structural granite
1974 Edition

Scope Overview - Key Specifications & Sampling (Clause 6)

Scope: The standard applies to granite blocks and slabs with defined dimensional and physical property requirements.

Sampling & Testing Protocol (Clause 6)

• General & Dimensional Checks: All samples inspected; lots exceeding permissible defectives are rejected.
• Physical Tests: Selected sub-samples evaluated for compressive strength, water absorption, and specific gravity.
• Lot Acceptance: Lot is approved only if no sub-sample fails the physical tests.

Notes:

• Sampling is conducted randomly.
• Numerical results are rounded to the significant figures specified by the standard.
• Refer to Clause 3 of the standard for detailed physical testing methods.

flowchart TD
    A[Receive Lot] --> B[Determine Sample Size (Table)]
    B --> C[Inspect Dimensions & General Criteria]
    C -->|Defectives ≤ Allowed| D[Choose Sub-sample]
    C -->|Defectives > Allowed| E[Reject Lot]
    D --> F[Perform Compressive Strength Test]
    F --> G[Conduct Water Absorption & Specific Gravity Tests]
    G -->|All Pass| H[Accept Lot]
    G -->|Any Fail| E[Reject Lot]

For comprehensive test procedure details, consult Clause 6 and associated sections.

General Specifications for Structural Granite

Essential Requirements (Clause 2 & 6)

• Granite Quality (2.1):

  • Must be devoid of defects such as cracks, harmful veins, or cavities.
  • Should exhibit no imperfections that could compromise strength or appearance.

• Sampling & Testing (6.3, 6.4):

  • Random sampling conducted based on Table 1 (sample sizes and defect limits).
  • Examination includes:
    • Dimensions adherence
    • Visual and general quality checks
  • Physical testing on sub-samples includes:
    • Compressive strength
    • Water absorption
    • Specific gravity

• Lot Acceptance:

  • Lot is accepted if defective units do not exceed permissible limits.
  • All physical tests on sub-samples must pass.

Sampling Table Summary

Relevant Testing Equations

• Water Absorption (%)
  [ Water Absorption = \frac{Weight_{saturated} - Weight_{dry}}{Weight_{dry}} \times 100 ]

• Specific Gravity
  [ Specific Gravity = \frac{Weight_{dry}}{Weight_{dry} - Weight_{suspended}} ]

• Compressive Strength: Conducted as per applicable standard methods; minimum values vary by granite grade.

flowchart TD
    A[Granite Lot] --> B[Inspect Dimensions & Quality]
    B -->|Pass| C[Choose Sub-sample]
    C --> D[Test Compressive Strength]
    D --> E[Test Water Absorption & Specific Gravity]
    E --> F{Any Failures?}
    F -->|No| G[Approve Lot]
    F -->|Yes| H[Reject Lot]
    B -->|Fail| H

Summary: The granite must be free from structural defects and undergo random sampling for quality assurance.

Strength Requirements for Structural Granite

Critical Requirements:

• Compressive Strength: The granite must have a minimum compressive strength of 1000 kg/cm² in accordance with IS 1121-1974 (Clause 3.1).
• Granite must lack flaws, harmful veins, or cavities that could undermine structural performance (Clause 2.1).

Sampling & Testing (Clause 6.4):

• Random sub-samples are selected as per Table 1.
• Physical tests performed include:
  • Compressive strength
  • Water absorption
  • Specific gravity
• The lot is accepted only if all samples meet these criteria.

Summary Table of Strength Parameters:

Additional Notes:

• Ensure granite quality per Clause 2.1 for reliability.
• Test order: Compression → Water Absorption → Specific Gravity on identical samples.

flowchart TD
    A[Lot Selection] --> B[Dimension & Quality Check]
    B -->|Satisfactory| C[Random Sub-sample Selection]
    C --> D[Compression Testing (IS 1121)]
    D --> E[Water Absorption Testing]
    E --> F[Specific Gravity Testing]
    F --> G{Test Failures?}
    G -->|Yes| H[Reject Lot]
    G -->|No| I[Approve Lot]

This procedure guarantees structural granite meets the durability and strength standards.

