﻿VITRIFIED BRICK AS MATERIAL FOR COUNTRY ROADS. 



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of small individual blocks, any one of which might be easily forced 

 down, causing unevenness in the surface, if the foundation were poor; 

 and since the ability of the pavement to resist wear depends very 

 largely on the smoothness of the surface, every reasonable precaution 

 should be taken to prevent any unevenness from developing. 



The proper type of foundation depends largely on the material com- 

 posing the subgrade and the character of traffic for which the road is 

 designed . Where the traffic is comparatively light and the subgrade 

 is composed of some firm material which does not readily absorb 

 water, a very satisfactory foundation may be constructed of broken 

 stone or gravel filled with sand. Where the traffic is comparatively 

 heavy, however, or where the material composing the subgrade is 

 defective in any way, a monolithic concrete foundation should be 

 used. Foundations consisting of a course of brick laid flat upon a 



Fig. 2.— Concrete curb and gutter combined. 



previously compacted layer of gravel or broken stone have also been 

 extensively used, and pavements constructed upon foundations of 

 this kind, ordinarily called "double-layer" pavements, have hi gen- 

 eral proved satisfactory, even where the subgrade was composed of 

 an inferior material. At the present time, however, such foundations 

 can rarely be constructed at less cost than the more durable concrete 

 foundations, and they will therefore be given no further consideration 

 here. 



Gravel and broken-stone foundations may be spread hi one or more 

 courses, each of which should be from 5 to 9 inches thick before com- 

 pacting. The materials used should conform in the matter of 

 physical characteristics to the ordinary requirements for similar 

 materials used in constructing macadam roads; that is, the stone or 

 gravel should be clean, hard, tough, and durable, and should be 

 graded in size between certain reasonable, fixed limits. It should be 



