METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 29 
shall be sieved through a No. 16 (1,190-mieron) sieve and all lumps rejected. 
Aggregates shall be in a room-dry condition when used in concrete tests. In 
general, aggregates should be separated on the No. 4 (4,760-micron), %-inch 
and 1 %-inch sieves and recombined to the average original sieve analysis for 
each batch. Fine aggregate should be separated into different sizes also in 
cases where unusual gradings are being studied. 
3. Representative samples of all concrete materials shall be secured for pre- 
liminary tests prior to the proportioning and mixing of the concrete. Cement 
test samples may be made up of a small quantity from each sack used in the 
concrete tests. Test samples of aggregates may be taken from larger lots by 
quartering. 
4. Cement shall be tested in accordance with the methods described in the 
standard specifications and tests for Portland cement (serial designation C !>, 
see p. 3) of the American Society for Testing Materials (4). 
5. Fine aggregates (passing through a No. 4 (4,760-micron) sieve) shall be 
subjected, when required, to the following tests of the American Society for 
Testing Materials: 
(a) Sieve-analysis test made in accordance with the standard method of test 
for sieve analysis of aggregates for concrete < serial designation C 41, see p. 36 
(-'/)). 
(6) Test for organic impurities made in accordance with the standard method 
of test for organic impurities in sands for concrete ( serial designation 
C 40, seep. 28 (//)). 
(c) Test for quantity of silt. clay, and dust made in accordance with the 
tentative method of decantation test for sand and other fine aggregates (serial 
designation D 136-22 T. see p. 21 (j) ). 
(d) Test for unit weight made in accordance with the standard method of 
test for unit weight of aggregate for concrete (serial designation C 29. see p. 27 
(4)). 
(e) Strength test of 1:3 mortar by weight at 7 and 28 days in comparison 
with standard sand mortar in accordance with standard specifications and tests 
for Portland cement (serial designation C 9, see p. 3 (4) )• 
6. Coarse aggregates (retained on a No. 4 (4,760-micron) sieve) shall be 
subjected when required to the following tests: 
(a) Sieve analysis test as specified in section 5 (a). 
(&) Test for quantity of silt, clay, and dust made in accordance with standard 
method of test for quantity of clay and silt in gravel for highway construction 
(serial designation D 72. see p. 21) of the American Society for Testing Mate- 
rials (.{). 
(c) Test for unit weight as specified in section 5 (d). 
7. The unit weight of mixed fine and coarse aggregates as used in concrete 
tests shall be determined in accordance with the method specified in sec- 
tion 5 ((f). 
8. The quantities of each size of aggregate to be used in each batch shall 
be determined on the basis of the sieve analysis and the unit weight of the 
mixed aggregate. The exact quantities of cement and of each size of aggregate 
for each batch shall be determined by weight. The quantity of water for each 
batch shall be accurately measured. The quantities of materials may be ex- 
pressed as (a) 1 volume of cement to volumes of total aggregate mixed 
as used, or (b) 1 volume of cement, volumes of fine aggregate, and 
volumes of coarse aggregate, or (c) 1 part by weight of cement, 
part* by weight of fine aggregate, and parts by weight of coarse 
aggregate. 15 
9. Compression tests of concrete shall be made on cylinders of diameter 
equal to one-half the length. The standard shall be 6 by 12 inch cylinders 
where the coarse aggregate does not exceed 2 inches in size: for aggregates 
larger than 2 inches, 8 by 16 inch cylinders shall be used ; 2 by 4 inch cylinders 
may be used for mixtures without coarse aggregate. 
10. (a) Concrete shall be mixed by hand in batches of such size as to leave 
a small quantity of concrete after molding a single test specimen. The batch 
15 It is impracticable to give a general method for proportioning concrete for experi- 
mental purposes ; the details will necessarily vary widely with the purpose for which 
the tests are made. The following procedure is suggested for specific cases : ( a I 
Vary the cement content by 10 per cent intervals above and below assumed quan- 
tity. (&) Vary the proportions of fine to coarse aggregate, measured separately, at 
intervals of 10 per cent, (e) Vary the quantity of mixing water bv intervals of 10 
per cent. 
