FORMS FOE SPECIFICATIONS, ETC., FOR ROAD MATERIALS. 



11 



specifications. Stone or gravel screenings shall be sampled for 



grading in accordance with the method described on page , 



paragraphs , of these specifications. 



Tests of the physical properties of stone shall be made in ac- 

 cordance with the method described or referred to on page 



of these specifications, test No. Tests of the grading of 



screenings shall be made in accordance with the method described 

 or referred to on page of these specifications, test No. 



Methods of 



testing. 



SPECIFICATION FOR COMBINATIONS OF DUSTLESS SCREENINGS AND SAND FOR 

 FINE AGGREGATE FOR PORTLAND-CEMENT CONCRETE WEARING SURFACE. 



The fine aggregate may be composed of a combination of dust- 

 less screenings and sand, but shall contain not more than * 



per cent, by volume, of dustless screenings. 



The dustless screenings shall consist of material obtained by 

 crushing hard, durable rock, or gravel, all of which when dry 

 shall pass a revolving screen having circular openings three- 

 eighths-inch in diameter. They shall be free from lumps of clay 

 and, at the time of use, from lumps or crusts of hardened ma- 

 terial. 



The sand shall consist of clean, hard, durable, uncoated par- 

 ticles, preferably siliceous, well graded from coarse to fine, and 

 free from lumps of clay and all organic matter. 



If the dustless screenings are produced from rock, the rock 

 shall meet the following requirement : 



Per cent of wear not more than 



(or French coefficient not less than ) 



The dustless screenings shall be well graded from coarse to 

 fine, and, when tested by means of laboratory screens and sieves, 

 shall meet the following requirements : 



Per cent. 



Passing 1/4-inch screen ■. not less than 



Passing 20-mesh and retained on 50-mesh 



sieve to 



Passing 100-mesh sieve not more than 5 



The mixture of screenings and sand shall contain no particles 

 which would not pass a revolving screen having circular openings 

 not greater than three-eighths-inch in diameter. When tested by 

 means of laboratory screens and sieves it shall meet the follow- 

 ing requirements: 



Per cent. 



Passing 1/4-inch screen not less than 



Passing 20-mesh and retained on 50-mesh 



sieve to 



f Total passing 50-mesh sieve not more than 



^Passing 100-mesh sieve not more than 



Not more than per cent by weight shall be removed by 



the elutriation test. 



General. 



Physical prop- 

 erties, dustl ess 

 screenings. 



Grading of 

 dustless screen- 

 ings. 



Grading of 

 mixture. 



* The figure 50 is recommended. 



t It is recommended that 25 per cent be specified as the amount per- 

 mitted to pass a 50-mesh sieve. 



t It is recommended that 5 per cent he specified as the quantity per- 

 mitted to pass a 100-mesh sieve. 



