Building Materials, Third Edition

w——2

2w—

2g

™Es†2v 229

mortar under test. The moulds are then covered with non-porous plates and small weights are
placed over them. All the three moulds are left undisturbed for one hour. The distance between
the indicator pointers is measured. “The apparatus is then kept in damp air for 48 hours and
is thereafter subjected to steam at atmospheric pressure for 3 hours. The sample is cooled to
room temperature and the distance between the pointers is measured again. The difference in
the two measurements should not be more than 10 mm after deduction of 1mm, to allow for
expansion of added cement, from the measured expansion. The figure so obtained is recorded
as the net expansion due to lime.

€ 

2—
2€
2„2‘sƒX2TWQP2@€—2ˆA“

Seventy gram of hydrated lime is mixed with 70 ml of clean water at a temperature of 27 ± 3°C
and kept for 2 hours. The lime putty so obtained is thoroughly mixed and knocked up with a
trowel. The putty is then spread over a non-porous surface and 10 g of Plaster of Paris is spread
evenly over it and the whole mass mixed rapidly and thoroughly for two minutes. The gauged
material is then pressed in small quantities with the aid of a broad palette knife or spatula into
a ring mould 100 mm in diameter and 5 mm deep. A flat pat of putty is formed by smoothening
off the top surface with not more than 12 strokes of knife. This entire process should be
completed within 5 minutes from the time of adding Plaster of Paris.
Four such pats are formed and left for 30 minutes. There are then transferred to a drying
oven maintained at a temperature between 35-45°C and are kept for 16 hours. If any test pat
shows cracks is rejected. The test pats are then placed horizontally in a steam boiler and
subjected to the action of saturated steam for 3 hours. The pats are then examined for
disintegration popping or pitting
To determine the soundness of fat lime, pat rare prepared by mixing 70 g of hydrated lime,
10 g of Plaster of Paris and 70 ml of water. The pats are subjected to steam and then tested for
disintegration, popping and pipping. If any of these occurs the lime is considered to be
unsound.

† 2‰2 2™&2‘sƒX2TWQP2@€—2†sA“

The Southard Viscometer is used for adjusting the consistency of the putty. Sufficient putty is
put in the filter cloth, which is folded in the form of bag. It is then suspended by cord above the
vessel to allow the putty to drain. The process can be accelerated by applying moderate
pressure by hand on the bag. The consistency of the putty is adjusted to give a slump of 13 mm.
The density of putty is determined by weighing a known volume of this putty, using the
density vessel.

Volume in ml/g of quicklime =


0.70
d1
where d is the density of lime putty.

„—

/2ƒ
#2„2‘sƒX2TWQP2@€—2†ssA“

Six test specimens of size 25 × 25 × 100 mm are prepared from standard lime-sand mortar*
(1 : 3). The filled mould together with its base plate are covered on to with a similar plate should

*the standard lime-sand mortar is prepared using standard sand and either hydrated lime or quick line.