SAMPLING AND TESTING HIGHWAY MATERIALS 81 
23. The specimens shall he immersed for 72 hours in water 
having a temperature of 18° to 24° C. (65° to 75° F.) and then 
weighed as specified in section 12. 
24. When the specimens (either from the absorption test or 
from a specially prepared series) have been weighed after satu- 
ration with water, they shall be returned to the water and kept 
immersed till the freezing 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, 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 artificial freezing 
apparatus is employed, the apparatus shall have sufficient heat- 
absorbent capacity to enable the temperature of the freezing 
chamber to be brought to — 10° C. (+14° F.) or below within 
30 minutes after the introduction of the specimens. The tem- 
perature 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 condi- 
tions in excess of this requirement shall be considered as with- 
out significance. 
At the conclusion of freezing under the specified conditions, 
the crate of specimens shall be withdrawn and at once immersed 
in water at 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 tempera- 
ture 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. 
25. Failure under the freezing and thawing treatment shall be 
considered to be reached when : 
(a) The specimens show superficial disintegration or spalling 
with loss of weight of more than 5 per cent of the initial dry 
weight ; or 
(Z>) The specimens are badly cracked in other than lamination 
planes; or 
(c) The specimens show evident serious loss of structural 
strength. 
Note. — Routine tests for control of quality and for basis of ac- 
ceptance of pipe shall preferably be made at the manufacturer's plant. 
In addition to these tests the plants should be inspected at fre- 
quent intervals by a competent engineer who should note all the de- 
tails of manufacture and take samples for test of all materials be- 
ing used. 
TEST FOR THE AMOUNT OF SPELTER COATING ON 
CULVERT METAL. 
1. The amount of spelter coating shall be determined by one 
of the following methods: 
2. (a) Antimony hydrochloric acid method. — Use three 2i by Antimony 
2^-inch pieces, weighed together to three decimal places. They hydrochloric 
are then immersed separately for one-half minute in hydrochloric acid method. 
acid of specific gravity 1.20 to which has been added 5 cubic centi- 
meters of antimony chloride solution prepared by dissolving 20 
grams of antimony trioxide in 1,000 cubic centimeters of hydro- 
chloric acid of specific gravity 1.20. The pieces are scrubbed with 
a brush under running water, dried, and again weighed. About 
100 cubic centimeters of the hydrochloric acid will usually be suffi- 
67090°— 24 6 
