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IS 9669:1980 is the Indian Standard (BIS) for cbr moulds and their accessories. This standard specifies the material, dimensional, and constructional requirements for the moulds and their accessories used for the determination of the California Bearing Ratio (CBR) of soils. It ensures that the equipment used for this critical geotechnical test is standardized, leading to consistent and repeatable results across different laboratories.
! This standard only covers the specifications for the CBR apparatus. The actual test procedure is detailed in IS 2720 (Part 16).
! Regularly check for any deformation or corrosion on the internal surfaces of the mould as it can significantly affect soil compaction and the final CBR value.
! Verify the mass of the surcharge weights and the dimensions of the plunger periodically to ensure compliance and accuracy.
Standard Test Method for California Bearing Ratio (CBR) of Laboratory-Compacted Soils
Specifies the apparatus for the CBR test, with very similar mould dimensions (diameter and height) to IS 9669.
AASHTO T 193-13 (2021)American Association of State Highway and Transportation Officials, USA
HighCurrent
Standard Method of Test for The California Bearing Ratio
Nearly identical to ASTM D1883, it details apparatus requirements that closely mirror the IS code.
BS 1377-4:1990British Standards Institution, UK
MediumCurrent
Methods of test for soils for civil engineering purposes. Compaction-related tests
Covers the CBR test but specifies a significantly shorter mould (127 mm vs 175 mm in IS code).
BS EN 13286-47:2021European Committee for Standardization (CEN), Europe
MediumCurrent
Unbound and hydraulically bound mixtures. Test methods. California bearing ratio, immediate bearing index and linear swelling
The current European standard for CBR, which also specifies a shorter mould (120 mm) similar to the older BS code.
Key Differences
≠The standard mould height in IS 9669 is 175 mm, which is very close to the ASTM/AASHTO standard of 177.8 mm (7 in). However, BS 1377-4 and BS EN 13286-47 specify much shorter moulds of 127 mm and 120 mm respectively.
≠The spacer disc height in IS 9669 is 47.7 mm to achieve a final specimen height of ~127 mm. In contrast, the ASTM/AASHTO spacer disc is taller at 61.4 mm (2.416 in) to achieve a specimen height of ~116 mm.
≠The mass of the heavy compaction rammer specified in the related Indian standard (IS 2720-8) is 4.89 kg, whereas the ASTM/AASHTO standard (ASTM D1557) specifies a 4.54 kg (10 lbf) rammer, and BS 1377 specifies a 4.5 kg rammer.
≠Individual surcharge weights are specified as 2.5 kg in IS 9669, while they are 2.27 kg (5 lb) in ASTM/AASHTO and 2.0 kg in BS 1377.
Key Similarities
≈All major standards (IS, ASTM, AASHTO, BS, EN) specify a nominal internal mould diameter of 150 mm or its direct imperial equivalent (152.4 mm / 6 in).
≈The penetration piston has a consistent nominal diameter of 50 mm (or its imperial equivalent of 49.63 mm / 1.954 in) across all compared standards, ensuring a uniform area of load application.
≈The basic assembly of the apparatus is the same, comprising a mould body, a detachable collar for compacting taller specimens, and a detachable perforated base plate.
≈All standards specify the use of annular and slotted surcharge weights to simulate the confining pressure of overlying pavement layers during the soaking and penetration phases of the test.
Parameter Comparison
Parameter
IS Value
International
Source
Mould Internal Diameter
150 mm
152.4 ± 0.66 mm
ASTM D1883-21
Mould Internal Height
175 mm
177.8 ± 0.46 mm
ASTM D1883-21
Mould Internal Height
175 mm
127 ± 0.5 mm
BS 1377-4:1990
Spacer Disc Height
47.7 mm
61.4 ± 0.25 mm
ASTM D1883-21
Penetration Piston Diameter
50 mm
49.63 ± 0.13 mm
ASTM D1883-21
Heavy Compaction Rammer Mass
4.89 kg (per IS 2720-8)
4.54 kg (10 lbf)
ASTM D1557 (for D1883)
Standard Surcharge Weight (each)
2.5 kg
2.27 ± 0.04 kg (5 lb)
ASTM D1883-21
Detachable Collar Height
50 mm
50.8 mm (2 in)
ASTM D1883-21
⚠ Verify details from original standards before use
What is the standard internal diameter and height of a CBR mould?+
The internal diameter is 150 mm and the height is 175 mm (Clause 3.1.1).
What is the specified mass for an individual surcharge weight?+
Each surcharge weight, whether annular or slotted, should have a mass of 2.5 kg (Clauses 3.4.1 & 3.5.1).
What is the diameter of the penetration plunger used in the CBR test?+
The plunger should have a diameter of 50 mm (Clause 3.6.1).
What is the purpose of the spacer disc?+
The spacer disc is placed inside the mould during compaction of soaked specimens. It is removed before the soaking and penetration test to allow for swelling and measurement.