Dimensional Requirements and Tolerances

1. Block Dimensions & Allowances (Clause 4.2)

• Facing blocks: ±5 mm tolerance
• Edges: Dressed following IS 1129-1972 specifications

2. Slab Dimensions & Allowances (Clause 4.1.1)

• Shapes allowed: Rectangular or square
• Length & breadth tolerance: ±2 mm
• Thickness tolerance: ±1 mm
• Bottom surface may be rough
• Top surface must be finely dressed
• Joint faces dressed square with the top surface for a minimum of 50 mm without hollowness or spalling

3. Numerical Rounding

• Round values to the same number of significant digits as the standard specifies (per IS 2-1960).

4. Testing and Sampling (Clause 6.4)

• Sub-sample size per Table 1
• Tests performed include compressive strength, water absorption, and specific gravity
• The lot is accepted if all tests pass

Dimensional Tolerances Table

Visual Summary:

flowchart TD
    A[Blocks] -->|±5 mm Tolerance| B[Dimensions Checked]
    C[Slabs] -->|±2 mm Length/Breadth| D[Dimensions Checked]
    C -->|±1 mm Thickness| E[Thickness Checked]
    D --> F[Top Surface: Fine Dressed]
    E --> F
    F --> G[Joint Faces Dressed Back 50 mm]

This summarizes the critical dimensional and tolerance requirements for structural granite blocks and slabs.

Marking Protocols for Granite Blocks and Slabs

• Manufacturer’s Identification (Clause 5.1): Each block or slab type must bear the manufacturer’s mark or initials to ensure traceability.

• ISI Certification Mark (Clause 5.1.1): Use of the ISI mark is optional and regulated by the Indian Standards Institution Certification Mark Act, indicating compliance with quality assurance and ongoing inspection.

Marking Summary Table

Sampling and Testing Related to Marking

• As per Clause 6.4, a sub-sample is randomly selected from the lot for physical tests:

  • Compressive strength
  • Water absorption
  • Specific gravity

• The lot is approved only if all sub-samples pass these tests.

Marking and Quality Assurance Process Flow

flowchart TD
    A[Produce Blocks/Slabs] --> B[Apply Manufacturer's ID Mark]
    B --> C{Apply ISI Mark?}
    C -- Yes --> D[Add ISI Certification Mark]
    C -- No --> E[Proceed Without ISI Mark]
    D & E --> F[Random Sampling per Clause 6.4]
    F --> G[Compressive Strength Test]
    F --> H[Water Absorption Test]
    F --> I[Specific Gravity Test]
    G & H & I --> J{Any Test Failures?}
    J -- No --> K[Accept Lot]
    J -- Yes --> L[Reject Lot]

Marking ensures product traceability and quality verification in accordance with the standard.

Sampling and Testing Guidelines for Granite Blocks and Slabs

Sampling Details (Clause 6.2 & Table 1)

• Sample size is determined by the lot size.
• Random selection methods (e.g., random number tables as per IS 4905-1968) are employed.
• The number of defective units in the sample should not exceed permissible limits.

Testing Requirements (Clause 6.3 & 6.4)

• All sampled units are checked for dimensions and general quality.
• Selected sub-samples undergo tests for:
  • Compressive strength
  • Water absorption
  • Specific gravity
• The lot is accepted only if no sub-sample unit fails.

Process Flow

flowchart TD
    A[Select Lot] --> B[Random Sampling per Table 1]
    B --> C[Dimension and General Quality Check]
    C -->|Defectives ≤ Allowed| D[Choose Sub-sample]
    D --> E[Compressive Strength Test]
    E --> F[Water Absorption & Specific Gravity Tests]
    F -->|All Pass| G[Approve Lot]
    C -->|Defectives > Allowed| H[Reject Lot]
    F -->|Any Fail| H

References:

• IS 3316 Clauses 6.2 to 6.4
• IS 4905-1968 for random sampling techniques

This protocol assures quality control through statistical validation before approval.

Lot Acceptance Guidelines

Sampling and Approval (Clause 6.2 - 6.4)

• Sampling: Random selection of blocks/slabs based on sample size.
• Inspection: All samples evaluated for general and dimensional standards.
• Defective Units: Lot accepted if defective units are within permitted limits.
• Physical Testing: Sub-samples undergo compressive strength, water absorption, and specific gravity tests.
• Final Acceptance: No sub-sample may fail physical tests.

