CHAPTER XXV 



SAND-CLAY AND GRAVEL ROADS 



Clay Roads. By careful construction and continued care 

 an earth road may be made fairly satisfactory. This is true 

 where such a road is made of clay. The construction and 

 maintenance of a clay road consist primarily in providing; 

 drainage. Such a road should be kept as dry as possible. 

 It should have sufficient slope from the center toward the 

 sides to insure quick surface drainage to the side ditches; 

 and, as far as practical, underdrainage should be provided to 

 carry off the water that comes up from below. At best, how- 

 ever, the clay road is not highly satisfactory. During the 

 wet weather it becomes soft, and owing to the stickiness of 

 the clay the surface is rapidly destroyed. 



Sand Roads. In many localities the surface of the roads 

 is composed largely of sand. Sand roads present an entirely 

 different problem from clay roads; they are at their worst 

 when dry, and are best when moist. For this reason some 

 skilled highway engineers advise that sand roads be made 

 flat, or without a crown. Straw, sawdust, and other mate- 

 rials are added to the sand in order to hold the moisture, 

 causing the sand to remain as compact as possible. It is 

 also noticed that sand roads are best when shaded by trees. 



Sand-Clay Roads. Where clay roads and sand roads 

 exist in the same locality, it has been observed that nearly 

 always there is a good piece of road between the stretch of 

 clay road and the stretch of sand road. This would indicate 

 that a mixture of sand and clay makes a better road surface 



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