Building Materials, Third Edition

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The sieves are arranged one above the other with the coarser sieves at the top and the finer
sieves at the bottom. Sieving is done with a gentle wrist motion. 100 g of the hydrated lime is
placed on the top sieve and is washed through the sieves with a moderate jet of water for not
more than 30 minutes. The residue on each sieve is dried at 100 ± 10°C to constant mass and
weighed. The result is expressed as a percentage of mass of hydrated lime takes.

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Sample of quick lime is sieved through 2.36 mm IS sieve and the residue, if any, is broken and
sieved again until the whole quantity passes through the sieve. The quantity of water required
for slaking is usually 4 times the mass of quick lime, however, it may be as high as 8 times for
certain high calcium limes.
When slaking temperature is specified by the vendor, the temperature of water is adjusted
to ± 2°C and 5 kg of quicklime sample is added in small quantities within 5 minutes. During
this operation, the mix should be stirred continuously. This temperature is maintained for one
hour. The product is allowed to stand for 24 hours from the time the quicklime was added to
water and is allowed to cool gradually to room temperature during this period. The product is
stirred atleast twice during this period; the last stirring is done within one hour before the
expiration of 24 hours. Now sieve first the supernatant liquid and then the remainder after
stirring thoroughly the product through 850-micron IS sieve and subsequently through 300-
micron IS sieve. A temporary filter cloth is fitted to the vessel. The contents of the slaking
vessels are transferred on to the sieves by washing the vessel with a jet of water. The residues
are washed with a jet of water and then dried at 100 ± 10°C to constant mass. The residues on
the two sieves are weighed separately and are reported as percentage of quicklime taken for
the test.

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The test is conducted on a standard flow table and a truncated conical mould (Fig. 8.5).
For testing hydrated lime, the lime putty is prepared by thoroughly mixing 500 g of hydrated
lime with an equal mass of water at a temperature of 27 ± 2°C and kept for 24 hours. The soaked
material is then thoroughly mixed and knocked up to produce a plastic putty, by passing the
material twice through the mixer.
The lime putty is adjusted to standard plastering consistency, which is indicated by an
average spread of the lower part of lime putty to 110 mm with a permissible deviation of not
more than 1 mm, when subjected to one pump on the standard flow table. If consistency is too
stiff, more water is added, and if too wet, a small portion of water is with drawn by placing the
material for a short period on a clean absorbent surface.
The putty is filled in moulds in such a way that no air bubbles or voids are trapped inside.
The temperature during the test is maintained at 27 ± 2°C. The top of the table is cleaned and
dried. The cone of material is applied to the center of the table and the mould withdrawn. The
handle of the flow table is turned steadily and evenly at the rate of one turn per second. The