FORMS FOR SPECIFICATIONS, ETC., FOR ROAD MATERIALS. 51 
be followed, using composite samples. Samples at the mill shall be taken by 
any of the methods of section 18, A. S. T. M. specifications, as may be most 
practicable. 
Field Samples of Concrete. 
(1) When taken. — Samples shall be taken regularly for the general control 
of strength and uniformity on one day of each week of work ; and at irregular 
intervals, whenever a complete change is noted in the character or grading of 
one or more materials or in any element affecting the entire mix. 
(2) Number of samples. — 
(a) In taking regular samples three specimens should be molded to be 
broken one at each of the periods, 14 days, 28 days, and 
(6) In taking irregular samples, nine specimens should be molded, three to 
be broken at each of the periods, 14 days, 28 days, and 
How taken. — The batch sampled for general purpose should be similar in 
consistency and general grading of the aggregate to the regular run of batches 
being turned out. The sample from which specimens are molded should be 
composed of several portions taken during the discharge of one batch in order 
to represent an average of the batch ; or the batch may be dropped upon the sub- 
grade and concrete from several points (taking care to exclude dirt), placed in 
a clean wheelbarrow or other container, avoiding additional mixing. 
Sampling Viteified Paving Brick:. 
Inspection. — Vitrified brick may be inspected and tested at the point of 
manufacture, or they may be sampled at the point of delivery, and representa- 
tive samples submitted to the laboratory for testing prior to acceptance of the 
shipment. 
Plant inspection. — Whenever practicable the inspection and testing of vitri- 
fied brick shall be carried on at the manufacturer's plant. The choice between 
plant inspection and sampling at point of use should be based on the average 
number of brick to be shipped from the plant per day, and the total number 
required for the particular piece of work. 
Whenever conditions permit, samples should be taken directly from the kiln 
during the process of emptying. One or more sets of tests, depending upon the 
size of the kiln, each set consisting of three separate tests, should be made 
on each kiln. Each test in a set of three should represent approximately a 
single degree of burning (based on the position of the bricks in the kiln), and 
all ten of the bricks in a single test should be of the same approximate degree 
of burning. 
The average abrasion loss in three such tests will determine whether the 
contents of a kiln or part of a kiln meet the average maximum abrasion loss 
specified ; and the maximum variation between the per cent abrasion losses of 
the three sets will be used to determine what portion of the bricks represented 
will be culled or rejected. 
Sampling from piles at the plant. — In general, samples selected from piles at 
the plant shall be as nearly as possible representative of the entire run of the 
brick. Samples from piles shall be taken from as many different points corre- 
sponding to the length, breadth, and depth of the pile as possible. In no case 
shall they be confined to the upper or outer few layers. Where controversy 
arises regarding the admissibility of certain types or portions of the lot, entire 
test samples may be selected from such types or portions having a characteristic 
appearance in common. 
