40 DEPARTMENT BULLETIN 1216, IT. S. DEPT. OP AGRICULTURE 
COMPRESSION TEST 
APPARATUS 
2. Any form of standard testing machine may be used for the compression 
rest, together with a spherical bearing block large enough entirely to cover the 
specimen. 
TEST SPECIMEN 
3. The test specimen shall consist of a half brick. 2 - Any method which will 
produce a specimen with approximately plane and parallel ends, without shat- 
tering the specimen, may be used. 
4. A half brick to be used for the compression test shall be prepared as 
follows : The two surfaces intended to receive the load from the testing ma- 
chine shall receive a thin coating of shellac and be allowed to dry thoroughly. 
One of the shellacked bearing surfaces shall then receive a thin coat of a neat 
mortar of calcined gypsum (plaster of Pans). This mortared face of the 
Cross — \Head of 
Testing Machine 
Spherical Seat 
Center of 
Spherical Surface— 
Spherical Bearing Block 
Bedding Material 
ne- half Brick 
Bedding Material 
Fig.- 12. — Special bearing block for use in testing brick 
specimen shall then be pressed on plate glass or a machined metal plate, pre- 
viously oiled or covered with waxed paper, and the bedding material allowed 
to harden. This procedure shall be repeated with the other shellacked surface. 
Care shall be taken that the opposite faces so coated with bedding material 
shall be parallel. Depressions or recessed or paneled bricks shall be filled with 
neat Portland-cement mortar, which shall stand at least 24 hours before testing. 
5. Compression tests shall be made on at least five half-brick test specimens 
from different bricks. 
PROCEDURE 
6. (a) The half-brick test specimen shall be tested, placed flat. 
(b) The bearing Mock shall be used on top of the test specimen in vertical 
testing machines. The center of the sphere of the bearing block shall be used 
in contact with the top bearing surface of the specimen, and in the vertical 
axis of the specimen. (Fig. 12.) The spherical bearing block shall be kept 
thoroughly lubricated to insure accurate adjustment, which should be made 
by hand under a small initial load. 
-- This permits thn use of a suitable half brick from the flexure test. 
