SPECIFICATIONS FOR NONBITTIMIlSrOUS EOAD MATERIALS. 

 SPECIFICATION RBC-2. 



Broken Stone, Sand, and Filler for Coarse Aggregate Bituminous Concrete 

 Wearing Course. 



BROKEN STONE. 



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

 schist, shale, and slate, free from thin or elongated pieces, soft or dis- 

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

 or as a coating on the stone. 



The stone shall meet the following requirements : Physical 



French coefficient of wear, not less than . 8 Properties. 



Toughness, not less than 8 



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

 means of laboratory screens, will meet the following requirements : 



Per cent. 



Passing i-inch screen, not less than 95 



Retained on J-inch screen, not less than 85 



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

 of laboratory screens, will meet the following requirements : Aggrtigate. 



Per cent. 



Passing 1-inch screen, not less than 95 



Total passing |-inch screen 25 to 75 



Retained on i-inch screen, not less than 85 



SAND. 



The sand for fine aggregate shall be composed of sound, durable stone General. 



particles, free from a coating of clay or loam. 



When tested by means of laboratory screens the sand shall meet the Grading. 



following requirements : 



Per cent. 



Passing i-inch screen 100 



Total passing 40-mesh sieve 80 to 70 



Retained on 200-mesh sieve, not less than 90 



MINERAL FILLER. 

 The mineral filler shall consist of limestone dust, dolomite dust, Port- General. 



land . cement, or natural cement. It shall be free from foreign or other 



objectionable material. 



When tested by means of laboratory sieves, the mineral filler shall meet Fineness. 



the following requirements : 



Per cent. 



Passing 30-mesh sieve 100 



Total passing 200-mesh sieve, not less than 65 



Tests of the physical properties of the rock and of the size or mechan- Methods of 



ical analysis of broken stone, sand, and mineral filler shall be made in Testing. 



accordance with the following methods : 



1. French coefficient of wear, U. S. Department of Agriculture Bulletin 



347, p. 5. 



2. Toughness, U. S Department of Agriculture Bulletin 347, p. 15. 



3. Size of broken stone, U. S. Department of Agriculture Bulletin 555, 



p. 32. 



4. Mechanical analysis of sand and mineral filler, U. S. Department of 



Agriculture Bulletin 555, p. 33. 



This specification is intended to cover the mineral constituents of 

 a roughly proportioned bituminous concrete consisting of from 45 

 to 60 per cent brolien stone coarse aggregate, from 30 to 45 per cent 

 sand (fine aggregate), from 3 to 5 per cent mineral filler, and from 

 5 to 8 per cent bitumen. Such a concrete is similar in character 

 to that described under Specification RBC-1, but is a closer mix. 

 It should preferably be placed upon a cement concrete foundation 

 58683°— 18— Bull. 704 2 



