VITKIFIED BKICK PAVEMENTS FOR COUNTRY ROADS. 31 



the marks of the roller and a grout of water and rock dust flushes ahead of the 

 roller. 



After the base is completed, as above specified, no materials or traffic shall be 

 placed or allowed upon it for at least twenty-four (24) hours. 



Crushed stone for the base shall be newly broken, of uniform quality through- 

 out, and free from tailings, slaty and flat fragments, soft or disintegrated stone, 

 dirt, or other objectionable matter. 



The following designations and sizes shall obtain : 



Screenings. — All that portion of the product of the crusher which will pass 

 through a screen having one (1) inch circular openings, including the dust of 

 fracture. 



No. 2 stone. — All that portion of the product of the crusher which will be re- 

 tained on a screen having one (1) inch circular openings and will pass through 

 a screen having circular openings not less than two (2) inches nor greater than 

 two and one-fourth (2?) inches in diameter. 



No. 1 stone. — All that portion of the product of the crusher which will be re- 

 tained on a screen having circular openings not less than two (2) inches nor 

 greater than two and one-fourth (2J) inches in diameter, and will pass through 

 a screen having circular openings not less than three (3) inches nor greater 

 than three and one-half (3|) inches in diameter. 



A sample of the stone when subjected to tbe hardness, toughness, and abra- 

 sion tests, as described in United States Office of Public Roads Bulletin No. 44, 

 shall satisfactorily meet the following requirements: Hardness not less than 

 ,* toughness not less than ,* and per cent of wear not more than } 



APPENDIX B. 

 Method for Inspecting and Testing Paving Brick. 2 



The quality and acceptability of paving brick, in the absence of other special 

 tests mutually agreed upon in advance by the seller on the one side and the 

 buyer on the other side, shall be determined by the following procedure, viz : 



(1) The rattler test, for the purpose of determining whether the material as 

 a whole possesses to a sufficient degree, strength, toughness, and hardness; 



(2) Visual inspection, for the purpose of determining whether the physical 

 properties of the material as to dimensions, accuracy and uniformity of shape 

 and color are in general satisfactory, and for the purpose of culling out from 

 the shipment individually imperfect or unsatisfactory brick. 



The acceptance of paving brick as satisfactorily meeting one of these tests 

 shall not be construed as in any way waiving the other. 



SECTION I.— THE RATTLER TEST. 



THE SELECTION OF SAMPLES FOR TEST. 



Item 1. Place of sampling. — In general where a shipment of brick involving a 

 quantity of less than 100,000 is under consideration, the sampling may be done 

 either at the brick factory prior to shipment, or on cars at their destination, or 



1 Values for hardness, toughness, and per cent of wear should be fixed with a view to 

 securing the very best stone locally available, and not merely to exclude stone of a known 

 unsatisfactory nature. 



2 Recommended by subcommittee on paving brick of the American Society for Testing 

 Materials. 



