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IS 11275:1985 is the Indian Standard (BIS) for method of test for determination of crudeness and grit content of asbestos fibre. This standard specifies the method for determining the content of crudeness and grit in asbestos fibre. The procedure involves sieving a dried, weighed sample of the fibre on a specified sieve using a mechanical shaker and calculating the percentage of material retained.
Method of test for determination of crudeness and grit content of asbestos fibre
! WARNING: Asbestos is a hazardous material. All handling and testing must be performed with extreme caution, using appropriate personal protective equipment (PPE) and in a well-ventilated area or fume hood to prevent inhalation of fibres.
! Ensuring the sample is dried to a constant mass is critical for accurate results, as moisture content will affect the final weight.
! The test quantifies non-fibrous impurities which can negatively impact the properties of the final asbestos-cement product.
ASTM D2589-88 (Reapproved 1999)ASTM International, USA
HighWithdrawn
Standard Test Method for McNett Wet Classification of Asbestos Fiber
Defines a wet screening method where the coarsest fraction (+14 mesh) is analogous to the 'crudeness' measured in the IS code.
GOST 12871-93Euro-Asian Council for Standardization, Metrology and Certification (EASC)
HighCurrent
Chrysotile asbestos. Test methods.
Includes a test method for determining the mass fraction of admixtures using a wet sieving process, similar to the IS crudeness test.
ISO 7337:2004International Organization for Standardization (ISO), International
MediumCurrent
Asbestos — Determination of chrysotile asbestos fibre content in crysotile asbestos — Gravimetric method
Describes an acid dissolution method to determine fibre purity, which is chemically related to the 'grit' determination step of the IS code.
Key Differences
≠IS 11275 defines a two-step process, first physically separating 'crudeness' by sieving, then chemically determining 'grit' by acid digestion of the crude fraction. Most international standards perform only one of these operations (e.g., physical separation in ASTM D2589, or chemical digestion of the entire sample in ISO 7337).
≠The specified apparatus differs significantly. IS 11275 uses a custom single-sieve apparatus with a stirrer, whereas ASTM D2589 mandates the use of a standardized, multi-tank 'Bauer-McNett Classifier'.
≠The primary sieve size for crudeness/impurity separation varies: IS 11275 uses a 1.70 mm sieve, ASTM D2589 commonly uses a 1.40 mm (14 mesh) sieve as the second-coarsest screen, and GOST 12871 specifies a much finer 0.25 mm sieve for its 'admixture' test.
≠The test endpoint is defined differently. IS 11275 continues the washing process until the effluent is clear, which is a qualitative endpoint. ASTM D2589 specifies a fixed test duration of 20 minutes.
Key Similarities
≈The fundamental principle of all comparable standards (IS 11275, ASTM D2589, GOST 12871) is based on wet screening, where a fibre sample is dispersed in water and washed through a sieve to separate coarse, non-fibrous material.
≈All methods require the initial preparation of a representative sample of a specified mass (e.g., 10g or 20g) to ensure test consistency.
≈The final measurement for the physically separated fraction involves drying the retained material in an oven at a similar temperature (approx. 105-110 °C) to a constant weight and expressing it as a percentage of the initial sample mass.
≈The IS method for grit determination and the ISO 7337 method for purity both utilize hydrochloric acid digestion to separate the acid-soluble asbestos fibre and carbonates from insoluble mineral matter (grit).
Parameter Comparison
Parameter
IS Value
International
Source
Test Sample Mass
20 ± 0.1 g
10 ± 0.05 g
ASTM D2589-88
Crudeness/Impurity Sieve Size
1.70 mm (IS Sieve 170)
1.40 mm (14 mesh screen)
ASTM D2589-88
Drying Oven Temperature
105 ± 5 °C
105 to 110 °C
ASTM D2589-88
Water Flow Rate
Not specified; regulated to wash fibre but not grit through
11 ± 0.4 L/min per tank
ASTM D2589-88
Test Duration (Sieving)
Until clear water passes through
20 minutes
ASTM D2589-88
Acid for Digestion (Grit/Purity)
Hydrochloric acid (1:1 aqueous solution)
Hydrochloric acid (1:1 aqueous solution)
ISO 7337:2004
Crudeness/Impurity Sieve Size
1.70 mm
0.25 mm
GOST 12871-93
⚠ Verify details from original standards before use
Key Values4
Quick Reference Values
Test Sieve Size150-micron IS Sieve (Clause 4.1.1)
Mass of test specimen50 ± 0.1 g (Clause 6.1)
Drying temperature105 to 110 °C (Clause 6.1)
Sieving time10 min (Clause 6.2)
Key Formulas
Crudeness and Grit Content, % by mass = (m1 / m) * 100, where m1 is mass of residue and m is mass of test specimen
To provide a standardized laboratory method to measure the percentage of coarse impurities (crudeness and grit) in a sample of asbestos fibre.
What size sieve is used in this test?+
A 150-micron IS Sieve is specified according to Clause 4.1.1.
Why is it important to measure grit content in asbestos?+
High grit content is undesirable as it can be abrasive to manufacturing machinery and can create weak points in the final product, reducing its strength and durability.
Is this test still relevant?+
Due to the widespread ban on asbestos, its use is very limited. It may be used for quality control in niche permitted applications or for the analysis of existing, older asbestos-containing materials.