance Criteria Summary

Key Compliance Parameters (Table 1 Reference)

Testing Sample Distribution (Clause 10.5.2)

• 24 blocks total per batch:
  • 12 for compressive strength
  • 3 for density
  • 3 for thermal conductivity
  • 3 for drying shrinkage
  • 3 reserved for drying shrinkage re-test

Compliance Criteria (Clause 11)

• Average compressive strength of 12 blocks must meet or exceed Table 1 values.
• Density and thermal conductivity must conform to Table 1 limits.
• Testing must follow prescribed methods (Clauses 9.1, 9.2, 9.3).

Typical Table 1 Extract (Example Values)

flowchart TD
    A[24 Blocks Sample] --> B[12 Blocks: Compressive Strength Test]
    A --> C[3 Blocks: Density Test]
    A --> D[3 Blocks: Thermal Conductivity Test]
    A --> E[3 Blocks: Drying Shrinkage Test]
    A --> F[3 Blocks: Drying Shrinkage Re-test (if needed)]

Summary: Compliance requires average strength, density, and thermal conductivity within limits of Table 1, tested per specified methods on designated sample sizes.

IS 2185 Part 3: Manufacturer’s Certificate (Clause 12)

• Purpose: Manufacturer must ensure masonry units conform to IS 2185 Part 3 specifications.
• Requirement: Upon request, a Manufacturer’s Certificate must be provided to the purchaser or representative confirming compliance.
• Certificate Content: Should affirm that units meet:
  • Dimensional tolerances
  • Compressive strength (see Table 1, Clause 8.4)
  • Drying shrinkage (Clause 11.5)
  • Other relevant physical and mechanical properties as per the code

Key Related Specifications

Summary Diagram of Manufacturer’s Responsibility

flowchart TD
    A[Manufacture Units] --> B[Quality Checks]
    B --> C{Conform to IS 2185 Part 3?}
    C -- Yes --> D[Issue Manufacturer's Certificate]
    C -- No --> E[Reprocess or Reject Units]
    D --> F[Supply Certificate to Purchaser]

Note: The certificate is a formal assurance, backed by test results, that the masonry units meet all IS 2185 Part 3 criteria.

IS 2185 Part 3: Independent Testing - Key Points

1. Number of Tests (Clause 10.5)

• Testing frequency and sample size should comply with the code to ensure statistical reliability.
• Typically, 12 units are tested for compressive strength (Clause 8.4).

2. Compressive Strength (Clause 8.4)

• Minimum compressive strength is the average of 12 units.
• Testing method: As per Clause 9.2.
• Values are specified in Table 1 (refer to IS 2185 Part 3 Table 1 for exact strengths based on block type and density).

3. Block Density (Clause 8.3)

• Density must meet requirements in Table 1.
• Testing method: As per Clause 9.1.

4. Manufacturer's Responsibility (Clause 12.1)

• Manufacturer must verify conformity to specifications.
• Must provide a certificate of compliance when requested.

Summary Table Extract (Example from Table 1)

flowchart TD
    A[Manufacturer] --> B[Tests: Density & Strength]
    B --> C{Test Results}
    C -->|Pass| D[Certificate of Compliance]
    C -->|Fail| E[Review & Reprocess]
    D --> F[Supply to Purchaser]

Note: Always refer to the latest IS 2185 Part 3 for detailed tables and test procedures.

Storage and Handling of Autoclaved Cellular Concrete Blocks (IS 2185 Part 3)

• General Storage Requirements:
  As per Clause 14.1, storage must follow IS 4082-1977 guidelines, ensuring blocks are kept dry, off the ground, and protected from weather to prevent moisture absorption and damage.

• Physical Properties (Clause 11.3, Table 1):

• Handling Tips:
  • Use mechanical aids to avoid block damage.
  • Stack blocks on a flat, firm base with wooden pallets or planks.
  • Limit stacking height to prevent crushing (usually max 1.5 m).
  • Protect from rain and moisture during storage.

Summary Diagram: Storage Setup

flowchart LR
    A[Ground] --> B[Wooden Planks/Pallets]
    B --> C[Stacked Blocks]
    C --> D[Protective Cover (Tarpaulin)]
    style C fill:#f9f,stroke:#333,stroke-width:2px

Note: Refer IS 4082-1977 for detailed storage specifications.

IS 2185 Part 3 – Marking of Concrete Masonry Units

Key Specifications (Clause 15.1 & 15.1.1)

Each lot of concrete masonry units must be marked with:

• Manufacturer Identification
• Grade and Block Density
• Month and Year of Manufacture

Additionally:

• The ISI Certification Mark may be included on each block, indicating compliance with Indian Standards and quality assurance.

Dimensional Checking (Clause 4.1 & Fig. 1)

• Length: Measured at 4 positions on whole blocks and cut specimens.
• Height: Measured at 6 positions on whole blocks.
• Thickness: Measured at 7 positions.

This ensures dimensional consistency and quality control.

Summary Table for Marking Requirements

flowchart TD
    A[Concrete Masonry Units] --> B[Marking]
    B --> C[Manufacturer ID]
    B --> D[Grade & Density]
    B --> E[Month & Year]
    B --> F[ISI Certification Mark (optional)]

Note: Use ISI mark only if licensed under Indian Standards Institution rules.