32 
U. S. DEPT. OF AGRICULTURE 
ib) Each mold shall be provided with a base plate having a plane surface 
and made of nonabsorbent material. This plate shall be large enough in diam- 
< t( r to properly support the mold without leakage. Plate glass or planed metal 
are satisfactory for this purpose. A similar plate should be provided for cover- 
ing the top surface of the test specimen when molded. 
(o) Suggestions for suitable molds are shown in Figures 9, 10. and 11. 
4. (a) Concrete for the test specimens shall be taken immediately after it 
has been placed in the work. All the concrete for each sample shall be taken 
from one place. A sufficient number of samples — each large enough to make 
one test specimen — shall be taken at different points so that the test specimens 
made from them will give a fair average of the concrete placed in that portion 
of the structure selected for tests. The location from which each sample is 
Taken shall be noted clearly for future reference. 
(&) In securing samples, the concrete shall be taken from the mass by a 
shovel or similar implement and placed in a large pail or other receptacle, for 
8 7 Bolt 
4* i "Steel Band 
drawn seamless steel 
Side View. 
tubing ; £ "wails-, make narrow slit along one 
element with ^ slitting saw. May also use 
6 "steel water-pipe , machined inside ; slit 
along one element, so thai when closed will 
give 6" inside diameter. 
Fig. 9. — Type of mold 
transporting to the place of molding. Care shall be taken to see that each test 
specimen represents the total mixture of the concrete from a given place. Dif- 
ferent samples shall not be mixed together but each sample shall make one 
specimen. 
5. (a) TLe pails or other receptacles containing the samples of concrete shall 
be taken as quickly as possible to the place selected for molding test speciniens. 
To offset segregation of the concrete occurring during transportation, each 
sample shall be dumped into a nonabsorbent water-tight receptacle and, after 
slight mixing, immediately placed in the mold. 
(b) The test specimens shall be molded by placing the concrete in the mold 
in layers 3 to 4 inches in thickness. Each layer shall be puddled with 25 strokes 
with a %-inch rod 24 inches in length bullet-pointed at the lower end. After 
puddling the top layer, the surface concrete shall be struck off with a trowel 
and covered with the top cover plate which may later be used in capping the 
rest specimen. 
