Friday, December 21, 2012
Sunday, November 25, 2012
CEMENT : FINENESS BY DRY SIEVING REFERENCE : IS 4031 – (PART – 1) 1996
OBJECT TO CHECK PROPER GRINDING OF CEMENT BY MEASURING FINENESS BY
DRY SIEVING
IMPORTANCE During manufacturing,
cement
must
be ground to be uniformly fine
OF TEST otherwise concrete needs large amount of water for mixing which results in bleeding as well
as poor workmanship.
APPARATUS • Test sieve of non-corrodible metal having 150 mm to 200 mm
diam, and 40 mm to 100 mm depth fitted
with 90
µm mesh sieve
cloth of
woven stainless steel or other abrasion resistant non-
corrodible wires.
• Suitable tray with lid to fit sieve size.
• Stoppered jar with blunt ended stirrer rod
• Weighing balance to weigh upto 10 gms to nearest 10 mg.
• Nylon or pure bristle brush (25 mm / 40 mm bristles) for cleaning
sieves.
PROCEDURE Determination of cement
residue :
• Agitate the cement sample
by
shaking
for
2
minutes in
a
stoppered jar
to
disperse the agglomerates. Wait for few minutes.
• Stir the resulting powder gently with dry rod to distribute the fines throughout
the
sample.
• Weigh approx.
10
gm of
cement
and
put
in sieve fitted
with bottom tray and top lid.
• Agitate and shake the sieve thoroughly
• Weigh the residue – retained on sieve.
• Clean
base of sieve gently by brush to remove fine material.
• Find out % (R1) of residue in comparison with total weight of sample.
• Repeat the procedure at least twice till results do not differ by more than 1%.
CEMENT : DETERMINATION OF SETTING TIME REFERENCE : IS 4031 – (PART – 5) 1996
OBJECT TO DETERMINE INITIAL AND
FINAL SETTING TIME
OF
CEMENT
IMPORTANCE The object is to distinguish between,quick setting and normal setting
OF TEST time and to detect the deterioration due to storage.
APPARATUS • Vicat Apparatus
• Balance (capacity 1000 gms,
accuracy 0.1 gm)
• Annular attachment of Vicat Apparatus
& HUMIDITY • Relative Humidity in Laboratory :
65 + 5 %
PROCEDURE On a non-porous platform
• Mix neat cement with
enough water
to give a paste of Standard
Consistency.
• Start stop watch immediately on adding water to cement. Note
Stop watch reading (To)
• Rest
Vicat mould on non-porous plate and fill it completely with
cement paste. Level of top surface and expel air
by shaking.
• Place test block with mould under the rod bearing needle of Vicat
apparatus and bring rod
level with
top of
test specimen.
Release needle slowly and let it
penetrate in the test block.
• Repeat
the procedure until needle stops of distance
of (5 +
0.5) mm from base of test block. Read the stop watch and note the time (T1).
• Replace needle
by
annular
attachment. Repeat
procedure of
releasing the needle till needle makes an impression on top of
test
block while attachment fails to do so.
Read the stop watch
and note time (T2).
CALCULATION Initial
Setting Time (IST) = (T1 – T0)
Final Setting Time (FST) = (T2 – T 0)
REPORTING Report IST & FST to nearest 5 minutes
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