RESULTS OF PHYSICAL TESTS OF KOCK, 1916 AND 1917. 29 
Table IV. — General limiting test values for broken stone. 
Type of construction. 
Water-bound macadam, plain or with 
dust palliative treatment. 
Macadam with bituminous carpet 
Hit ominous macadam with seal coat . . . 
Bituminous concrete 
Hinder course for sheet asphalt or 
Topeka type. 
Port land cement concrete 
SI one paving block 3 
Broken-stone foundations 
Cement-concrete foundations 
Traffic. 1 
[Light 
{Moderate 
I Eeayy 
Light to moderate. 
Moderate to heavy . 
/Light to moderate.. 
\Moderate to heavy . 
Any 
Moderate to heavy . 
Any .*.. 
►...do 
Limiting values. 
French 
coefficient 
of wear. 
5to8 
9 to 15 
16 or over.. 
5 or over . . 
7 or over. . . 
7 or over . . 
10 or over.. 
7 or over.. 
7 or over. . . 
8 or over... 
3 or over... 
Toughness. 
5to9 
10tol8.... 
19 or over.. 
5 or over. . . 
10 or out.. 
7 or over. . 
13 or over. . 
6 or over. . . 
8 or over. . . 
9 or over. . . 
3 or over... 
Hardness. 
10 to 17. 
It or over. 
17 or over. 
( 2 ) 
(«) 
( 2 ) 
16 or over. 
8 or over. 
1 Light traffic is assumed as less than 100 vehicles per day, moderate traffic between 100 and 250 vehicles, 
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 material 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. 
