﻿VITRIFIED BRICK AS MATERIAL FOR COUNTRY ROADS. 23 



by the engineer, and the materials composing it shall conform to the 

 following requirements: 



Cement. — The cement shall be of some standard brand, and shaJ.l 

 conform to the United States Government specifications for Portland 

 cement, as contained in Circular 33 of the Bureau of Standards. 

 Cement shall be delivered in sacks of 94 pounds net weight, and each 

 sack shall be considered as having a volume of 1 cubic foot. All 

 sacks which contain lumps or the contents of which have been dam- 

 aged by exposure to the weather or other cause shall be rejected. 



Sand. — The sand shall consist of dry clean quartz grains, and shall 

 not contain more than 5 per cent of clay, loam, or other foreign mate- 

 rials. The grains shall be well graded and of such size that all will 

 pass a |-inch mesh screen and not more than 20 per cent will pass a 

 No. 50 sieve. 



Coarse aggregate. — The coarse aggregate may consist of either 

 broken stone or gravel. Stone shall be hard and tough, and shall be 

 broken in such manner that all will be retained on a |-inch mesh 

 screen and will pass a 1^-inch mesh screen. Not more- than. 75 per 

 cent of the stone shall pass a f-inch mesh screen, and not more than 

 75 per cent shall be retained on such a screen. 



Gravel shall consist of hard, sound particles of stone, thoroughly 

 clean, and shall conform in size to the above specifications for broken 

 stone. 



Placing. — The concrete shall be deposited in place immediately 

 after it is mixed and shall be thoroughly compacted as fast as it is 

 placed. The top surface shall be smoothed by troweling with spades 

 or by some other means approved by the engineer, and when com- 

 pleted shall conform to the proposed surface of the finished pavement 

 at the required depth below it. 



Time of setting. — The concrete shall be carefully protected from 

 the weather and all other disturbing influences, and kept moist by 

 sprinkling for at least 36 hours after it is placed in the foundation. 

 This period may be increased at the discretion of the engineer. Any 

 damage resulting to the foundation before the wearing surface has 

 been laid, no matter what the cause of such damage may be, shall be 

 repaired by the contractor at his own expense. 



Sand cushion. — After the foundation has been constructed and 

 permitted to set as above provided, a layer of sand shall be uniformly 

 spread over the foundation to such depth that when " struck off" 

 and compacted its thickness shall be 2 inches. The sand composing 

 this layer shall be dry when spread and shall conform in all respects 

 to the requirements given above for the sand to be used in concrete. 

 The cushion shall be struck off with a suitable template which con- 

 forms to the cross section of the finished pavement, and shall be 

 thoroughly compacted by rolling with a hand roller weighing not less 



