24 BULLETIN 373, U. S. DEPAETMEISTT OF AGEICULTUKE, 



subgracle, 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 + .157 A + .040 B. 



The cost as estimated from this formula should usually be increased 

 by about 10 per cent to allow for wear on tools and machinery 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 thiclaiess 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 ver}^ 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 brick 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 iri'egularly 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. ^Vhere the foundation is con- 

 structed 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 for a considerable period. The 

 shoulders and drainage structures, of course, need occasional atten- 

 tion, 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 condi- 

 tions 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. Such measurements as have been made 



