METHODS OF SAMPLING AXT- TESTING HIGHWAY MATERIALS 49 
load shall be applied continuously until the ultimate strength of the pipe is 
reached. The load at ultimate strength and also when the first crack appears 
shall be observed and recorded. 
8. In testing pipe which is " out of line " the lines of the bearings chosen shall 
be from those which appear to give the most favorable conditions for fair test. 
ABSORPTION TESTS (CONCRETE AND VITRIFIED CLAY PIPE) 
9. Nor less than three separate test specimens from each of five separate 
pipe shall be taken a> a " standard sample " for the absorption test. Of the 
three specimens from each pipe, one shall be taken from one end. another from 
the opposite end. and the third shall be taken from the middle portion of the 
pipe. Each specimen shall be of from 12 to 20 square inches in area, measured 
upon the exterior or convex side, and shall be as nearly square as the nature 
of the material will readily permit. The specimens shall be obtained by break- 
ing the pipe, and shall be apparently sound, solid piece- of the wall of the pipe, 
and shall not show cracks or fissures or shattered edges due to the shock of 
breaking or cutting. The specimens may be obtained from the broken pieces 
of the pipe used in the strength test, if the restrictions as to the *ize and loca- 
tion of the specimens can be duly observed. The specimens shall be so marked 
as to permit the identity of each one to be ascertained at any stage of the test. 
10. Preparatory to the absorption test, all specimens shall be weighed and 
then dried in a drier or oven at a temperature of not less than 110° C. (230° F. i 
for not less than three hours. After removal from the drier the specimens shall 
be allowed to cool to a temperature of 2it c to 2.3 ('. (68 e to 77 F.) and 
reweighed. If the specimens were apparently dry when taken and the second 
weight closely checks the first, the specimens shall lie considered dry. If the 
specimens were known to be wet. when taken they shall be placed in the drier 
for a further drying treatment of two hours and reweighed. If the third weight 
checks the second the specimens shall be considered dry. In case of any doubt. 
the specimens must be redried for two-hour periods until check weights are 
obtained. 
11. The balance used shall be sensitive to 0.5 grams when loaded with 1 kilo- 
gram, and weighings shall be read at least to the nearest gram. Where other 
than metric weights are u<ed the same order of accuracy must be obtained. 
12. In reweighing after immersion, the specimens shall be removed from the 
water, not allowed to drain for more than one minute, the superficial water 
removed by towel or blotting paper, and the specimens at once put upon the 
balance. 
13. Specimens after weighing shall be placed in a suitable woven-wire recep- 
tacle, packed tightly enough to prevent jostling, covered with distilled water or 
rain water, raised to the boiling point and boiled for five hours, and then cooled 
in water to a final temperature of 10° to 15° C. (50° to 59 c F.). 
14. The test results shall lie calculated as percentages of the initial dry 
weight, carried to the nearest first decimal place. The results shall be reported 
separately for each individual specimen, together with the mean of the 15 or 
more specimens comprising the standard sample. The maximum and the minimum 
single observations entering into the mean, and the variation between the maxi- 
mum and the minimum of the three specimens of each pipe represented in th* 
standard sample. 
FREEZING AND THAWING TESTS (CONCRETE AND VITRIFIED 
CLAY PIPE) 
15. The test specimens employed in making the freezing and thawing test 
shall be another set selected as specified in section 9. 
16. The specimens shall be dried a< specified in section 10. 
17. The same scales and weights as are specified in section 11 for the absorp- 
tion test or < thers of equivalent sensitiveness and accuracy shall be employed 
for the weighings required in the freezing and thawing test. The same pro- 
cedure in weighing and reweighing as specified in section 11 shall be used. 
i8. The specimens shall be immersed for 72 hours in water having a tem- 
perature of iv : to 24 c C (65 t< 75° F.) and then weighed as specified in 
section 11. 
m A S. T M. standard specification, serial designation C 4-2-i 
roa A. S. T. M. sppoilkar: - I UH-it:ij;ition C 4-1*4 i)i. 
104022° — 28 1 
