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IS 1121:1974 Part 1 is the Indian Standard (BIS) for methods of test for determination of strength properties of natural building stones - part 1: compressive strength. This part of IS 1121 prescribes the standard testing method for determining the compressive strength of natural building stones. It guides material engineers on sample preparation, conditioning, and loading to evaluate the load-bearing capacity of stone used in masonry and civil construction.
Prescribes the method for determining the compressive strength of natural building stones.
! Stones are highly anisotropic; ensure you test and report strengths both parallel and perpendicular to the bedding planes or rift.
! The bearing surfaces of the specimens must be strictly flat and parallel to ensure uniform stress distribution; capping with plaster of Paris may be required if perfectly smooth surfaces cannot be achieved.
! Moisture severely affects the strength of natural stone; tests are typically conducted in both completely dry and saturated conditions.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
natural building stonesstonerockmasonry
International Equivalents
Similar International Standards
ASTM C170 / C170M - 17ASTM International, USA
HighCurrent
Standard Test Method for Compressive Strength of Dimension Stone
Both standards specify procedures for determining the uniaxial compressive strength of natural dimension stone.
EN 1926:2006CEN (European Committee for Standardization), Europe
HighCurrent
Natural stone test methods - Determination of uniaxial compressive strength
Both provide methods for determining the compressive strength of cubic or cylindrical natural stone specimens.
ASTM D7012 - 14e1ASTM International, USA
MediumCurrent
Standard Test Method for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens under Varying States of Stress and Temperatures
Overlaps in testing uniaxial compressive strength (Method C), but D7012 is broader and more focused on rock mechanics/geotechnical applications.
Key Differences
≠Specimen Geometry: IS 1121 primarily uses cubes (40, 50, 70mm) or 1:1 aspect ratio cylinders. In contrast, ASTM C170 specifies 2:1 aspect ratio cylinders, which significantly affects the failure mode and resulting strength value.
≠Loading Rate: The rate of loading in IS 1121 is ~13.7 MPa/min, which is substantially slower than ASTM C170 (36 ± 6 MPa/min) and EN 1926 (60 ± 30 MPa/min). Slower rates can result in lower measured strength values.
≠Specimen Conditioning: Drying temperature in IS 1121 is 105°C, while ASTM C170 specifies a lower 60°C and EN 1926 uses 70°C. The higher temperature in the IS code could potentially induce micro-cracking in some stone types before testing.
≠Number of Specimens: IS 1121 requires a minimum of three specimens, whereas ASTM C170 requires five, and EN 1926 requires ten. This difference impacts the statistical confidence of the reported average strength.
Key Similarities
≈Test Objective: The fundamental purpose of all standards is identical: to determine the maximum uniaxial compressive stress a natural stone specimen can withstand before failure.
≈Use of Spherical Seating: All compared standards mandate the use of a spherically seated bearing block on the testing machine to ensure uniform load distribution and to accommodate minor non-parallelism of specimen loading faces.
≈Testing in Wet and Dry Conditions: Both IS 1121 and ASTM C170 explicitly define procedures for testing specimens in both oven-dried and water-saturated (wet) conditions to assess the stone's performance in different moisture states.
≈Calculation of Strength: The method of calculation is consistent across all standards, where compressive strength is determined by dividing the maximum applied load at failure by the specimen's initial cross-sectional area.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Specimen Shape
Cube (e.g., 50x50x50 mm) or Cylinder (H:D = 1:1)
Cylinder (H:D = 2:1) or Cube (50.8 mm)
ASTM C170
Minimum Number of Specimens
3
10
EN 1926
Loading Rate (Stress Rate)
~140 kg/cm²/min (~13.7 MPa/min)
1.0 ± 0.5 MPa/s (60 ± 30 MPa/min)
EN 1926
Dry Conditioning Temperature
105 ± 5 °C
60 ± 2 °C
ASTM C170
Wet Conditioning Immersion Period
72 hours
48 hours
ASTM C170
Parallelism Tolerance of Faces
Not explicitly quantified ('truly parallel')
Within 0.05 mm in 50 mm
ASTM C170
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
specimen dimensions50 mm cubes or cylinders 50 mm diameter x 50 mm height
loading rate14 N/mm² per minute
dry conditioning temp105 ± 5°C
dry conditioning time24 hours
water immersion time72 hours at 20 to 30°C
bearing surface tolerance0.025 mm
Key Formulas
C = W / A — Compressive Strength (where W is crushing load in N, A is area of bearing surface in mm²)