7 
“EXAMINATION: OF BITUMINOUS ROAD MATERIALS. 39 
top sieve, after which the cover is put on and the stack agitated for 
about five minutes with both rocking and circular shaking. Each sieve 
is removed in order, and shaken and tapped on a clean piece of paper 
until no appreciable amount of material comes through. Al! lumps 
_are broken up by crushing them against the side of the sieve with the 
finger or a smail spatula. The contents of the sieve are emptied into 
the pan of the balance. All particles caught in the mesh are removed 
by brushing across the underside of the sieve and are added to the 
contents of the pan. As great opportunity exists for wide variations 
in the results of sand gradings made by different persons, owing to 
the possibility of always getting a little more material to pass by 
continued shaking, it is well for the novice to repeat his sifting on 
any given mesh, after having weighed it, in order to see what fur- 
ther loss he can produce. If his judgment has not erred, several 
minutes’ further sifting should not produce a loss of over 0.5 gram. 
Where coarse aggregates have considerable material passing a 10- 
mesh sieve and it is desired to grade this material further, it should 
be weighed and well mixed, quartered, if necessary, and a 100-gram 
sample should be passed through the sand sieves. From the per- 
centages so obtained and the weight of material passing the 10-mesh 
sieve, the percentages of the total aggregate which these finer mate- 
rials represent may be calculated. 
The Office of Public Roads and Rurai Engineering has adopted the 
following recommendations of the Committee on Standard Tests for 
Road Materials of the American Society for Testing Materials as to 
the size of wire for standard sand sieves: 
Diameter | Diameter 
Meshes per linear inch: | Coa Meshes per linear inch: a 
ei Zils SS ee ee Seen 0. 027 DORE ve ce A OOO 
LO ok ge oak eae eee . 0165 80. - . 00575 
Dees ser ckirs ee RS . 91375 | OO ca eae EPs Gnas ee tiie! . 0045 
40 . 01025 | ON Boe ake ee . 00235 
DETERMINATION OF VOIDS IN THE MINERAL AGGREGATE. 
EQUIPMENT. 
1 1,000-cubic-centimeter graduated glass cylinder. 
1 500-cubic-centimeter graduated glass cylinder. 
2 pieces brass tubing (4-inch bore and 2 inches long). 
1 wooden block mounted with soft rubber pad. 
1 iron support with condenser clamp. 
3 feet rubber tubing. 
1 pinchcock. 
1 14-inch stiff flat brush. 
1 small tin scoop. 
2 sheets of manila paper. 
