Methods of Test for Determination of Strength Properties of Natural Building Stones, Part III: Tensile Strength

IS 1121 (Part 3) : 2012 — Scope Summary

Scope:
This part of IS 1121 specifies methods for testing the tensile strength of natural building stones.

Key Points:

• Test Specimen: Size and shape must be clearly indicated (Clause 7.6).
• Units: All dimensions in millimeters (mm).
• Test Setup: Refer to Fig. 1 for general arrangement of tensile strength testing.
• Referenced Standards: The document refers to other relevant standards, which should be checked for the latest editions.

Typical Test Specimen Dimensions (Indicative from IS 1121 Part 3):

Tensile Strength Calculation:

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

• (f_t) = Tensile strength (N/mm² or MPa)
• (P) = Maximum load at failure (N)
• (A) = Cross-sectional area of specimen (mm²)

Testing Arrangement (Conceptual):

flowchart LR
    A[Stone Specimen] --> B[Testing Machine]
    B --> C[Load Application]
    C --> D[Measure Load at Failure]
    D --> E[Calculate Tensile Strength]

Note:

For detailed procedures, specimen preparation, and reporting, refer to the full IS 1121 (Part 3):2012 document. Always verify with the latest revision.

IS 1121 (Part 3): 2012 - References Summary

• Scope: Specifies methods for testing tensile strength of building stones.
• Test Specimen: Size and shape must be indicated; dimensions in millimeters (Clause 7.6).
• General Arrangement: Fig. 1 shows setup for tensile strength testing.
• Referenced Standards: The document references other BIS standards, subject to revision; users should check for latest editions.

Key Points:

Contact for BIS:

• Headquarters: Manak Bhavan, New Delhi
• Website: www.bis.org.in
• Regional Offices: Delhi, Kolkata, Chandigarh, Chennai, Mumbai

Typical Tensile Strength Test Setup (Fig. 1)

flowchart LR
    A[Stone Sample] --> B[Grips]
    B --> C[Tensile Testing Machine]
    C --> D[Load Application]
    D --> E[Measure Tensile Strength]

For detailed test procedures, specimen preparation, and reporting formats, refer to Clause 7 and Annexes of IS 1121 (Part 3): 2012.

IS 1121 Part 3 — Selection of Samples: Key Points

• Clause 3.1:
  Samples must represent the true average quality of the stone type or grade.

• Clause 3.2:
  Samples should be taken either from:

  • Quarried stone (3.2.1) or
  • Natural rock (3.2.2)

• Sample Size:
  Instead of a fixed minimum weight (previously 25 kg), the code now specifies "stones of adequate size" sufficient to prepare the required number of test specimens.

Practical Notes:

• Ensure sampling covers the variability in the stone deposit to avoid bias.
• The sample size must allow preparation of all test specimens as per test requirements (compression, tensile, etc.).
• No explicit formula or table is given for sample size; rely on test specimen dimensions and number for adequacy.

flowchart LR
    A[Stone Deposit] --> B[Sampling]
    B --> C{Sample Type}
    C -->|Quarried Stone| D[Select representative stones]
    C -->|Natural Rock| E[Extract representative samples]
    D & E --> F[Check sample size]
    F -->|Adequate| G[Prepare test specimens]
    F -->|Inadequate| H[Increase sample size]

Summary: Select representative, adequately sized samples from quarried or natural stone to prepare all required test specimens, ensuring true average properties are captured.

IS 1121 Part 3: Test Specimens and Conditioning Summary

Specimen Selection (Clause 3.3)

• Select multiple samples when rock quality varies to capture property range.

Specimen Conditioning (Clause 4.3.2)

• Dry specimens at 70 ± 5 ℃ for 48 hours.
• Cool in desiccator to 20–30 ℃.
• Achieve constant mass: two consecutive hourly weights differ by ≤ 0.1%.

Test Specimen Details (Clauses 4.3, 6.1)

• Use 5 specimens per test condition.
• Specimens sandwiched between steel plates:
  • Thickness: 10 mm
  • Width: ≥ 25 mm
  • Length: equal to specimen length
• Plates:
  • One with spherical seating (center aligned with plate face center)
  • Other plain rigid block
  • Plate flatness tolerance: ≤ 0.0125 mm
• Load applied at 200 N/s continuously until failure.
• Record max load with ±1% accuracy.

Testing Machine Requirements

• Adequate capacity, uniform load application.
• Steel bearing plates as above.

Summary Table for Specimen Conditioning

flowchart TD
    A[Rock Sample] --> B[Select multiple specimens]
    B --> C[Dry at 70±5℃ for 48h]
    C --> D[Cool to 20-30℃ in desiccator]
    D --> E[Check constant mass (≤0.1% difference)]
    E --> F[Sandwich specimen between steel plates]
    F --> G[Apply load at 200 N/s until failure]
    G --> H[Record max

IS 1121 Part 3: Apparatus Specifications for Testing

• Drying of Specimens:

  • Oven temperature: 70 ± 5 ℃
  • Duration: 48 hours
  • Cooling: In desiccator to 20–30 ℃ until constant mass
  • Constant mass criterion: Two consecutive hourly mass measurements differ by ≤ 0.1%

• Testing Machine Requirements:

  • Sufficient capacity for specified load and loading rate
  • Equipped with two steel bearing plates, thickness ≥ 10 mm with hardened faces
  • One plate: fitted with a spherically seated ball bearing (center aligned with plate center)
  • Other plate: plain rigid bearing block
  • Bearing face dimensions: width > 25 mm, length ≥ specimen length
  • Flatness tolerance of bearing faces: deviation ≤ 0.0125 mm
  • Movable spherical plate must freely rotate and tilt slightly in any direction

