Quality Assurance Handbook for Rural Roads Volume-I - pmgsy

Appendix-1
(ii) Make two identical pats of 75 mm dia and 12 mm thick of neat cement paste, one with water
under test and the other with water of known suitability. Place the pats on a clean nonabsorbent
surface and leave for 48 hours, and setting and hardening time observed for both
the pats. If the quality of water under test is not upto mark, both setting and hardening time
of the pat would be different from the one of known quality.
4.2 Cement
Cement more than three (3) months old shall be got tested to ascertain its quality and satisfy the
acceptability requirements as per Table 800.11. The quality of cement can be roughly judged by
the following:
(i) Thrust a hand into a cement bag. It must give cool feeling. There should be no lump inside.
(ii) Take a pinch of cement and feel between the fingers. It should give a smooth and not a
gritty feeling.
(iii) Take a handful of cement and throw it in a bucket full of water. The particles should float
for sometime before they sink.
(iv) Take about 100 gm of cement and mix it with water to make a stiff paste. Make a cake with
sharp edges. Put it on a glass plate and slowly take it under water in a bucket, without
disturbing the shape of cake. After 24 hours, the cake should retain its original shape and
gain some strength.
(v) Setting time: Make a stiff paste of neat cement and water, and form it into a pat of about 75
mm dia and 12 to 25 mm thick. The pat should commence to set in 30 to 60 minutes. The
commencement of setting can be roughly estimated by pressing the uncut end of a lead
pencil into mass. The resistance to piercing increases suddenly when setting commences.
In 18 to 24 hours, the pat should have hardened sufficiently so that a scratch can be made
with a thumb nail.
(vi) Soundness: Boil the set pat (as above) in water for about 5 hours. The pat should remain
sound and hard and should not swell, crack or disintegrate, but may show only hair cracks.
Reject cement if pat shows radial cracks or curl or crumble.
(vii) Fineness: In the sieve test, 100 gm cement is correctly weighed and placed on 90 micron
sieve. Air set lumps, if any, are broken down with fingers. The sample is sieved for 15
minutes and the residue left on the sieve is weighed. The amount of residue should not
exceed 10% for OPC.
4.3 Sand or Fine Aggregate
The sand should be sharp, clean, chemically inert, coarse and gritty to the touch and free from
silt/clay and organic impurities. The general quality of sand can be assessed as below:
(i) Presence of Silt or Clay: Rub a sample of sand between damp hands and note the
discolouration caused on the palm. If the sand is clear, the palm would be stained slightly.
If the hands stay dirty after sand has been thrown away, it indicates too much of silt or clay.
(ii) Sedimentation: Place, without drying, a sample of sand in a 200 ml measuring cylinder
upto 100 ml mark. Add clean water upto 150 ml mark. Shake the contents vigorously and
allow it to settle for 3 hours. The height of the silt visible as a layer above the sand is expressed
as a percentage of the sand below.
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