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IS 9745:1981 is the Indian Standard (BIS) for method for determining strength-giving properties of asbestos fibre. This standard specifies the method for determining the strength-giving properties of asbestos fibres for use in asbestos-cement products. It details the procedure for preparing standard test specimens of asbestos-cement and determining their modulus of rupture through a flexural strength test.
Method for determining strength-giving properties of asbestos fibre
! This standard is effectively obsolete for new construction due to the widespread ban and severe health hazards (carcinogenic properties) associated with asbestos. Its modern application is primarily in forensic engineering or historical material analysis.
! Handling of asbestos fibres requires extreme caution, specialized containment facilities, and appropriate personal protective equipment (PPE) to prevent inhalation of fibres.
! The 'strength-giving property' is quantified as the Modulus of Rupture (flexural strength) of a standard specimen made with the fibre.
ASTM D3880-90 (1999)ASTM International (American Society for Testing and Materials), USA
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Standard Test Method for Asbestos Strength Units
Defines the referee method for determining strength units of asbestos, identical in principle and practice.
QAMA Method for Determination of Strength UnitsQuebec Asbestos Mining Association (QAMA), Canada
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Standard Method for the Determination of Strength Units of Asbestos Fibre
The original industry method from which both IS 9745 and ASTM D3880 are derived.
ISO 7506:1984ISO (International Organization for Standardization)
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Method for determination of asbestos fibre strength by the mR/D test
Specifies a different method (mR/D test) for determining fibre strength, not directly comparable to the Strength Unit method.
Key Differences
≠IS 9745 references Indian standards for materials, such as IS 269 for Portland cement, whereas international equivalents reference their respective national standards (e.g., ASTM C150 for cement in ASTM D3880).
≠IS 9745 provides both a 'Referee Method' (Appendix A) and a 'Routine Method' (Appendix B), which is a simplified procedure. ASTM D3880 primarily focuses on the single, more rigorous referee method.
≠While the IS and ASTM methods are nearly identical, other international methods like the former ISO 7506 used a completely different principle (mR/D test), which involves different specimen preparation, testing, and calculation, yielding non-correlatable results.
Key Similarities
≈The 'Referee Method' in IS 9745 is a direct adoption of the QAMA/ASTM method, using a slurry of asbestos fibre, Portland cement, and silica to form test specimens.
≈The procedure for forming test specimens is identical, involving the creation of circular pats of 101.6 mm (4 inches) diameter from the slurry using a vacuum filtration apparatus.
≈The curing protocol for test specimens is the same, specifying immersion in a water bath at 20 ± 1°C for 28 days before testing.
≈The final calculation of 'Strength Units' (SU) is derived from the Modulus of Rupture (flexural strength) and bulk density of the test pats using a virtually identical formula.
Parameter Comparison
Parameter
IS Value
International
Source
Final Strength Metric
Strength Units (SU)
Strength Units (SU)
ASTM D3880-90
Referee Test - Asbestos Fibre Mass
3.00 g
3.00 g
ASTM D3880-90
Referee Test - Portland Cement Mass
90.0 g
90.0 g
ASTM D3880-90
Referee Test - Silica Mass
60.0 g
60.0 g
ASTM D3880-90
Test Specimen Diameter
101.6 mm
101.6 mm (4.0 in)
ASTM D3880-90
Curing Duration
28 days
28 days
ASTM D3880-90
Curing Water Temperature
20 ± 1°C
20 ± 1°C
ASTM D3880-90
Strength Unit Formula Constant
10.84 x 10^3
10 840
ASTM D3880-90
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Standard specimen dimensions160 mm x 40 mm x 6 mm
Curing period for specimens28 days in water
Number of test specimens6
Moulding pressure for specimen31.4 MPa
Span for flexural strength test140 mm
Key Formulas
Modulus of Rupture (R) = (3 * P * l) / (2 * b * d^2) — Where P is breaking load, l is span, b is width, and d is thickness.
To evaluate and compare the reinforcing capability of different types of asbestos fibres when mixed with cement.
Why is this code rarely used today?+
Because asbestos is a known carcinogen and its use in building materials is banned or heavily restricted in India and globally, making this test irrelevant for modern materials.
What is the final result obtained from this test?+
The Modulus of Rupture (R), expressed in MPa, which indicates the flexural strength of the standardized asbestos-cement specimen.
What are the main components of the test specimen?+
The test specimen is made from a mix of asbestos fibre, ordinary Portland cement, and ground silica, mixed with water (Clause 4).