RESULTS OF PHYSICAL TESTS OF HOCK, L916 AND L917. 29 



Table IV. — General limiting test vUluesfor broken stom 



Type of construction. 



Water-bound macadam, plain or with 

 dust palliative treatment. 



Macadam with bituminous carpet 



Bituminous macadam with seal coat . . . 



Bituminous concrete 



Binder course for sheet asphalt or 

 Topeka type. 



Portland cement concrete 



Stone paving block 3 



Broken-stone foundations 



Cement-concrete foundations 



Traffic. 1 



(Ughl 



^Moderate 



| Heavy 



Lighl io moderate.. 



Moderate to heavy . 

 flight to moderate.. 

 (Moderate to heavy. 



Any 



Moderate to heavy . 

 Any 



■...do 





i n act 



coefficient 



of wear. 



5 to 8 



9 to 15.... 

 Hi or over. 

 5 or over. 

 7 or over.. 

 7 or over . 



10 or over. 

 7 or over. 



7 or over. . 



8 or over.. 





r, loo 



10 to 18.... 

 19 or over.. 



6 or over. . . 

 LOoro ei 



7 or over. . 

 L3oi o i i 



6 or over. .. 



8 or over.. . 



9 or over.. . 



3 or over.. . 



EJardnc 



10 to 17. 

 17 or over, 





l6orovi r. 



1 Light traffic is assumed as less than 100 vehicles per day, moderate traffic between 100 and 250 vehicle , 

 and heavy traffic over 250 vehicles per day. 



2 Numerous tests have shown that limits for hardness are unnecessary if the material possesses the re- 

 quired French coefficient of wear and toughness. 



3 Crushing strength, 20,000 pounds or over per square inch, is frequently required. 



Cementing values should in all cases show over 25 if matei Lai is to 

 be used in water-bound macadam construction. 



Granites, gneisses, schists, sandstones, and quartzites should not, 

 in general, be used in the wearing course of water-bound macadam 

 roads. Shales and slates should never be used in this connection. 

 Cementing value tests have therefore been discontinued on these 

 materials. 



For further details and explanation of results in this table and also 

 for tests on all materials to January 1, 1916, see United States 

 Department of Agriculture Bulletin No. 370. 



