32 
BULLETIN 1216, Q. S. DEPARTMENT OF AGRICULTURE. 
The No. 200 sieve should have 200 wires per inch, and the num- 
ber of wires in any whole inch shall not be outside the limits of 
182 to 208. No opening between adjacent parallel wires shall 
be more than 0.0050 inch in width. The diameter of the wire 
should be 0.0021 inch and the average diameter shall not he out- 
side the Limits 0.0019 to 0.0023 Inch. The ralue of the sieve as 
determined by sieving tests made in conformity with the stand- 
ard specification for these tests on a standardized cement which 
gives a residue of -•") to 20 per cent on the No. 200 sieve, or on 
other similarly graded material, shall not show a variation of 
more than 1.5 per cent above or below the standards maintained 
at the Bureau of Standards. 
34. The test shall be made with r><> grams of cement The 
sieve shall be thoroughly clean and dry. The cement shall be 
placed on the No. 200 sieve, with pan and cover attached, if de- 
sired, and shall be held in one hand in a slightly inclined posi- 
tion so that the sample will be well distributed over the sieve. 
at the same time gently Striking the side about 150 times per 
minute against the palm of the other hand on the upstroke. The 
sieve shall be turned every 25 strokes about one-sixth of a revolu- 
tion in the same direction. The operation shall continue until 
not more than 0.05 gram passes through in one minute of continu- 
ous Sieving. The fineness shall be determined from the weight 
of the residue on the sieve expressed as a percentage of the 
weight of the original sample. 
35. Mechanical sieving devices may be used, but the cement 
shall not be rejected if it meets the fineness requirement when 
tested by the hand method described in section 34. 
X. MIXING CEMENT PASTES AND MORTARS. 
Pastes and 36. The quantity of dry material to be mixed at one time shall 
mortars. not exceed l.(KK) grams nor be less than 500 grams. The propor- 
tions of cement or cement and sand shall be stated by weight 
in grams of the dry materials; the quantity of water shall be 
expressed in cubic centimeters (1 cubic centimeter of water=l 
gram). The dry materials shall be weighed, placed upon a non- 
absorbent surface, thoroughly mixed dry if sand is used, and a 
crater formed in the center, into which the proper percentage or 
clean water shall be poured; the material on the outer edge shall 
be turned into the crater by the aid of a trowel. After an inter- 
val of one-half minute for the absorption of water the operation 
shall be completed by continuous, vigorous mixing, squeezing 
and kneading with the hands for at least one minute. 10 During 
the operation of mixing, the hands should be protected by rubber 
gloves. 
37. The temperature of the room and the mixing water shall be 
maintained as nearly as practicable at 21° C. (70° F.). 
Normal 
consistency. 
XI. NORMAL CONSISTENCY. 
'AS. The Vicat apparatus consists of a frame bearing a movable 
rod. weighing 300 grams, one end being 1 centimeter in diameter 
for a distance of <» centimeters, the other having a removable 
needle 1 millimeter in diameter, <"> centimeters long. The rod is 
reversible, and can be held in any desired position by :i screw, and 
has midway between the ends a mark which moves under a scale 
(graduated to millimeters) attached to the frame. The paste is 
field in a conical, hard-rubber ring 7 centimeters in diameter at 
, " In order to secure uniformity in the results of tests for the time 
of Betting and tensile strength the manner of mixing above described 
should lie carefully followed. At least one minute is accessary to ob- 
tain Hie desired plasticity which is not appreciably affected by continu- 
ing the mixing for several minutes. The ezad time necessary is de- 
pendenl upon the personal equation (it the operator. The error in 
mixing should 1)" on the side of overmixing. 
