SPECIFICATIONS FOR NONBITUMINOUS ROAD 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 
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 : 
Hrenehecoeiiereni: Ol wed lwMObeleSS atin ayn wee meee ie Bae ge ae eee 8 
FEGUEHR ESS NOE LESS yo bE Ties ee aes Ne a pa Se ae 8 
That portion of the product of the crusher, which, when tested by 
means of laboratory screens, will meet the following requirements: 
Per cent. 
Passing y.-INCh SCreen. MOlMeSS: Chan a2 2 oe ee eee a 95 
Retamedzon inch Screens NOt TESS] th ats sale sme es Ree ee ee 85 
That portion of the product of the crusher, which, when tested by means 
of laboratory screens, will meet the following requirements: 
Per cent. 
Passined-inechisscreens not less) (hana = Sas Sees see 95 
ERO EAE ASS UI Sees o 0) CHES CIC CTD at na ereg eee a si bee ee Cee RE Ee OE al 25 to 75 
Retainedion: 4-inchi screen) not Tess than] —= = see eee 85 
SAND. 
The sand for fine aggregate shall be composed of sound, durable stone 
particles, free from a coating of clay or loam. 
When tested by means of laboratory screens the sand shall meet the 
following requirements : 
Per cent. 
JE FANS Sir aifepe aa Ol ORCAS oe ee a 100 
Ro tala S Sin Pye 2M ESET yee ees eee se ey Se eee 30 to 70 
Retained on 200-mesh sieve, not less than -____________ 90 
MINERAL FILLER. 
The mineral filler shall consist of limestone dust, dolomite dust, Port- 
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 
the following requirements: 
Per cent. 
IPA SSim 225 OSM CSW SI CV Cons eee sea sl oe en Oe a De 100 
Total passing 200-mesh sieve, not less than________________-___-_ 65 
Tests of the physical properties of the rock and of the size or mechan- 
ical analysis of broken stone, sand, and mineral filler shall be made in 
accordance with the following methods: 
. French coefficient of wear, U. S. Department of Agriculture Bulletin 
344-220. 6. 
. Toughness, U. S Department of Agriculture Bulletin 347, p. 15. 
Size of broken stone, U. S. Department of Agriculture Bulletin 555, 
Degen 2c 
Mechanical analysis of sand and mineral filler, U. S. Department of 
~=—=— 
Agriculture Bulletin 555, p. 33. 
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This specification is intended to cover the mineral constituents of 
a roughly proportioned bituminous concrete consisting of from 45 
to 60 per cent broken 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 
General. 
Physical 
Properties. 
Chips. 
Coarse 
Aggregate. 
General. 
Grading. 
General. 
Fineness. 
Methods of © 
Testing. 
