﻿20 BULLETIN 23, U. S. DEPARTMENT OF AGRICULTURE. 



subgrade, a 6-inch concrete foundation, and suitable curbs, may be 

 estimated by substituting in the formula: 



Cost per square yard = 1.90 L + .213 C + .138 S 4- .157 A + .045 B. 



The cost as estimated from this formula should, however, be 

 increased by about 10 per cent to allow for wear on tools and machin- 

 ery and to guard against unforeseen contingencies. If it is desired 

 to use a different thickness of foundation, it is safe to assume that 

 each inch subtracted or added to the thickness of the foundation 

 will make a corresponding difference of from 8 to 12 cents in the cost 

 per square yard. 



MAINTENANCE OF BRICK PAVEMENTS. 



If brick pavements are properly constructed at the start, the work 

 of maintaining them is very slight. Under the closest inspection, 

 however, some inferior material is likely to become incorporated 

 either in the foundation or in the surface, and it is, therefore, very 

 important that a brick pavement be very carefully watched for the 

 first few years of its life to see that no unevenness develops either 

 because of defective bricks having been used in the surface or because 

 of insufficient support from the foundation at any point. Whenever 

 any unevenness develops, it should be immediately rectified. Other- 

 wise the pavement will become irregularly worn in the vicinity of the 

 defects and expensive repairs will eventually be necessary. 



Not infrequently weak spots develop in broken stone or gravel 

 foundations, owing to surface water finding its way through joints 

 in the pavement which have not been properly filled with grout. 

 Careful observation of the joints should, therefore, constitute a part 

 of the early maintenance work, and any defective joints discovered 

 should be immediately remedied. Where the foundation is con- 

 st! ucted of concrete, however, slight defects in the joints seldom 

 result in any very serious damage. 



If care is exercised to correct all defects which appear within the 

 first few years of the life of a well-constructed brick pavement, the 

 work of maintaining the pavement proper should thereafter, except 

 for cleaning, be almost negligible. The shoulders and drainage 

 structures, of course, need occasional attention, just as in the case of 

 any other pavement, but if they are properly constructed at the start 

 repairs will usually be very slight. 



The life of a well-constructed brick pavement can not be estimated 

 with any great degree of exactness, first, because the traffic con- 

 ditions are constantly changing, and, second, because no brick pave- 

 ment which has been constructed in accordance with the best modern 

 practice has yet worn out. The amounts of wear sustained by given 

 pavements during comparatively long periods of years have been 



