ROAD CONSTRUCTION 



99 



All broken stone must be screened, and any broken stone which will 

 not pass through a 2^ inch ring, or is more than 2^ inches in its 

 largest diameter, must be rebroken or rejected. 



In every case the screenings used on the surface as a binder course 

 must be of the same kind of stone as the top course of the road. 



Rolling. When possible roll the sub-grade with a steam roller. 



If the sub- grade is too sandy to roll, cover with coarse gravel laid on 

 to a depth of 3 inches, or as much more as may be needed to give a 

 good foundation. 



Fill any depressions with the same material until the surface is true and 

 even. 



All broken stone must be rolled in screened layers. 



After spreading the first course of broken stone, begin rolling at the 

 sides, and continue this by running ahead so as to allow from 2 to 5 

 inches of the driving wheel to pass over the shoulder, and backward with 

 the outer edge of the driving wheel from 5 to 10 inches inside the edge of 

 the broken stone. Roll until the stone ceases to 'wave' in front of the 

 wheels, and until it seems firm under foot as you walk over it. Next 

 begin on the other side and roll in the same manner. Then work toward 

 the center until the stone is rolled. Roll each layer of stone in the same 

 manner. 



If the road shows a wavy motion after passing the roller over it three, 

 four or more times, it may indicate too much moisture in the sub-grade. 

 If, on examination, you find this to be true, stop rolling and move ahead, 

 allowing time for the sub-grade to dry out. 



With some coarse, hard granitic rocks it has been noted that after the 

 roller passes over them a few times they begin to ' crawl' and the sharp 

 edges break off. A slight sprinkling of sand or stone screenings, or water, 

 may prevent this. Try one after another of these means, until the work 

 progresses to your satisfaction. You must not expect to prevent the 

 stone from shaking as you walk over it, but you need to continue the 

 rolling until the fragments of stone adjacent to where the foot presses do 

 not move as you walk. Most of the rolling must be done before you 

 spread the screenings. After spreading the screenings, water and roll 

 until the mud flushes to the surface. You can not expect to prevent the 

 stone from kicking out if the teams pass over the road. Keep watch, and 

 in a few days have the roller pass once or twice over the road, after 

 watering, until the loose stones are pressed down out of sight. 



Before spreading any broken stone, great care must be taken to have 

 the sub-grade carefully shaped and thoroughly compacted. 



All shoulders must be shaped and left sufficiently high to roll to the 

 proper grade, before anv broken stone is spread on the road. 



In case of heavy fills you must not run the roller to the edge of the 

 shoulders unless the fill has had time to settle. Work out slowly on this 

 kind of work. 



In every case the screenings used on the surface as a binder course 

 must be of the same material as the top course of the road. 



Excepting where it may lie needed to compact hard, granitic rocks, as 

 before referred to, you will use water only on the top, or binder course. 



You will wet this binder course thoroughly before rolling, but not to 

 the extent of saturating the foundation. You will get better results and 



