SPECIFICATIONS FOR NONBITUMINOUS ROAD MATERIALS. Tal 
Tests of the size or mechanical analysis of broken stone, sand, and Methods of 
mineral filler shall be made in accordance with the following methods: Testing. 
1. Size of broken stone, U. S. Department of Agriculture Bulletin 555, 
p. 32. 
2. Mechanical analysis of sand and mineral] filler, U. S. Department of 
Agriculture Bulletin 555, p. 33. 
3. Grading of total. mineral aggregate, U. S. Department of Agricul- 
ture Bulletin 555, pp. 32 and 33. 
This specification is intended to cover the mineral constituents 
and grading for bituminous concrete of a modified Topeka, or 
stone-filled, sheet asphalt type. It is so drawn that from 10 to 50 
per cent of broken stone will be required and the mixture of very 
fine broken stone and sand will possess a satisfactory sheet asphalt 
grading. Such an aggregate will carry from 7 to 11 per cent of 
bitumen. It should preferably be placed upon a cement concrete 
foundation to a compacted depth of 2 inches. No seal coat will 
ordinarily be required, and maintenance should consist only in 
patching with bituminous concrete until it is necessary to replace 
the entire wearing course. 
SPECIFICATION RBC-—4. 
Broken Stone, Sand, and Filler for Binder Course and Sheet Asphalt 
Wearing Course. 
BROKEN STONE FOR BINDER COURSE. 
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, and when tested all of the broken stone shall ) 
pass a i-inch laboratory screen. 
The stone shall meet the following requirement: 
MoucHneESS; NOG LESS) tha Mes =e. ska ES Sie ys ee Be 
Physical 
Properties. 
SAND FOR BINDER COURSE. 
The sand shall be composed of sound durable stone particles, free from General. 
a coating of clay and loam, which when tested shall all pass a j.inch 
laboratory screen. 
TOTAL MINERAL AGGREGATE FOR BINDER COURSE. 
The total mineral aggregate shall consist of a uniform mixture of the General. 
broken stone and sand, the required grading of each being such as to pro- 
duce, when properly proportioned, a mixture conforming to the following 
limitations for grading. The exact proportion of each constituent pro- 
ducing a mineral aggregate within these limitations shall be as directed 
by the engineer. 
When tested by means of laboratory screens and sieves the total min- Grading. 
eral aggregate shali meet the following requirements: 
Per cent. 
Passing 1-inch and retained on 4-inch screen_______________ 15 to 65 
Passing $-inch Screen and retained on 10-mesh sieve_________ 20 to 50 
IPASSINgeehO-mMeSheISLOV eas sa ae ee ee ee 15 to 35 
