26 BULLETIN 246, U. S. DEPARTMENT OF AGEICULTUEE. 



kiln marks more than one-sixteenth (^g) 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 

 (s) nor more than one-fourth (i) 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 ($) 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 eushion. — 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 (09) 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 base. — Upon the subgrade prepared as herein specified shall be laid 

 a concrete base of the width and thickness shown on the plans. The subgr;i<lo 

 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 