Important Notes:

• Defective units are those failing general or dimensional criteria.
• Physical tests are sequentially performed on the same sub-samples.
• Sampling must follow random selection methods.

flowchart TD
    A[Lot of Blocks/Slabs] --> B[Select Sample (Per Table 1)]
    B --> C[Inspect General & Dimensional Criteria]
    C -->|Defectives ≤ Allowed| D[Approve Lot]
    C -->|Defectives > Allowed| E[Reject Lot]
    D --> F[Select Sub-sample for Physical Tests]
    F --> G[Compressive Strength Test]
    G --> H[Water Absorption & Specific Gravity Tests]
    H -->|All Pass| I[Confirm Lot Acceptance]
    H -->|Any Fail| E

This framework ensures compliance with quality standards for granite units.

Physical Properties of Structural Granite

• Sampling (Clause 6.4):

  • Randomly select sub-samples per Table 1 after dimension checks.
  • Perform tests on sub-samples including:
    • Compressive strength
    • Water absorption
    • Specific gravity (per IS 1122-1974)

• Acceptance Conditions: No failures allowed in any physical property tests.

• Specific Gravity Requirement (Clause 3.2): Minimum specific gravity of 2.6.

• General Quality (Clause 2.1): Granite must be free from cracks, veins, cavities affecting strength or aesthetics.

Test Methods and Criteria Summary

Testing Workflow

flowchart TD
    A[Select Granite Lot] --> B[Dimension & Quality Inspection]
    B --> C[Random Sub-sample Selection]
    C --> D[Compressive Strength Test]
    D --> E[Water Absorption Test]
    E --> F[Specific Gravity Test]
    F --> G{Any Test Failure?}
    G -- No --> H[Approve Granite Lot]
    G -- Yes --> I[Reject Granite Lot]

For detailed sampling sizes, consult Table 1 of the standard; for specific gravity test procedures, refer to IS 1122.

Surface Dressing Requirements for Structural Granite

Dimensional and Finishing Specifications (Clauses 4.1.1 & 4.2)

• Slabs: Rectangular or square shape
  • Length & breadth tolerance: ±2 mm
  • Thickness tolerance: ±1 mm
• Surface Finish:
  • Top face: finely dressed, free from hollowness or spalling
  • Bottom face: rough finish permitted
  • Joint faces: must be dressed back square with the top surface for at least 50 mm
• Blocks for Masonry:
  • Dimension tolerance: ±5 mm for facing blocks
  • Edges dressed as per IS 1129-1972

Rounding of Numerical Values

• Follow IS 2-1960 for rounding, maintaining the number of significant digits as specified.

Applicable Testing Standards

• True Specific Gravity: IS 1124 (First revision)
• Water Absorption & Apparent Specific Gravity: IS 1125 (First revision)
• Dressing Recommendations: IS 1129 (First revision)

Dimension Tolerance Summary

flowchart LR
    A[Stone Slab] --> B[Top Surface: Fine Dressed]
    A --> C[Bottom Surface: Rough Permitted]
    A --> D[Joint Faces: Dressed Back 50 mm]
    E[Blocks] --> F[Edges Dressed per IS 1129]
    E --> G[Dimension Tolerance ±5 mm]

This ensures dimensional precision and quality surface finish essential for durable stone masonry.

Criteria for Rejecting Defective Granite

1. Defect-Free Requirement (Clause 2.1)

• Granite must be free from cracks, harmful veins, cavities, or imperfections.
• Such defects adversely affect the structural strength, durability, and appearance.
• Visual inspection must exclude:
  • Cracks or fissures
  • Weathered or soft areas
  • Cavities or voids
  • Stains or discolorations affecting longevity

2. Strength and Durability Requirements

• While the standard lacks detailed numerical tables, typical structural granite properties include:
  • Compressive strength ≥ 100 MPa
  • Water absorption ≤ 0.6%
  • Density approximately 2600–2800 kg/m³

3. Recommended Tests

• Compression test to verify minimum strength
• Flexural strength typically 10–15% of compressive strength
• Water absorption test to assess porosity and durability

Typical Properties Summary

flowchart TD
    A[Inspect Granite] --> B{Are Defects Present?}
    B -- Yes --> C[Reject Granite]
    B -- No --> D[Proceed to Strength Testing]
    D --> E{Meets Strength Criteria?}
    E -- No --> C
    E -- Yes --> F[Accept Granite for Structural Use]

Note: Refer to IS 1121 for testing procedures and IS 3316 for quality guidelines.