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.

IS 9669

: 1980

CBR moulds and their accessories

CurrentSpecializedSpecificationGeotechnical · Soil and Foundation Engineering

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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.

CBR moulds and their accessories

Quick Reference Values

Mould internal diameter150 mm

Mould height175 mm

Collar effective height50 mm

Base plate thicknessnot less than 10 mm

Surcharge weight (annular or slotted) mass2.5 kg

Penetration plunger diameter50 mm

Spacer disc diameter148 mm

Spacer disc height47.7 mm

Practical Notes

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.