Concrete Silos 155 



a hollow block of two types, the two parts in the 

 block being connected either by a web of concrete 

 or by steel spacers. The blocks are made 8 inches 

 high, 9 inches thick and 24 inches long, with 2 1 /2-inch 

 air space. The blocks interlock in both directions and 

 have a groove on top for reinforcement. 



Perfect Reinforced Block. This system is the prod- 

 uct of the Perfect Reinforced Cement Silo and Cis- 

 tern Company, Delaware, Ohio. The Perfect Silo is 

 built with blocks 2 feet long, 1 foot high and 4 inches 

 thick. 



Each block is reinforced with two iron rods run- 

 ning lengthwise of the block, 6 inches apart. Each 

 rod is looped or turned 6 inches from the end. These 

 loops in the rods coincide with the holes that are 

 formed edgewise through the block, 1 inch in diame- 

 ter and 6 inches from either end. In laying the blocks 

 these 1-inch openings are filled with cement grout and 

 the rod or dowel pin is pressed through the soft 

 cement, connecting the two blocks. Each pin is in- 

 serted in such a way that it passes entirely through 

 one block and half way through the block above and 

 the one below. By this arrangement of loops and 

 dowel pins, inserted in the holes through the blocks, 

 and the use of half blocks, joints are broken in the 

 same way as when an ordinary brick wall is laid. This 

 provides for a continuous lateral reinforcement around 

 the silo every 6 inches, and the dowel pins that run 

 through the blocks from the bottom to the top of the 



