VITRIFIED BRICK PAVEMENTS FOR COUNTRY ROADS. 9 



down in layers not over 8 inches thick, and each layer should be 

 thoroughly rolled. In excavation care should be exercised, if the 

 material is earth, not to permit plows or scrapers to penetrate below 

 the subgrade. The subgrade in both excavation and embankment 

 should be brought to its final shape by means of fine grading with 

 picks and shovels and rolling. 



When completed the subgrade should be uniform in grade and 

 cross section, otherwise the foundation must be made unnecessarily 

 thick where depressions occur, in order that its grade and cross 

 section may be uniform and its thickness not less at any point than 

 that required. The subgrade should be repeatedly rolled and re- 

 shaped until the desired shape is secured. If curbs are constructed 

 independent of the base they should be set before the final finishing, 

 in order that they may be made to serve as a guide for this work. 



The shoulders should never be less than 4 feet wide and should 

 consist of some material which compacts readily under the roller and 

 does not readily absorb water. Not infrequently one of the shoulders 

 is made sufficiently wide to form an earth roadway parallel to the 

 brick pavement. Such an arrangement serves to relieve the pave- 

 ment of considerable traffic during favorable seasons and also affords 

 some advantage to horse-drawn traffic. The general method of con- 

 structing shoulders for brick roads is not essentially different from 

 that employed for other types of pavements. 



CURBING. 



All brick pavements should be supplied with strong, durable 

 curbing, both on the sides and at the ends. Otherwise the marginal 

 brick will soon become displaced by the action of traffic, and their 

 displacement will, of course, expose the brick next adjoining, so that 

 deterioration might eventually spread over the entire pavement. 

 Properly constructed curbing, on the other hand, will hold the pave- 

 ment as in a frame and enable the brick to present their combined 

 resistance to the destructive influences of traffic. 



Satisfactory curbs may be constructed of stone, Portland cement 

 concrete, or vitrified clay shapes made especially for this purpose. 

 Wood has also been used for curbs to a limited extent, but when it is 

 considered that the life of a brick pavement under ordinary condi- 

 tions should far exceed the life of any wood curb which might be 

 devised, the economy of employing a more durable material is 

 readily apparent. 



Stone curbing may be made from any hard, tough stone which is 

 sufficiently homogeneous and free from seams to admit being quar- 

 ried into blocks not less than 4 feet long, 5 inches thick, and 18 

 inches deep. On account of their ordinarily homogeneous structure, 



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