CONCRETE CONSTRUCTION. 



233 



and entrance way, if the side walls are 8 inches thick and 

 the floor 4 inches thick? 



860. About how much concrete will be required to 

 construct a semi-cylindrical roof 3 inches thick, the two 

 ends, and an entrance way, for the root cellar in the last 

 problem ? 



861. How much concrete was required for the two 

 circular silos, 20 feet diameter, 32 feet high, 12-inch walls, 

 and 8-inch floors, now in use at the U. S. Soldiers' Home, 

 Washington, D. C.? 



CONCRETE FENCE POSTS. 



At the bottom is shown the face of the post. At the top at the left the form 

 for making, and at the top at the right is shown enlarged section of post. 



862. How much concrete is required to make ten V- 

 shaped and ten round-bottom hog troughs, length 6 feet, 

 with cross sections as shown in the cuts on page 235 ? 



Concrete formula. A formula is used to indicate the 

 relative amounts by volume of each of the three ingredi- 

 ents. A 1-2-4 concrete is one composed of one part of 

 cement, two parts of sand, and four parts of gravel or 



