244 



CHEMISTRY OF FARM PRACTICE 



Table XXV gives the quantities of each material required 

 in 1 cubic foot of concrete. With this data it is easy to 

 calculate the amount of material for any given structure. 

 A sack of cement contains 1 cubic foot of cement and four 

 sacks constitute a barrel. 



FIG. 80. Concrete watering trough. (From 



Drafting.") 



Howe's " Agricultural 



Example.* Let us suppose that the work consists of a 

 concrete silo requiring in all 935 cubic feet of concrete, of 

 which 750 cubic feet are to be 1 : 2 : 4 concrete, and 185 

 cubic feet are to be 1 : 2^ : 5 concrete. Enough sand 

 and cement are also needed to " paint " the silo inside 



* From U. S. Dept. of Agr. Bulletin, 461. 



