30 BULLETIi^ 373^ U. S. DEPAETMEXT OF AGEICULTTJEE. 



than ten (10) per cent; but chipped brick, if otlier\Yise satisfactory, may be 

 used in obtaining tlie 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, lioio- 

 evcr, 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 descx'ibed 

 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) degi'ees centigiade of a No. 2 needle acting five (5) seconds 

 under a weight of fifty (50) grams shall not exceed ten (10) millimeters. 



CONSTEUCTIOJV. 



Concrete base. — ^TJpon 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 thoi'oughly 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. AYheelbarrows 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 



