CONCRETE CONSTRUCTION. 



235 



without delay. The total amount of concrete obtained is 

 only slightly greater in volume than that of the gravel or 

 crushed stone used. The following table shows approxi- 

 mately, for four standard formulae, the number of bar- 

 rels of each material required to make one cubic yard 

 (7.1 barrels) of concrete. 



Barrels Barrels Barrels Cubic yards 



FORMS FOR MAKING CONCRETE Hoc TROUGHS. 



863. How many sacks of cement will be required to 

 make 3.5 cubic yards of 1-2^2-5 concrete? How much 

 sand? Gravel or crushed stone? 



Process : The table gives 1.3 barrels per cubic yard. 

 4X1-3 = 5.2 sacks per cubic yard. 

 3.5 X 5.2 = 18.2 sacks cement. Ans. 



864. What amount of materials would be required in 

 the last problem if the 1-3-6 formulae were used? The 

 1-4-8? 



865. What would be the cost, exclusive of labor, of 

 the concrete in problem 863 with cement at $1.80 per bar- 



