Methods of Test for Determination of Strength Properties of Natural Building Stones, Part II: Transverse Strength

IS 1121 Part 2 — Scope & Key Specifications

The standard covers the determination of transverse strength of materials (e.g., wood, plywood).

Key Points from Clauses:

• Clause 4.1:

  • Test specimen size: 200 mm × 50 mm × 50 mm
  • Apparatus as per Fig. 1 (with bearers 'A' and 'B') for 3-point bending test.

• Clause 6.6 & 6.7:

  • Test piece size and shape must be clearly specified.
  • Detailed description of specimen preparation is mandatory.

Typical Test Setup (Fig. 1 Summary):

• Specimen placed on two bearers (supports) spaced apart.
• Load applied at mid-span to measure transverse strength.

Transverse Strength Formula:

[ \sigma = \frac{3PL}{2bd^2} ]

Where:

• ( \sigma ) = transverse strength (N/mm²)
• ( P ) = load at failure (N)
• ( L ) = span length between supports (mm)
• ( b ) = specimen width (mm)
• ( d ) = specimen depth (thickness) (mm)

Summary Table:

flowchart LR
    A[Test Specimen 200x50x50 mm]
    B[Placed on Bearers A & B]
    C[Load applied at mid-span]
    D[Measure load at failure P]
    E[Calculate transverse strength σ]

    A --> B --> C --> D --> E

This scope ensures uniformity in transverse strength testing per IS 1121 Part 2.

IS 1121 (Part 2) - Selection of Samples for Transverse Strength Testing

Key Specifications:

• Clause 2.1:
  Samples must represent the true average quality of the stone type or grade.

• Clause 2.2:
  Samples are taken either from quarried stone or natural rock (see 2.2.1 & 2.2.2).

  • Size must be adequate to prepare the required number of test pieces.

• Clause 2.3:
  If quality variations exist, select multiple samples to cover the range of properties.

Practical Guidelines:

Notes:

• Ensure samples are free from defects like cracks or weathering.
• Follow standard conditioning before testing (Clause 3).

flowchart TD
  A[Select Stone Type/Grade] --> B[Check Quality Variation]
  B -- No Variation --> C[Select Representative Sample]
  B -- Variation Present --> D[Select Multiple Samples]
  C --> E[Prepare Test Pieces]
  D --> E
  E --> F[Condition Samples]
  F --> G[Test for Transverse Strength]

This approach ensures statistically valid and representative testing per IS 1121 (Part 2).

IS 1121 Part 2: Test Pieces and Conditioning Summary

• Sample Selection (Clause 2.3):
  Select multiple samples to capture property variations when rock quality varies perceptibly.

• Number of Test Pieces (Clause 3.3):
  Use 3 test pieces for each condition (e.g., saturated and dry).

• Drying Condition (Clause 3.3.2):

  • Dry test pieces in an oven at 105 ± 5°C for 24 hours.
  • Cool in a desiccator to room temperature (20–30°C) before testing.

• Test Piece Size & Shape (Clause 6.6):
  Must be clearly specified and consistent; typical cylindrical specimens are used.

Typical Conditioning Procedure

Notes:

• Conditioning ensures consistent moisture content for reliable strength tests.
• Dimensions affect test results; always report specimen size and shape.

flowchart TD
    A[Select Samples] --> B[Prepare 3 Test Pieces per Condition]
    B --> C[Conditioning]
    C --> D1[Oven Dry at 105±5°C for 24h]
    C --> D2[Cool in Desiccator to 20-30°C]
    D2 --> E[Test]

This ensures uniformity and comparability of test results per IS 1121 Part 2.

IS 1121 Part 2: Test Procedure for Transverse Strength

Key Specifications:

• Specimen size: 200 mm (length) × 50 mm (width) × 50 mm (thickness).
• Bearers: Diameter 40 mm; length > specimen width.
• Load application: Central, uniform rate of 200 kg/min.
• Load applied via: Third bearer (E), 40 mm diameter, placed midway between supports on the specimen's upper surface, parallel to supports.

Test Setup (Fig. 1):

• Two bearers (A and B) support the specimen at ends.
• Load applied centrally on bearer E.

Test Pieces:

• Number: 3 specimens per condition (dry, wet, etc.).

Evaluation:

• Record load at failure.
• Calculate transverse strength using:

[ \sigma = \frac{3PL}{2bd^2} ]

Where:

• ( \sigma ) = transverse strength (N/mm²)
• ( P ) = load at failure (N)
• ( L ) = span between supports (mm)
• ( b ) = specimen width (mm)
• ( d ) = specimen thickness (mm)

Summary Table:

flowchart LR
    A[Support Bearer A] --- S[Specimen (200x50x50)] --- B[Support Bearer B]
    E[Load Bearer E (40 mm)] -->|Load applied centrally| S

This ensures uniform bending and accurate transverse strength measurement as per IS 1121 Part 2.

IS 1121 Part 2: Loading and Measurement Key Points

Apparatus Setup (Clause 4.1 & 5.1)

• Specimen size: 200 × 50 × 50 mm
• Bearers A & B: Diameter 4 cm, spaced 15 cm apart (center to center).
• Load application bearer (E): Diameter 4 cm, placed midway between supports on specimen's upper surface.
• Bearers exceed specimen width to ensure uniform load distribution.
• Bearers supported on hardened steel balls for self-alignment.

Loading Rate (Clause 5.2)

• Load applied centrally at a uniform rate of 200 kg/min through bearer E.

Transverse Strength Calculation (Clause 6.1)

[ R = \frac{W \times L}{b \times d^2} ]

Where:

• ( R ) = transverse strength (kg/cm²)
• ( W ) = breaking load (kg)
• ( L ) = span length between bearers (cm) = 15 cm
• ( b ) = average width of specimen at midsection (cm)
• ( d ) = average depth of specimen at midsection (cm)

Summary Table

graph LR
A[Bearer A (4 cm dia)] ---|15 cm| B[Bearer B (4 cm dia)]
E[Load Bearer E (4 cm dia)] -->|Load 200 kg/min| S[Specimen (200x50x50 mm)]
S --> A
S --> B

This setup ensures accurate measurement of transverse strength per IS 1121 Part 2.

IS 1121 Part 2: Evaluation and Report of Test Results

Key Specifications (Clause 6)

• Test Piece Details (6.6):

  • Report the size and shape of the specimen tested.

• Preparation Description (6.7):

  • Include a detailed description of how the test pieces were prepared.

• Load Application (5.2):

  • Load applied centrally at a uniform rate of 200 kg/min through a third bearer (4 cm diameter) placed midway between supports.
  • Bearers must exceed specimen width.

• Rounding Off (0.3):

  • Final values should be rounded as per IS 2-1960.

Typical Reporting Format

Formula for Transverse Strength (Flexural Strength)

[ \sigma = \frac{3PL}{2bd^2} ]

Where:

• ( \sigma ) = Transverse strength (kg/cm² or MPa)
• ( P ) = Load at failure (kg)
• ( L ) = Span length between supports (cm)
• ( b ) = Width of specimen (cm)
• ( d ) = Thickness of specimen (cm)

Summary Diagram of Load Setup

graph LR
A[Support] --- S[Specimen]
S --- B[Support]
E[Load Bearer (4 cm dia)] -->|Load 200 kg/min| S

This ensures clarity and uniformity in evaluating and reporting transverse strength tests per IS 1121 Part 2.