VITRIFIED BRICK PAVEMENTS FOR COUNTRY ROADS. 



11 



the curb sections are ordinarily shorter, the bedding must be made 

 correspondingly more secure in order to prevent displacement. 



THE FOUNDATION OR BASE. 



A firm, unyielding foundation is one of the most essential features 

 of a brick pavement. This fact can be more readily appreciated 

 when it is considered that the surface of a brick pavement is made up 

 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 or base depends largely on the mate- 

 rial composing the subgrade and the character of traffic for which the 



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Fig. 2. — Concrete curb and gutter combined. 



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 base may be constructed of broken 

 stone. Where the traffic is comparatively heavy or where the 

 material composing the subgrade is at all unstable, a monolithic 

 concrete base should be used. Bases consisting of a course of brick 

 laid flat upon a previously compacted layer of gravel or broken stone 

 have sometimes been used, and pavements constructed upon bases of 

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

 eral proved satisfactory. At the present time, however, such bases 

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

 bases, and they will therefore be given no further consideration here. 

 Broken-stone bases should be from 6 to 8 inches thick after com- 

 pacting and should be constructed in two or more courses just as in 



