METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 27 
19. METHOD OF TEST FOR UNIT WEIGHT OF AGGREGATE 
FOR CONCRETE 
(A. S. T. M. method U), serial designation C 29-27) 
1. This method is intended to cover the determination of unit weight of fine, 
coarse, or mixed aggregate for concrete. 
2. {a) The apparatus required consists of a cylindrical metal measure, a 
tamping rod, and a scale or balance, sensitive to 0.5 per cent of the weight of 
the sample to be weighed. 
(&) Measures. — The measure shall be of metal, preferably machined to accu- 
rate dimensions on the inside, cylindrical in form, water-tight, and of sufficient 
rigidity to retain its form under rough usage, with top and bottom true and 
even, and preferably provided with handles. 
The measure shall be of 0.1, 0.5, or 1 cubic foot capacity, depending on the 
maximum diameter of the coarsest particles in the aggregate, and shall be of 
the following dimensions: 
Capacity (cubic foot) 
Inside 
diameter 
Inside 
height 
Minimum 
thickness 
of metal, 
U. S. gauge 
Diameter 
of largest 
particles of 
aggregate 
0. 1 
Inches 
6.00 
Inches 
6.10 
No. 
11 
8 
5 
Inch's 
Under Yi. 
0.5 
10.00 11.00 
14.00 
Under \y 2 . 
1. 
Over \Yi. 
(c) Tamping rod. — The tamping rod shall be a straight metal rod % inch 
in diameter and 24 inches in length, with one end tapered for a distance of 1 
inch to a blunt bullet-shaped point. 
3; The measure shall be calibrated by accurately determining the weight of 
water at 16.7° C. (62° F.) required to fill it. The factor for any unit shall be 
obtained by dividing the unit weight of water at 16.7° O. (62° F.) (62.355 
pounds per cubic foot) by the weight of water at 16.7° C. (62° F.) required 
to fill the measure. 
4. The sample of aggregate shall be room dry and thoroughly mixed. 
5. (a) The measure shall be filled one-third full and the top leveled off with 
the fingers. The mass shall be puddled with the tamping rod with 25 strokes, 
evenly distributed over the surface. The measure shall be filled two-thirds full 
and again puddled with 25 strokes as before. The measure shall then be filled 
to overflowing, puddled 25 times, and the surplus aggregate struck off, using 
the tamping rod as a straightedge. 
In puddling the first layer the rod should not be permitted to forcibly strike 
the bottom of the measure. In puddling the second and final layers only 
enough force to cause the tamping rod to penetrate the last layer of aggregate 
placed in the measure should be used. 
(&) The net weight of the aggregate in the measure shall be determined. The 
unit weight of the aggregate shall then be obtained by multiplying the net 
weight of the aggregate by the factor found as described in section 3. 
6. Results with the same sample should check within 1 per cent. 
20. METHOD OF TEST FOR DETERMINATION OF VOIDS IN 
FINE AGGREGATE FOR CONCRETE 
(A. S. T. M. standard method (J,), serial designation C 30-22) 
1. The voids in fine aggregate for cement concrete shall be determined by the 
formula : 
Percentage of voids=- ( ^ ^ * 62.355 ) -wt. 
X100 
Sp.gr. X 62.355 
2. The symbol " sp. gr." represents the apparent specific gravity of the fine 
aggregate as determined by the standard method of test for apparent, specific 
gravity of sand, stone, and slag screenings, and other fine nonbituminous high- 