Summary Table: Apparatus Dimensions & Tolerances

flowchart LR
    A[Specimen Drying] -->|Oven at 70 ± 5 ℃ for 48h| B[Cooling in Desiccator (20-30 ℃)]
    B --> C[Mass Measurement]
    C -->|Mass difference ≤ 0.1%| D[Ready for Testing]

    E[Testing Machine] --> F[Steel Bearing Plates ≥10mm thick]
    F --> G[Spherical Seat Plate]
    F --> H[Plain Rigid Plate]
    G & H --> I[Load Application on Specimen]

This ensures accurate, repeatable compressive strength testing per IS 1121 (Part 3): 2012.

IS 1121 Part 3: Test Procedure Key Points

Specimen Preparation (Clause 4.3.2)

• Dry specimens in an oven at 70 ± 5 °C for 48 hours.
• Cool in desiccator to room temp (20–30 °C).
• Achieve constant mass: two consecutive hourly mass readings differ by ≤ 0.1%.

Testing Machine Setup

• Capacity: Sufficient for test load.
• Loading rate: Uniform at 200 N/s until specimen splits.
• Plates:
  • Two steel bearing plates, ≥10 mm thick, hardened faces.
  • One plate with spherical seating (center aligned with plate face center).
  • Other plate: plain rigid bearing block.
  • Bearing face width: > 25 mm.
  • Length: equal to specimen length.
  • Flatness tolerance: deviation ≤ 0.0125 mm.
  • Spherical plate must freely rotate and tilt slightly.

Test Procedure (Clause 6.1)

• Sandwich specimen between two steel plates (25 mm wide, 10 mm thick, length = specimen length).
• Apply load continuously and without shock at 200 N/s.
• Record max load at failure with ±1% accuracy.

Number of Specimens (Clause 4.3)

• Use 5 specimens per condition (dry and other specified conditions).

Reporting (Clause 7)

• Round off results per IS 2:1960 rules.

Summary Table: Test Setup Parameters

flowchart TD
    A[Prepare Specimens] --> B[Dry at 70 ± 5°C for 48h]
    B --> C[Cool in des

IS 1121 (Part 3): Evaluation and Report of Test Results

Key Specifications & Procedures

• Test Setup (Clause 6.1):

  • Specimen sandwiched between steel plates:
    • Width = 25 mm
    • Thickness = 10 mm
    • Length = specimen length
  • Load applied uniformly at 200 N/s until failure.
  • Record maximum load (N) with ±1% accuracy.

• Result Reporting (Clause 7):

  • Round off values per IS 2:1960 rules.
  • Report size & shape of test specimen in mm (Clause 7.6).
  • Use average of 5 tests if individual results vary ≤ ±15% (Clause 7.3). Otherwise, repeat tests.

Tensile Strength Calculation

[ \text{Tensile Strength} = \frac{P_{\max}}{A} ]

• (P_{\max}) = Maximum load at failure (N)
• (A) = Cross-sectional area of specimen (mm²)

Summary Table for Reporting

flowchart TD
    A[Test Specimen] --> B[Sandwiched between steel plates]
    B --> C[Load applied at 200 N/s]
    C --> D[Specimen splits at max load]
    D --> E[Record max load P_max]
    E --> F[Calculate tensile strength = P_max / Area]
    F --> G[Report average of 5 tests if variation ≤ ±15%]
    G --> H[Round off values as per IS 2:1960]

This ensures standardized, accurate evaluation and reporting of tensile strength in building stones.

IS 1121 Part 3: Committee Composition Summary

Committee Composition for Stones Sectional Committee, CED 6 includes representatives from:

• Government & Research Institutes:

  • Central Building Research Institute (CSIR), Roorkee
  • Central Public Works Department, New Delhi
  • Indian Institute of Technology, Chennai
  • Geological Survey of India, Kolkata
  • Indian Bureau of Mines, Nagpur
  • Military Engineer Services, Army Headquarters
  • Public Works Departments (Delhi, Rajasthan, Tamil Nadu)
  • National Council for Cement and Building Materials, Ballabgarh

• Industry & Associations:

  • Associated Stones Industries (Kotah) Ltd.
  • Builders Association of India, Mumbai
  • Gem Granites, Chennai
  • Stone Technology Centre & Foundation, Jaipur
  • Tamilnadu Minerals Limited, Chennai
  • The Indian Institute of Architects, Mumbai

• BIS Officials:

  • Chairperson: Dr. A. K. Dhawan
  • Member Secretaries: Shri Sanjay Pant, Shri S. Arun Kumar

Notes:

• The committee is multidisciplinary, ensuring comprehensive coverage of stone testing and standards.
• No specific formula or table for committee composition exists; it is defined by expert representation from key organizations.
• For test specimen dimensions and evaluation, refer to Clause 7.6 and Fig.1 for tensile strength testing (dimensions in mm).

graph TD
    A[Stones Sectional Committee (CED 6)] --> B[Government & Research Institutes]
    A --> C[Industry & Associations]
    A --> D[BIS Officials]
    B --> E[CSIR, IIT, GSI, PWD, MES]
    C --> F[Stone Industries, Builders Assoc., Architects]
    D --> G[Chairman & Member Secretaries]

For detailed testing procedures and specimen sizes, refer to Clause 7.6 and Fig.1 in IS 1121 (Part 3): 2012.