142 Concrete Silos 



as for a monolithic silo. In starting the walls, however, 

 some readjustment of the radius may be necessary in 

 order to accommodate the construction to the size of 

 units available. The length of silo blocks is not usu- 

 ally changed for the various diameters, so that in order 

 to make it possible to use only whole and half blocks, 

 or such fractions as the machine will make, and thus 

 avoid cutting, it will be well to lay out a test circle 

 after the footings are in and see how closely the blocks 

 conform to the desired size. The circle can then be 

 made slightly larger or smaller to accommodate them. 



The cement mortar should consist of 1 sack of 

 Portland cement to 2 cubic feet of clean sand, with 

 the possible addition of a small quantity of hydrated 

 lime (not over ten per cent), to make it easier to work. 

 Before laying up the blocks, see that they are thor- 

 oughly soaked which will prevent them from draw- 

 ing moisture from the mortar. No more mortar should 

 be mixed at one time than can be used up within 30 

 minutes after first moistening. 



Most blocks now made for silo work have some 

 provision for continuous reinforcement; but if such 

 provision is not made, reinforcing wire must be used 

 between the courses of blocks. A table herewith gives 

 the -amounts of reinforcing necessary for block silos. 



The doors in a block silo are installed similarly to 

 those in silos of other types. For intermittent doors, 

 frames 6 inches wide of 2-inch lumber are placed at 

 proper intervals in the 8-inch wall. This leaves a 2- 

 inch recess on the inner surface of the wall in which 

 will set the wooden door. Vertical steel rods are set 

 in mortar in airtight spaces of the block next each side 

 of the doors, and the horizontal reinforcing hooked 

 around them. Sufficient extra rods are placed across 



