METHODS OF SAMPLING AND TESTING HIGHWAY MATERIALS 41 
(c) The speed of the moving head of the testing machine, dining the appli- 
cation of the load, shall not be more than 0.05 inch per minute. 
id) During the test the beam of the testing machine shall be kept constantly 
in a floating position. 
7. The compressive strength in pounds per square inch shall be reported as 
the total maximum load. W, in pounds, indicated by the testing machine, 
divided by the area, A, in square inches, of the minimum section of the speci- 
men perpendicular to the line of application of the load. 
The compressive strength in pounds per square inch shall be calculated from 
the formula : 
W 
Compressive strength =■— - 
A 
FLEXURE TEST 
APPARATUS 
8. (a) Any form of standard testing machine with knife edges as described 
in paragraph (&) may be used for the flexure test. 23 
(&) Knife edges shall be straight and have full contact with the specimen 
or beaiing plate, and they shall have a length at least equal to the width of 
the brick to be tested. Their bases shall be so curved or rounded as to permit 
14" - 
Side Elevation. 
Fig. 13. — Knife edges use in testing brick 
End View. 
free movement of the working edges, both longitudinally and transversely. 
The use of knife edges of the type shown in Figure 13 is recommended, although 
other types may be used which will provide free movement and at the same 
time insure full and even bearing at all times during the test. 
TEST SPECIMEN 
9. The test specimen shall be a whole brick. 
10. Flexure tests shall be made on at least five whole bricks. 
PROCEDURE 
11. (a) A test specimen brick shall be placed flatwise on the knife edges 
with a span of 7 inches and the load applied at midspan. 
23 Portable apparatus properly calibrated may be used. 
