The condition of a soil can be altered by changing the moisture content. The liquid limit is the empirically established moisture content at which a soil passes from the plastic to the liquid state. A knowledge of the liquid limit allows the engineer to correlate several engineering properties with the soil. Two main types of test are used; the Casagrande type (Cup), which has been used for many years, and the cone penetrometer method, which is now the definitive method specified in BS 1377.

Casagrande Method

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Particular design features of the instrument include a positive action horizontal lead screw, which is rapidly adjustable and rigidly fixes the height of cup in relation to the base during the test procedure. The cam mechanism and cup suspension assembly have been designed to withstand constant use with minimum readjustment

Model No. Desc BS/EN ASTM AASHTO
24-0425 Grooving tool Yes - -
24-0434 Liquid limit device - Yes Yes
24-0410 Liquid limit device Yes - -
24-0453 Grooving tool - Yes -
24-0461 Grooving tool - - Yes
24-0417/01 Liquid limit device - motorised Yes - -
24-0430 Glass plate Yes - -

Cone Penetrometer Method

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•Reduces operator error
•Applicable to a wide range of soils
•Gives reproducible test results
•Provides direct measurement of penetration

The method is fundamentally more satisfactory than the Casagrande method as it is essentially a static test depending on the soil shear strength. The test is based on the relationship between moisture content and the penetration of a cone into the soil sample under controlled conditions.

Determines the moisture content at which clay soils pass from a plastic to a liquid state.

Model No. Desc
24-0540 Cone Penetrometer
24-0548 Penetration test cup
24-0544 Test cone
24-0546 Test gauge

Semi-Automatic Cone Penetrometer

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Model No. BS 1377 BS 1924-2 Voltage Weight, kg
24-0545/01 Yes Yes 220-240 V 50/60 Hz 8.6