50 DEPARTMENT" BULLETIN 12 16, U. S. DEPT. OF AGRICULTURE 
19. When the specimens (either from the absorption test or from a specially 
prepared series) have been weighed after saturation with water they shall be 
returned to the water and kept immersed till the freezing test is begun. For 
freezing they shall be placed with their concave faces upward in water-tight 
metal trays, suitably mounted in a rigid metal crate, 30 and immersed in ice 
water until the specimens have attained substantially the temperature of the 
water, after which the water shall be drawn down to a depth of one-half inch 
in each tray. The crate shall then be lifted as a whole, without disturbing the 
specimens, and placed in the freezing apparatus. 
Freezing shall be performed in a quiet atmosphere, free from perceptible 
natural or artificial currents. If the artificial freezing apparatus is employed 31 
the apparatus shall have sufficient heat-absorbent capacity to enable the tem- 
perature of the freezing chamber to be brought to —10° C (+14° F.) or 
below within 30 minutes after the introduction of the specimens. The tempera- 
ture in the freezing apparatus shall not fall lower than — 20° C. ( — 4° F.). 
The freezing shall be continued until the water in the trays is frozen solid. 
Exposure to freezing conditions in excess of this requirement shall be consid- 
ered as without significance. 
At the conclusion of freezing under the specified conditions the crate of speci- 
mens shall be withdrawn and at once immersed in water at a temperature of 
18° to 24° C. (65° to 75° F.) in a special receptacle of proper size. Heating 
shall be continued so that the water will regain the required temperature as 
soon as practicable after the specimens are immersed. A temperature of 18° 
to 24° C. (65° to 75° F.) shall then be maintained for not less than two hours. 
At the conclusion of the thawing treatment the crate of specimens shall be 
inspected, and the condition of each sample after each thawing shall be noted 
in the records. 
34. METHOD OF SAMPLING AND TESTING DRAIN TILE 
(A. S. T. M. standard method </). serial designation C 4-24. sections 8 to 30, inclusive, 
except as indicated. See p. 1) 
8. The specimens of tile shall all be selected at the factory or at the shipping 
destination, or at the trench, at the option of the purchaser. The selection 
shall be made by a competent inspector employed by the purchaser. The in- 
spector shall divide the tile into subclasses if lack of uniformity in any import- 
ant particular warrants such division, and shall select enough representative 
specimens of tile from each subclass for a complete set of standard physical 
tests. 
9. A standard physical test shall comprise tests of five individual tiles. 
►Specimens of tile may he selected by the inspector in such number as he judges, 
necessary to determine fairly the quality of all the tile. The manufacturer or 
other seller shall furnish specimens of tile without separate charge up to 0.5 
per cent of the whole number of tile, and the purchaser shall pay for all in 
excess of that percentage at the same rate as for other tile. 
(A) STRENGTH TESTS OF DRAIN TILE 
10. The specimens of tile shall be unbroken, full-size tile. 
11. The walls of the tile shall, at the time of testing, be as thoroughly wet 
as will result from completely covering with hay, cloth, or similar absorbent 
material, and keeping the covering wet for not less than 12 hours. 32 
12. No specimen of tile shall be exposed to water or air temperatures lower 
than 40° F. from the beginning of wetting until tested. Frozen title shall be 
completely thawed before the wetting begins. 
13. Each specimen of tile shall be weighed on reliable scales just prior to 
testing, and the weights shall be reported. 
30 A satisfactory type of freezing apparatus is illustrated in connection with A. S. T. M. 
method, serial designation C 4-24 (.',). (See figs. 22 and 23.) 
31 Artificial freezing will generally be necessary. It may be conducted in a commercial 
refrigerating room at 0° F. temperature or in an artificial freezing box similar to the 
one shown in Figure 23, in which 0° F. temperatures can readily be produced by the use 
of salt and ice. 
32 In the case of routine testing, the preliminary wetting of the walls of the tile may be 
omitted. 
