Methods of test for determination of strength properties of natural building stones, Part IV: Shear strength

IS 1121 Part 4 - Scope Summary

Scope:
IS 1121 Part 4 (1974) specifies the methods and apparatus for testing cement. It details the dimensions and assembly of test devices, particularly the Dutton Punching Shear Device used for evaluating cement properties.

Key Specifications from Clause 51.00

• Hole and Post Dimensions:

  • Holes: Ø 51.00 mm (slide fit with plunger)
  • Posts on lower member: 2 holes, slide fit with 24 mm Ø posts
  • Posts on upper member: 25 mm Ø posts slide fit with holes

• Test Piece:

  • Size and shape must be indicated per Clause 6.5 (typically cylindrical or prismatic specimens)

Important Notes:

• All dimensions are in millimeters.
• The device assembly involves two holes and posts ensuring precise alignment.
• The standard includes detailed figures (Fig. 2) for device parts and assembly.

Typical Test Piece Dimension (per general IS 1121 standards):

Summary Diagram of Dutton Punching Shear Device Assembly

graph LR
A[Upper Member] -->|25 mm Ø Posts| B[Lower Member]
B -->|24 mm Ø Posts| C[Test Piece]
A -->|51 mm Ø Holes| C

For detailed test procedures and full device drawings, refer to IS 1121 Part 4 (1974) official document.

IS 1121 (Part 4) – Selection of Sample for Shear Strength Testing of Natural Stones

Key Specifications:

• Clause 2.1: Sample must represent a true average of the stone type or grade.
• Clause 2.2: Sample should be taken from:
  • Quarried stone, or
  • Natural rock (see 2.2.1 & 2.2.2 for specifics).
• Sample size must be adequate to prepare the required number of test specimens.
• Clause 3.1: Test pieces must be prepared using saws only; chisels or hand tools are prohibited to avoid damage.

Important Notes:

• The sample size depends on the number of tests planned (usually minimum 3 specimens).
• Proper sampling ensures representative test results for shear strength.
• Numerical values for specimen dimensions and test procedures are detailed in other clauses of IS 1121 Part 4.

Summary Table for Sample Selection:

flowchart LR
    A[Select stone sample] --> B{Is stone quarried?}
    B -- Yes --> C[Take sample from quarry]
    B -- No --> D[Take sample from natural rock]
    C & D --> E[Ensure adequate size for test pieces]
    E --> F[Cut test pieces using saws only]
    F --> G[Prepare specimens for shear strength test]

This ensures accurate, reliable shear strength results per IS 1121 (Part 4).

IS 1121 Part 4: Test Pieces and Conditioning

Key Specifications:

• Sample Selection (Clause 2.3):
  Select multiple samples to cover variations in rock quality for property range determination.

• Test Piece Size & Shape (Clause 6.5):
  Must be clearly indicated before testing.

Conditioning Procedures:

Testing Directions:

• Perform separate tests with load parallel and perpendicular to the rift (3.6.1 & 3.6.2).

Summary Table:

flowchart LR
    A[Select Samples] --> B[Test Piece Size & Shape]
    B --> C{Conditioning}
    C --> D[Dry: Oven 105±5°C, 24h + Desiccator]
    C --> E[Saturated: Water immersion 20-30°C, 72h]
    D --> F[Test Load: Parallel & Perpendicular to Rift]
    E --> F

This ensures consistent, comparable results per IS 1121 Part 4.

IS 1121 Part 4 - Apparatus for Shear Tests

Key Apparatus:

• Modified Johnson Shear Tool (Fig. 1)
• Dutton Punching Shear Device (Fig. 2A & 2B)

Both are used with a standard testing machine of adequate capacity.

Dutton Punching Shear Device Specifications (Clause 51.00):

All dimensions are in millimeters.

Test Piece:

• Size and shape must be clearly indicated (Clause 6.5).

Summary Diagram (Apparatus Overview):

graph LR
    A[Testing Machine] --> B[Modified Johnson Shear Tool]
    A --> C[Dutton Punching Shear Device]
    C --> D[Plunger (51 mm Ø)]
    C --> E[Lower Member with 2 Holes (Slide Fit)]
    C --> F[Posts (24 & 25 mm Ø)]

Note: Use the apparatus as per the detailed figures and dimensions in IS 1121 Part 4 (1974) for accurate shear testing.

IS 1121 Part 4 — Test Procedure Summary

Test Piece Specifications (Clause 6.5)

• Test piece size and shape must be clearly indicated.
• Typical specimen size: 50 mm × 50 mm (see Fig. 1 & 2).

Test Setup (Clause 5.2)

• Use Dutton Punching Shear Device.
• Mark center lines on slab surface.
• Measure slab thickness at 3 points around a 50 mm diameter circle, accuracy ±0.2 mm.
• Center test piece between upper and lower plates; align plunger over test section.
• Load applied via testing machine at max speed 1 mm/min.
• Keep testing machine beam in floating position during loading.

Key Dimensions (from figures)

Test Execution

• Use 3 test pieces per test (Clause 3.6).
• Align device carefully; apply load gradually.
• Record load vs displacement until failure.

Diagram: Test Setup Overview

flowchart TD
    A[Test Piece 50x50 mm] --> B[Dutton Punching Shear Device]
    B --> C[Upper Plate with Plunger]
    B --> D[Lower Plate with Posts]
    C --> E[Load applied at 1 mm/min]
    D --> F[Specimen centered and supported]

This procedure ensures consistent evaluation of punching shear strength as per IS 1121 Part 4 (1974).

IS 1121 Part 4: Evaluation and Report of Test Results (Clause 6)

Key Points:

• Test Specimen Size & Shape (Clause 6.5): Must be clearly indicated in the report.
• Measurement Accuracy (Clause 5.2):
  • Thickness measured to nearest 0.2 mm at 3 equidistant points around a 50 mm circle at the center.
  • Test piece centered between plates of the punching device.
• Test Setup:
  • Use Dutton Punching Shear Device with specified hole/post dimensions (e.g., 51 mm Ø hole, 24-25 mm Ø posts).
  • Load applied at a speed ≤ 1 mm/min.
  • Testing machine beam kept floating during loading.
• Result Rounding: Follow IS 2-1960 for rounding final values.

Typical Evaluation Formula for Shear Strength (τ):

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

Where:

• (P) = Maximum load at failure (N)
• (A) = Shear area (mm²), depending on specimen geometry

Reporting Checklist:

• Specimen dimensions and shape
• Test device details (e.g., Dutton device)
• Load application rate and procedure
• Measured thickness and centering method
• Final shear strength value with rounding per IS 2-1960

flowchart TD
    A[Prepare Test Specimen] --> B[Measure Thickness @ 3 Points (±0.2 mm)]
    B --> C[Set up Dutton Punching Shear Device]
    C --> D[Center Specimen & Device in Testing Machine]
    D --> E[Apply Load @ ≤ 1 mm/min]
    E --> F[Record Max Load at Failure]
    F --> G[Calculate Shear Strength (τ = P/A)]
    G --> H[Round Off per IS 2-1960]
    H --> I[Prepare Test Report with Details]

For detailed dimensions of the punching device and posts, refer to Clause 51.00 and Fig. 2 of IS 1121 Part 4.