30 BULLETIN 373, U. S. DEPARTMENT OF AGRICULTURE. 
than ten (10) per cent; but chipped brick, if otherwise satisfactory, may be 
used in obtaining the half brick for breaking courses and the necessary pieces 
of brick for closures. The brick shall not be salt glazed or otherwise arti- 
ficially glazed. Not less than five (5) samples of ten (10) brick each will 
be selected from each kiln or shipment and subjected to the rattler test recom- 
mended to the American Society for Testing Materials by its subcommittee on 
paving brick; one sample from what appears to be the softest brick, which 
shall not lose of its weight more than twenty-four (24) per cent; one sample 
from what appears to be the hardest brick, which shall not lose of its weight 
less than sixteen (16) per cent or more than twenty-four (24) per cent; and 
three samples representing an average of the kiln or shipment, which shall 
not lose of their weight more than twenty-two (22) per cent: Provided, how- 
ever, That if the softest brick lose less than twenty-four (24) per cent, the 
permissible minimum loss of the hardest brick will be reduced a like amount. 
If the kiln or shipment of brick should fail to meet, the above requirements — 
and it is fair to assume that it would meet them if not more than ten (10) 
per cent were culled — then the contractor may, at his option, regrade the brick. 
When the regrading is complete the kiln or shipment will be resampled and 
retested as under the original conditions, and if it fails to meet any of the 
above requirements it will be finally and definitely rejected. Sampling will 
be done at the factory prior to shipment or from cars when placed on siding 
at destination, and brick satisfactorily passing the rattler test will not be 
rejected as a whole, but will be subject to such culling as may be necessary 
to meet all of the above requirements. The brick shall be carefully unloaded 
from cars and wagons by hand and neatly piled along the work in such manner 
that they will be clean and in proper condition to be laid in the pavement 
when desired. 
Bituminous filler for expansion cushion. — The bituminous filler for the ex- 
pansion cushion between the brick pavement and the curb shall be a blown-oil 
asphalt. It shall be soluble in chemically pure carbon disulphide to at least 
ninety-nine (99) per cent, and when tested by the cube method, as described 
in United States Department of Agriculture Bulletin No. 314, its melting point 
shall not be less than ninety (90) degrees centigrade and not more than one hun- 
dred and ten (110) degrees centigrade. The penetration at zero (0) degrees 
centigrade of a No. 2 needle acting one (1) minute under a weight of two hun- 
dred (200) grams shall be not less than two (2) millimeters. The penetration 
at forty-six (46) degrees centigrade of a No. 2 needle acting five (5) seconds 
under a weight of fifty (50) grams shall not exceed ten (10) millimeters. 
CONSTEUCTION. 
Concrete base. — Upon the subgrade prepared as herein specified shall be 
laid a concrete base of the width and thickness shown on the plans. The sub- 
grade shall be wet but not muddy when the concrete is placed upon it. The 
concrete shall be composed of the following materials, by volume: One (1) 
part of cement, three (3) parts of sand, and five (5) parts of gravel, crushed 
stone, or crushed slag, and sufficient water to form a quaky mass, and shall 
be thoroughly mixed in a machine mixer of the batch type so constructed and 
operated that the thorough mixing of the materials will be assured. The con- 
crete shall be so delivered to its place on the subgrade as not to cause or permit 
any separation of the materials. Wheelbarrows or other devices used for 
measuring the materials shall be of uniform capacity. The concrete shall 
be deposited in place immediately after it is mixed and shall be well compacted 
as fast as it is placed. The top surface shall be smoothed by troweling with 
