UNIVERSAL PORTLAND CEMENT CO. 
71 
The following estimate of labor required to construct monolithic 
silos is based on experience in a large number of cases, the materials being 
Labor mixed by hand. The labor here given is approximate, and does 
Required not include that required to haul materials: 
Silos 12 feet in diameter 10 to 16 days (4 hours per day) 4 men 
Silos 16 feet in diameter 10 to 16 days (4 hours per day) 4 to 5 men 
Silos 20 feet in diameter 10 to 20 days (4 hours per day) 5 men 
Silos 22 feet in diameter 12 to 20 days (4 hours per day) 5 men 
Steel rods are more commonly used than other kinds of reinforcing 
only because they come in standard sizes, the strength of which is 
„ . , . definitely known. Any other kind of reinforcing, such as Triangle 
mesh, having one section rigidly attached to another, will do 
the work equally well, and may be successfully used if a sufficient quan- 
tity is put in to give a cross-section area equal to that of the rods recom- 
mended on chart on page 72. The quantities and weights of Triangle 
mesh required for varying heights and diameters of silos are given in a 
table appearing on pages 100 and 101 of the appendix. 
For all monolithic silos, where rod reinforcing is used instead of 
Triangle mesh, the vertical reinforcing should be 3^-inch round or twisted 
Spacing of pl^ced in the middle of the wall at intervals of about 3 
Rods feet. _ .... 
Choosing the horizontal remforcing is a different problem. 
Its size and spacing depends upon the diameter and height of the silo. 
The steel rings prevent internal pressure from bursting the walls. This 
pressure is due to the weight of the silage inside. At the top the weight 
of the silage is least and only a small amount of steel is needed. But 
farther down the weight increases and more steel must be used. At the 
bottom the entire weight of silage tends to burst the walls and the steel 
should be heaviest and closest together to take the maximum strain. 
All silos must be reinforced in some manner. The monolithic silo gives 
perfect protection to the reinforcement, from rust and fire. The graphic 
chart on the following page gives the sizes of rods and spacing for all 
common diameters and heights. The figures are liberal enough to give 
perfect safety. 
All horizontal reinforcement must be made into continuous bands 
by splicing. At the splices the rods must be lapped for a distance equal 
to sixty-four times their diameter and tightly wrapped with 
Plcwhi^'the 34-inch rods this lapping would be 16 inches. For 
Rhigs^ ^-inch rods 24 inches and for i^-inch rods 32 inches. Before 
the outer form is set up for the first ring of concrete, the hori- 
zontal reinforcing should be wired to the vertical rods, at least as high 
as the height of the forms. The position of the reinforcing is clearly 
shown in the section on page 63. The first band should be placed 2 inches 
above the foundation. From this point upward the spacing is indicated 
in the chart. For each ring of concrete the steel should be similarly 
placed. If a concrete cornice is built an extra reinforcing band is placed 
around the top to strengthen it. 
The graphic chart on the opposite page can be better understood if 
a specific example is given. Suppose that you wish to build a silo 14 feet 
