SPECIFICATIONS FOR NONBITUMINOUS ROAD MATERIALS, 
In maintaining roads of this type, material as nearly the same 
as that composing the road surface should be used. In patching, 
care should be taken that the finished surface after consolidation 
is smooth and continuous. 
SPECIFICATION GBC-2. 
Gravel, Sand, and Filler for Coarse Aggregate Bituminous Concrete 
Wearing Course. 
GRAVEL. 
The gravel shall be composed of sound, hard, durable fragments of 
rock of high resistance to abrasion and shall contain no particles of 
shale, slate, coal, or other materials which easily disintegrate. It shall 
be free from vegetable or other deleterious matter, and shall contain no 
soft, thin, or elongated pieces. 
The pea gravel, when tested by means of laboratory screens, shall Pea Gravel. 
meet the following requirements : 
Per cent, 
Rassing, s-inchysereen, not less thames 2s a ee eee 95 
Retained on 23-inch screen, not less than--_______-_~_____--___-- 85 
The coarse aggregate, when tested by means of laboratory screens, 
shall meet the following requirements: 
Per cent. 
iRassins, i-ineh= screen. not less) than=="— = 2a ee eee 95 
Totalepassines-inch” Screens. a ee ee PAT) VO) 9-5) 
Retained on i-inch screen, not less than -____________-_____ 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 and sieves, the sand shall 
meet the following requirements: 
Per cent. 
IR ASSN Geri CHS CLOG Teese see aes eee ee ee ee 100 
otal passine 4O-Mesh “Sievers ee a 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. 
Ra SSin gars Og CS CSIC V.C a es eee ee a Ss 100 
Total passing 200 mesh sieve, not less than-____-__~_______-___- 65 
Tests of the grading of the gravel, sand, and filler shall be made in 
accordance with the following methods: 
Grading of Gravel, U. S. Department of Agriculture Bulletin 555, p. 32. 
Grading of Sand and Mineral Filler, U. S. Department of Agriculture 
-——-— 
Bulletin 555, p. 33. 
This specification is intended to cover the mineral constituents 
of a roughly proportioned bituminous concrete consisting of from 
45 to 60 per cent gravel or coarse aggregate, from 30 to 45 per 
cent sand or fine aggregate, from 3 to 5 per cent mineral filler, and 
from 5 to 8 per cent bitumen. This mixture should preferably be 
58683 °—18—Bull. 704-3 
General. 
Coarse 
Aggregate. 
General. 
Grading. 
General. 
Fineness. 
Methods of 
Testing. 
| 
