METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 0/ 
Example : 
Weight of sand, 100 pounds per cubic foot. 
Weight of cement. 94 pounds per cubic foot. 
Required, 75 cubic inches of mortar. 
Quantity of sand,^^X100X453.6=l,969 grams. 
Quantity of cement. -=^ X 94X453.6=617 grams. 
36. METHOD OF SAMPLING MINERAL FILLER 
Mineral filler shall be sampled according to the method for sampling Portland 
cement received in carload lots. 
37. METHOD FOR DETERMINATION OF FINENESS OF 
MINERAL FILLER 
1. The fineness test of mineral filler shall be made on a 200-mesh sieve which 
meets the requirements of the 200-mesh sieve specified for Portland cement. 
2. The test shall be made with 50 grams of filler. The sieve shall be thor- 
oughly clean and dry. The filler shall be placed on the No. 200 sieve, with a 
pan and cover attached, if desired, and shall be held in one hand in a slightly 
inclined position 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 ether hand on the upstroke. The sieve shall be turned every 25 
strokes about one-sixth of a revolution in the same direction. The operation 
shall continue until not more than 0.05 gram passes through in one minute of 
continuous 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. 
3. Mechanical sieving devices may be used, but the filler shall not be rejected 
if it meets the fineness requirement when tested by the hand method described 
in section 2. 
38. METHOD OF PROPORTIONING NATURAL SAND AND 
GRAVEL FOR CONCRETE CONSTRUCTION 
For determining the amount of cement t<> make concrete equivalent to any 
base mixture, when the percentage of sand in the total aggregate varies from 
the base mixture. 
Rile. — Decrease or increase the ratio by weight of total aggregate to cement 
by 0.05 times the increase, or decrease in the percentage of sand in the total 
aggregates by weight. This involves the following steps in the process: 
1. If the base mixture is stated as a relation by volume, it w T ill be necessary 
to transfer the proportion to a statement of relation by weight. This requires 
that the weights per unit of loose volume of the various materials be known 
or assumed. 
2. Determine the percentage of fine aggregate in the total aggregate in the 
ba-e mixture and in the new mixture to be used, using the weight proportions. 
3. Multiply the difference between these two percentages by 0.05 and sub- 
tract the result from the sum of the parts of fine and coarse aggregates in 
Die weight proportion for the base mixture if the percentage of fine aggregate 
is greater in the new mixture. If the percentage of fine aggregate is less in 
the new mixture, add instead of subtracting. 
4. If screened materials are to be used, divide the parts of total aggregate 
determined above into fine and coarse aggregate according to the percentage of 
fine aggregate in the new mixture. 
5. Transfer the resulting weight proportion into a statement of relation by 
loose volumes. 
Example : 
Assume — Base mix. 1:2: 3% by volume. 
Unit weights — 
Fine aggregate. 95 pounds per cubic foot, 
Coarse aggregate. 110 pounds per cubic foot, 
Cement. 94 pounds per cubic foot. 
Percentage of fine aggregate in new mixture=60. 
