Method of Test for Toughness of Natural Building Stones

IS 5218: Scope & Key Specifications for Toughness Test of Natural Building Stones

Scope (Clause 1.1):
The standard covers the method of testing the toughness of natural building stones by impact. Toughness indicates resistance to failure under impact, critical for stones used in flooring, steps, warehouses, etc.

Key Equipment Specifications (Clause 1.1):

Additional Notes:

• Multiple samples should be tested if stone quality varies (Clause 2.4).
• The test measures energy absorption under impact, reflecting stone's toughness.
• Results should be rounded as per IS:2-1960.

Conceptual Diagram of Test Setup:

graph TD
    Hammer -->|Falls freely| Plunger
    Plunger -->|Contacts| Specimen
    Specimen -->|Placed on| Anvil
    Anvil -->|Fixed on| Foundation

This setup ensures consistent impact testing for stone toughness per IS 5218.

IS 5218: Sampling of Stones - Key Points & Specifications

• Sample Selection (Clauses 2.1 to 2.4):

  • Samples must represent a true average of the stone type/grade.
  • For quarried stone (2.2): Inspect ledge/quarry face for strata variations in colour & structure.
  • Obtain separate samples (~25 kg each) from all unweathered strata showing differences.
  • Exclude blasted/damaged pieces.
  • For field stones & boulders (2.3): Inspect deposits, record stone types & conditions, select separate samples for each class.
  • If quality varies perceptibly (2.4), select multiple samples to cover the range.

• Sample Weight: Minimum 25 kg per sample of unweathered stone.

• Purpose: Ensure samples reflect variability for accurate testing.

Summary Table of Sampling Requirements

flowchart TD
    A[Inspect Stone Deposit] --> B{Variations in Colour/Structure?}
    B -- Yes --> C[Select Separate Samples (≥25 kg each)]
    B -- No --> D[Select Representative Sample]
    C --> E[Exclude Damaged/Blasted Pieces]
    D --> F[Sample for Testing]
    E --> F

This ensures representative, unweathered, undamaged samples for reliable testing per IS 5218.

IS 5218: Test Specimens for Rock Strength

• Specimen Dimensions (Clause 3.1):

  • Cylinder length = 25 mm
  • Diameter = 25 mm

• Sample Selection (Clause 2.4):

  • Multiple samples required if rock quality varies perceptibly to capture property range.

• Specimen Preparation (Clause 3.4):

  • Cut using core drills or methods avoiding incipient fractures.
  • No hammer chipping or breaking.
  • Ends ground flat with water and carborundum/emery on cast iron lap to final size.

• Test Set (Clause 3.2):

  • Each test set = 3 specimens

Summary Table:

flowchart TD
    A[Sample Selection] --> B{Quality Variation?}
    B -- Yes --> C[Select Multiple Samples]
    B -- No --> D[Select Representative Sample]
    C & D --> E[Cut Specimens (Core Drill)]
    E --> F[Grind Ends Flat]
    F --> G[Prepare 3 Specimens per Test Set]

This ensures uniformity and reliability in rock strength testing per IS 5218.

IS 5218: Toughness Testing Machine Key Points

1. Machine Requirements (Appendix A, Clause 4.1)

• The toughness testing machine must conform to specifications ensuring consistent impact energy delivery.
• It typically involves a pendulum-type impact tester.
• The machine should allow precise measurement of the height of the blow (pendulum drop height).

2. Test Procedure (Clause 6)

• Toughness = Height of blow at failure (Clause 6.1).
• For specimens with structural weaknesses (seams, fissures), record each specimen's toughness and average toughness of the set (Clause 6.2, 6.4).

3. Key Formula

[ \text{Toughness} = h_f ]

• ( h_f ) = Height of pendulum at failure (m or cm)

4. Notes on Specimens (Clause 6.4)

• Any defects (seams, fissures) must be noted as they affect toughness results.

Summary Table: Toughness Testing Machine Parameters

flowchart LR
    A[Start Test] --> B[Place Specimen]
    B --> C[Release Pendulum]
    C --> D[Measure Height of Blow at Failure]
    D --> E[Record Toughness = Height]
    E --> F{Check for Defects?}
    F -->|Yes| G[Note Defects & Report]
    F -->|No| H[Report Results]

This ensures consistent, comparable toughness values per IS 5218.

