EXAMINATION OF BITUMINOUS ROAD MATERIALS. 



39 



top sieve, after which the cover is put on and the stack .agitated for 

 about five minutes with both rocking and circular shaking. Each sieve 

 is removed in order, and shaken and tapped on a clean piece of paper 

 until no appreciable amount of material comes through. All lumps 

 are broken up by crashing them against the side of the sieve with the 

 ringer or a small spatula. The contents of the sieve are emptied into 

 the pan of the balance. All particles caught in the mesh are removed 

 by brushing across the underside of the sieve and are added to the 

 contents of the pan. As great opportunity exists for wide variations 

 in the results of sand gradings made by different persons, owing to 

 the possibility of always getting a little more material to pass by 

 continued shaking, it is well for the novice to repeat his sifting on 

 any given mesh, after having weighed it, in order to see what fur- 

 ther loss he can produce. If his judgment has not erred, several 

 minutes' further sifting should not produce a loss of over 0.5 gram. 



Where coarse aggregates have considerable material passing a 10- 

 mesh sieve and it is desired to grade this material further, it should 

 be weighed and well mixed, quartered, if necessary, and a 100-gram 

 sample should be passed through the sand sieves. From the per- 

 centages so obtained and the weight of material passing the 10-mesh 

 e, the percentages of the total aggregate which these finer mate- 

 rials represent may be calculated. 



The Office of Public Roads and Rural Engineering has adopted the 

 following recommendations of the Committee on Standard Tests for 

 Road Materials of the American Society for Testing Materials as to 

 the size of wire for standard sand sieves: 



Diameter 



. of wire, 



Mealies per linear men: inches. 



10 0.027 



0165 



..... 01375 



•10 01025 



Diameter 

 , , , .. . . of wire, 



Meslies per linear men: inches. 



50 0.009 



80 .'00575 



100 .0045 



200 00235 



DETERMINATION OF VOIDS IN THE MINERAL AGGREGATE. 



EQUIPMENT. 



J 1,000-cubic-centimeter graduated glass cj Under. 

 ! 500-cubic-centimeter graduated glass cylinder. 

 2 pi<:' • : (i-inch. bore and 2 inches Jong). 



1 w'K)(l<:ii I- ited with soft rubber pad. 



1 iron support with condenser clamp, 

 rubber tubing. 



1 pinchco* 



<|j itiff flat brush, 

 op. 



2 sheets oi manila paper. 



