40 
BULLETIN 121G, U. S. DEPARTMENT OF AGRICULTURE. 
METHOD OF SAMPLING AND TESTING BUILDING BRICKS 
FOR MASONRY CONSTRUCTION. 
I. SAMPLING. 
1. For the purpose of testing, bricks shall be selected by an 
experienced person so as to represent the commercial product. 
All bricks shall be carefully examined and their condition noted 
before being subjected to any kind of test. For the purpose of 
3ting, 1" bricks will he required; they shall be thoroughly 
(iricd to constanl weight Id a suitable even at a temperature of 
from 225° P. (107° C.) to 250° F. (121° C). 
II. PHYSICAL TESTS. 
Absorption. 2. (a) At least five dry bricks shall be weighed and completely 
submerged in water ;it a temperature between 60° and 80° F. 
(15° and 27° ('.). The water shall be heated to boiling within 
one hour, boiled continuously for five bours and then allowed to 
cool to a temperature between 60° and so D p. (15° and 27 C). 
The bricks shall then be removed, the surface water wiped off 
with a damp cloth, and the bricks quickly weighed. 
(b) The percentage of absorption shall be computed on the 
dry weight, according to the relation: 
, , 100(5-^) 
Percentage of absorption= -j 
where A=weight of dry bricks and B=we'ight of saturated bricks. 
Compression 3. (a) Compression tests shall he made on at least five half 
test. bricks, previously dried, each taken from a different brick. The 
half bricks shall be prepared either by sawing or cutting upon a 
yielding bed with a sharp mason's chisel, which shall be the 
lull width of the brick. The specimens shall be tested on edge. 
To secure a uniform bearing in the testing machine, the edge 
surfaces shall be bedded in a thin coat of calcined gypsum 
(plaster of Paris) spread upon plate glass previously coated 
with a film of oil. Before applying the calcined gypsum (plaster 
of Paris), the bearing surface of the bricks shall receive a coating 
of shellac. The bricks shall he pressed firmly upon the surface. 
making the layer as thin as possible, and shall be permitted to 
remain undisturbed until set. The depression of recessed or 
paneled bricks shall be filled with neat Portland cement mortar, 
which shall stand at least 24 hours before testing. 
(&) The machine used for the compression tests shall be 
equipped with a spherical bearing block kept thoroughly lubri- 
cated to insure accurate adjustment, which should be made by 
band under a small initial load. During the test the beam of 
the testing machine shall be kept constantly in a floating position. 
(c) The breaking load shall be divided by the area in com- 
pression and the results reported in pounds per square inch. 
4. (a) At least five brick, previously dried, shall be tested, 
laid flatwise, with a span of 7 inches, and with the load applied 
at mid span. 
(b) The modulus of rupture shall be computed in pounds per 
square inch by the following formula: 
R= 
3JTT 
2 bd 2 
in which J=the distance between supports in inches, b=the 
breadth and d=depth <>\' the brick in inches, and ir = the load 
in pounds at which the brick failed. 
Record form. 5. In recording the results of the tests the type Of brick shall 
be defined, whether Stiff-mud, soft -mud. dry-pressed, repressed. 
sand-lime or other types. It is recommended that the data ob- 
tained be recorded as indicated on the accompanying " Labora- 
tory record." 
