﻿VITRIFIED BRICK AS MATERIAL FOR COUNTRY ROADS. 17 



The first application should proceed about 50 feet in advance of the 

 second. Usually both applications are made by the same crew of 

 laborers. They simply turn back after having covered the allowable 

 distance with the first application and, mixing the grout in the same 

 boxes, bring up the second application. The second application of 

 grout should completely fill the joints flush with the top of the brick. 



After the joints are filled as described above and the grout has taken 

 its initial set, the entire surface should be covered to a depth of 

 approximately one-half inch with clean sand. This is done to protect 

 the pavement from the weather and to keep it in a moist condition 

 while the grout is hardening. If necessary, in order to keep the sand 

 moist, it should be occasionally sprinkled for several days after it is 

 spread. 



The sand covering should be permitted to remain on the surface 

 for at least 10 days, and during this period the pavement should be 

 kept entirely closed to traffic. If the weather is unfavorable, the 

 length of time during which traffic is kept off the road should be 

 increased. 



EXPANSION CUSHIONS. 



It has been customary in the past to provide both longitudinal and 

 transverse bituminous expansion cushions in grout-filled brick pave- 

 ments, but recent practice has demonstrated that the transverse 

 cushions may be advantageously omitted if proper longitudinal 

 cushions are provided. The principal objection to the use of trans- 

 verse expansion cushions is based on the fact that the material com- 

 posing the cushions frequently softens during warm weather and 

 runs out toward the curb, thus leaving the edges of the adjoining 

 brick exposed to destructive impact from the wheels of passing- 

 vehicles. Even if the cushion consisted of a material which does not 

 run in warm weather, it is necessarily softer than the brick, and the 

 natural result is still the development of unevenness in its immediate 

 vicinity. No such objection can exist concerning longitudinal 

 expansion cushions, however, if they are placed adjacent to the curbs 

 and constructed of proper material. They not only furnish a means 

 for the pavement to expand and contract with changes in tempera- 

 ture but they also eliminate to a large extent the disagreeable 

 rumbling which has been so frequently associated with grout-filled 

 brick pavements. 



The bituminous material of which the expansion cushions are made 

 should be such as to remain firm in summer and not to become brittle 

 in winter. It should also possess the quality of durability. In order 

 to insure that any given material is suited for such a purpose, it is 

 usually considered necessary to prescribe certain laboratory require- 

 ments to which it must conform, and examples of these, which have 

 7709°— 13 3 



