CONCRETE 



11 



HF 40 



= 93 = 43 %; which means that 43 per cent of the dry materials 



by weight should be cement plus sand, and 57 per cent stone. 

 About 3 per cent of the stone is overlapped by the sand, but 

 this is so slight it need not be considered here in determining the 



s6D.4-LlSO.J3cJ 



combined curve. Theoretically, no overlapping in this case 

 should occur, but it is practically impossible in a revolving 

 screen to prevent some fine material being carried over to the 

 openings of larger size. The best proportions of the cement, 



