12 BULLETIN 220, 17. S. DEPARTMENT OF AGRICULTURE. 



SAND-CLAY ROADS. 



Plate VI, figure 1, illustrates the construction of a sand-clay road 

 16 feet wide and 8 inches thick when compacted. The crown, as 

 shown, is 1 inch to the foot. 



Section A represents an unimproved sand road about 33 feet wide; 

 section B, the road slightly rounded to receive the clay; section C, 

 the road covered with clay to a depth of 6 inches; section D, the 

 harrowing or mixing process; and section E, the completed road. 

 The process is as follows: 



The road is first shaped, then covered with from 4 to 6 inches of 

 clay and worked with a disk or tooth harrow until the sand and 

 clay are thoroughly mixed, first dry and finally wet. The final 

 mixing should be done, if possible, during rainy weather. When 

 the mixing has been done, the surface is brought to a crown of 1 

 inch to the foot with the road machine or split-log drag and covered 

 with a thin layer of sand. After two or three rams it may be found 

 necessary to apply more sand. This method produces a smooth, 

 cheap, and satisfactory road suitable for light traffic. 



Similar results can be secured by adding sand to a clay road and 

 providing good surface drainage. When building on a clay foun- 

 dation, it is advisable to plow the clay before adding the sand in 

 order to insure a thorough mixing. 



The failure of a sand-clay road is generally due to one of two 

 causes, the use of an unsuitable material or the combination of the 

 sand and clay in wrong proportions. The clay should be of a quality 

 which, while sticky, yet will mix readily with the sand and form a 

 firm bond after the wet mixture has been shaped and dried out. 

 Some clays, such as the "joint" clays, have so little of the plastic 

 or sticky quality that after a rain they quickly separate from the 

 particles of sand ■ and make a dusty road. Where available, the 

 sand selected should be sharp and coarse. With regard to the pro- 

 portions of sand and clay, any excess of clay above the amount 

 necessary to fill the tiny spaces between the grains of sand will 

 result in a more or less muddy road. Farmers' Bulletin 33 1, 1 "Sand- 

 clay and Burnt-clay Roads," gives full information on the subject 

 of constructing these roads. 



GRAVEL ROADS. 



Plate VI, figure 2, illustrates the stages of construction for one 

 type of gravel road. The graded width is 33 feet and the surfaced 

 width is 16 feet. The crown is three-fourths inch per foot. 



Section A represents the side ditches, shoulders, and the prepared 

 subgrade, with the center about 10 inches higher than the bottom of 

 the side ditch. 



1 Qopies of this publication will be sent free to persons applying to the Secretary of Agriculture, Wash- 

 ington, D. C 



