General. 



Size. 



Method of 

 Testing. 



BULLETIlSr 704, U, S. DEPARTMENT OF AGRTCULTUEE. 



SPECIFICATION RS— 2. 



Fine Broken Sttone or O ravel for Bituminous Surface Treatment. 



The broken stone or gravel shall consist of clean hard tough durable 

 stone, free from soft or disintegrated particles, dirt, or other objectionable 

 matter. 



When tested by means of laboratory screens it shall meet the following 

 requirements : 



Per cent. 



Passing J-inch screen, not less than 85 



Retained on J-inch screen, not less than 85 



Tests of the size of broken stone or gravel shall be made in accord- 

 ance with the following method : 



Size, U. S. Department of Agriculture Bulletin 555, p. 32, 



This specification provides for a product to be used as cover for 

 a bituminous material applied to a road surface. For this pur- 

 pose 1 cubic yard should cover from 50 to 150 square yards of 

 treated road surface, depending upon tlie amount of bituminous 

 material which has been applied per square yard. Under traffic 

 it is expected to produce, in combination with the bituminous ma- 

 terial, a thin wearing mat or carpet. It may be considered as an 

 alternate for Specification RS-1 and preferable to the latter when 

 the treatment of bituminous material is less than J gallon per 

 square yard. 



SPECIFICATION RB-1. 



Broken Stone for Bituminous Macadam. 



General. 



Physical 

 Properties. 



Screenings. 



Chips. 



Top Course 

 Stone. 



The broken stone shall consist of angular fragments of rock, excluding 

 granite, gneiss, sandstone, quartzite, schist, shale, and slate, of uniform 

 quality throughout, free from thin or elongated pieces, soft or disinte- 

 grated stone, dirt, or other objectionable matter, occurring either free or 

 as a coating on the stone. 



The stone shall meet the following requirements : 



French coefficient of wear, not less than 7 



That portion of the product of the crusher, including the dust of 

 fracture, which, wlien tested by means of laboratory screens, will meet 

 the following requirements : 



Per cent. 



Passing 1-inch screen, not less than 95 



Total passing i-inch screen 40 to 80 



That portion of the product of the crusher which, when tested by 

 means of laboratory screens, will meet the following requirements : 



Per cent. 



Passing 1-lnch screen, not less than 95 



Retained on 3-inch screen, not less than 85 



That portion of the product of the crusher which, when tested by 

 means of laboratory screens, will meet the following requirements : 



Per cent. 



Passing 2-inch screen, not less than 95 



Total passing IJ-lnch screen ' 25 to 75 



Retained on 1-inch screen, not less than 85 