IS 5218: Test Procedure for Toughness Testing

Key Points from Clauses:

• Test Set:

  • 3 specimens per test set (Clause 3.2).

• Specimen Condition:

  • Note any defects (seams, fissures) affecting results (Clause 6.4).

• Testing Machine Setup (Appendix A, Clause 5.1):

  • Specimen held securely without lateral support.
  • The specimen’s upper surface center must be tangential to the plunger’s spherical end at the lowest point.
  • Hammer drop heights:
    • 1 cm for 1st blow
    • 2 cm for 2nd blow
    • Increase by 1 cm for each subsequent blow until failure.

Test Procedure Summary:

Reporting (Clause 6):

• Include test results, specimen conditions, and any peculiarities.

flowchart LR
    A[Prepare 3 Specimens] --> B[Secure Specimen in Anvil]
    B --> C[Hammer Drop: 1 cm]
    C --> D{Specimen Failed?}
    D -- No --> E[Increase Hammer Drop by 1 cm]
    E --> C
    D -- Yes --> F[Record Results & Defects]

This ensures consistent toughness testing as per IS 5218.

IS 5218 – Report of the Toughness Test

Key Specifications for Report (Clause 6):

• When a plane of structural weakness is apparent (Clause 6.2):

  • Report individual toughness of each of the 3 specimens.
  • Report the average toughness of the set.
  • Identify the plane of weakness clearly.

• When no plane of structural weakness is apparent (Clause 6.3):

  • Report individual toughness of the 3 specimens.
  • Report the average toughness.

• Note any peculiar conditions (Clause 6.4):

  • Record defects like seams, fissures, or other anomalies that may affect results.

Test Procedure Summary (Clause 5.1):

• Specimen held on anvil without lateral support.
• Hammer free fall increments:
  • 1 cm for 1st blow
  • 2 cm for 2nd blow
  • Increase by 1 cm for each subsequent blow until failure.

Typical Report Format:

Appendix A Reference:

• Machine must ensure:
  • Accurate free fall height control.
  • Spherical plunger contact as per Clause 5.1.
  • Proper specimen holding without lateral constraints.

flowchart TD
    A[Start Test] --> B[Place specimen on anvil]
    B --> C[Set hammer fall height]
    C --> D[Apply blow]
    D --> E{Specimen failed?}
    E -- No --> C[Increase fall height by 1 cm]
    E -- Yes --> F[Record toughness]
    F --> G[Repeat for 3 specimens]
    G --> H[Calculate average toughness]
    H --> I[Prepare report with remarks]
    I --> J[End]

This ensures compliance with IS 5218 for toughness testing and reporting.

IS 5218: Requirements for Toughness Testing Machine (Appendix A, Clause 4.1)

• The toughness testing machine must be a pendulum type impact tester, designed to measure energy absorbed by a specimen during fracture.
• It should have a calibrated scale to directly read the energy absorbed (in Joules or kg-m).
• The machine must ensure:
  • Consistent pendulum release height
  • Minimal friction losses
  • Proper clamping of the specimen to avoid slippage
• The blade or striker must conform to specified dimensions and hardness to ensure consistent impact.

Key Test Formula:

[ \text{Toughness} = h_b \times m \times g ] Where:

• ( h_b ) = height of the pendulum at failure (m)
• ( m ) = mass of pendulum (kg)
• ( g ) = acceleration due to gravity (9.81 m/s²)

Important Notes:

• Record any peculiarities (seams, fissures) as per Clause 6.4.
• Report individual and average toughness for specimens, especially if structural weaknesses are visible (Clause 6.2).

flowchart LR
    A[Pendulum Release Height] --> B[Strikes Specimen]
    B --> C[Specimen Fractures]
    C --> D[Energy Absorbed Measured]
    D --> E[Toughness = Height at Failure × Mass × g]

This setup ensures reliable toughness measurement as per IS 5218 standards.