16 BULLETIN ‘04, U. S. DEPARTMENT OF AGRICULTURE. 
SPECIFICATION GW-1. 
Gravel for Water-bound Gravel Roads. 
General. The gravel shall be composed of fragments of hard, durable rock, of 
high resistance to abrasion, together with sand and clay or other binding 
material, and shall be free from thin or elongated pieces. 
Per cent. 
Quality. Cementing value of material under 14-inch mesh shall be not 
MESS Cine rt ee ee ae ne ecg eg Se a 50 
1. For base course: 
(a) The gravel, when tested by means of laboratory screens, 
shall meet the following requirements: 
Passing a 3-inch screen, not less than ___________ 95 
Lotal retained vone:-inchys Cheenm as eens sane eee ance 50° to: 75 
(6) The material retained on the 4-inch screen is known as 
coarse aggregate. The coarse aggregate, when tested 
by means of a laboratory Screen, shall meet the fol- 
lowing requirement: 
Total retained on 13-inch screen_______________.. PAD: {HOY TAD 
(c) The material passing the 43-inch screen is known as fine 
aggregate. The fine aggregate, when tested by means 
of a laboratory sieve, shall meet the following re- 
quirement: : 
Total passing, 200=mesh ‘Sievel 222 2 eee es 15 to 35 
2. For wearing course: 
(a) The gravel, when tested by means of laboratory screens, 
shall meet the following requirements: 
Passing a 2-inch screen, not less than____________ 95 
Totaly retained: on 4-mcChysereen= seen ss eee ee BORO ae 
(6) The material retained on the i-inch screen is known as 
coarse aggregate. The coarse aggregate, when tested 
by means of a laboratory screen, Shall meet the fol- 
lowing requirement : 
Total retained-on d-inch screen! 2222 Se PAR GIG) Ti 
(c) The material passing the 34-inch screen is known as fine 
aggregate. The fine aggregate, when tested by means 
of a laboratory sieve, shall meet the following require- 
On 
ment: 
wiotal passing, 200-meshtsieve == eee eee 15 to 35 
Method of Tests of the quality and grading of the gravel shall be made in accord- 
Testing. ance with the folowing methods: 
Cementing value, U. S. Department of Agriculture Bulletin 345, p. 19. 
Grading, U. S. Department of Agriculture Bulletin 555, p. 82 (9). 
This specification covers the quality and grading of a sand- 
clay-gravel suitable for use in the construction of a water-bound 
gravel road. It applies to gravels composed mainly of fragments 
of quartz or other nonbinding rock types. In cases where the 
gravel is composed essentially of limestone or other materials 
which will bond under traffic, considerably less material under 
200-mesh may be allowed. The sizes specified contemplate a base 
course of at least 4 inches, and a wearing course of at least 3 
inches in thickness after consolidation. The relative proportions 
of the various intermediate sizes have been drawn so as to exclude 
only gravels of manifestly poor grading. In cases where the 
gravel, although otherwise acceptable, is deficient in sand or 
clay, such materials, if available, and of a suitable character, 
may be added in sufficient quantities to bring the grading and 
cementing value of the gravel to within the limits specified. This 
should be done by spreading the sand or clay uniformly over the 
loose gravel surface and thoroughly harrowing with a spike-tooth 
harrow, after which the surface is consolidated. 
a 
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