26 BULLETIN 246, U. S. DEPARTMENT OF AGRICULTURE." 
kiln marks more than one-sixteenth (is) inch in depth and shall be free from 
cracks. The brick shall have not less than four (4) and not more than six (6) 
lugs, all on one side of the brick, such that when the brick are properly laid in 
place in the pavement the joints between them will be not less than one-eighth 
(i) nor more than one-fourth (J) inch in width. The name or trade-mark of the 
manufacturer, if shown on the brick, must be recessed and not raised. If the 
edges of the brick are rounded, the radius shall not exceed one-eighth ( J ) inch. 
The brick must not be chipped in such a manner that the wearing surface 
is not intact or that the lower or bearing surface is reduced in area more 
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 artificially 
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 recommended 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, however, That if 
the softest brick lose less than twenty-four (24) per cent, the permissible mini- 
mum loss of the hardest brick will be reduced a like amount. If the kiln or ship- 
ment 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) percent 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 expan- 
sion 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 Office of Public Roads Bulletin No. 38, its melting point shall not 
be less than ninety (90) degrees centigrade and not more than one hundred 
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 hundred (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. 
CONSTRUCTION. 
Concrete oase. — Upon the subgrade prepared as herein specified shall be laid 
a concrete base of the width and thickness shown on the plans. The subgrade 
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 
