IS 2720 (PART V), BS 1377-2 , ASTM D 4318
Casagrande method in mechanical form is known as liquid limit
method and has been in use for soil mechanics for a number of
decades. The liquid limit data of soils is useful to correlate
mechanical properties of soil, such as compressibility and lower
shear strength. Liquid limit is the water content at which soil passes
from zero strength to an infinite strength, hence the true value of
liquid limit cannot be determined. For determination purpose liquid
limit is that water content at which a part of soil, cut by a groove of
standard dimensions, will flow together for a distance of 1.25cm
under an impact of 25 blows in a standard liquid limit apparatus. The
soil at the water content has some strength which is about
0.17N/cm. sq. (17gms/sq.cm.) . At this water content soil just passes
from liquid state to plastic state. It consists on a brass cup held on an
adjustable bracket. The cup can be adjusted for a fall of 1 cm and can
be raised an dropped on a rubber base of standard hardness by cam
action. Complete with one Casagrande grooving tool, one ASTM
grooving tool and a height gauge block.
Same as above but fitted with a counter to register the number of
blows.