NEW YORK, MAY 18, 1907. 
WEEKLY, fl.00 PER YEAR. 
Vol. LXVI. No. 2990. 
A SILO OF CONCRETE BLOCKS. 
What the Experts Say of It. 
What would he your opinion regarding the value of a 
silo made of hollow concrete blocks? These blocks are 
being used for building houses, as you know, and are well 
thought of by many, but would they be suitable for silo 
building? In the average silo, what is the pressure, that 
is, how many pounds per square foot are figured? 
Make the Blocks Right. 
I have had no experience with the use of hollow con¬ 
crete blocks for the building of silos, though I see no 
good reason why they should not be used, especially if 
in the making of the blocks a sufficient amount of 
cement is used in them, and if the blocks are allowed 
to stand for three or four months, at least, before using 
them, in order that the mixture may thoroughly set or 
harden. I know that blocks that contain too large a 
proportion of sand, and which have not been allowed to 
stand long enough before using in the building, will not 
resist rain, and presumably will not be airtight. Nat¬ 
urally, if such is the case, they would not be satisfac¬ 
tory for a silo. e. b. voorhees. 
New Jersey. 
Permanent as the Eternal Hills. 
Concrete blocks, hollow, make an excellent silo. 
Those in use have given satisfaction except where the 
silo has not been strengthened by iron rods. It is very 
easy to arrange a form wherein the blocks are molded 
in such a way as to make a continuous hollow about 
the silo, in which can be embedded an iron rod. Block 
silos without this support have sometimes burst at 
the bottom owing to the heavy pressure of the silage, 
which amounts to 330 pounds per square foot at a depth 
of 30 feet. The expansion of the rod and the cement 
is practically identical, and consequently we get no 
cracking of the silo where the support is thus embedded 
in the blocks. There are a good many cement silos in 
Michigan which are doing excellent service. Some of 
them are built of solid concrete. We have one at the 
college which will stand until the day of judgment, as 
permanent as the eternal hills, because it is one solid 
stone. Others are built hollow, as indeed they should 
be, and some of them of blocks. L. R. 
Hunter, South Lyons, Mich., has built one 
by erecting 2x4’s at a distance of 16 inches 
from center to center, standing the 2x4’s m 
a circle and putting in elm lath on the in¬ 
side and outside, and plastering inside and 
outside with cement. He has made this 
plastering about two inches thick inside and 
out. Whereas the walls have cracked in 
years subsequent to the building, white¬ 
washing with Portland cement about the 
consistency of cream has closed the cracks 
and kept the silage. When this silo has 
stood a little longer it ought to be a model 
to some men who want a cheap and effective 
s il°- c. D. SMITH. 
Michigan. 
The Pressure in a Silo. 
I here is no doubt regarding the suit¬ 
ability of hollow concrete blocks for silo con¬ 
struction, provided, of course, the blocks 
have been properly made of good materials 
properly put together and sufficiently sea¬ 
soned before they are put under strain from 
the pressure of the silage. The pressure of 
silage on the walls of a silo increases with 
the depth of the silage and at a rate of 
approximately 11 pounds per square foot for each foot 
of depth. At a depth of 10 feet the pressure at the 
time the silage is settling may be as great as 110 pounds 
per square foot, at 20 feet as great as 220 pounds, and 
at 30 feet as great as 330 pounds per square foot. 
A here cement blocks are used in the construction of 
deep silos it is probable that they would need to be 
reinforced at the bottom, especially if the space between 
the doors is narrow. If a continuous door was used it 
would be of course necessary to tie with iron rods at 
frequent intervals all the way up. It is very doubtful 
if cement blocks sufficiently thick for silo construction 
A CONCRETE STOVE. Fig. 190. 
could be made and laid as cheaply as the walls of a 
good stave silo can be completed. Unless the blocks 
manufactured are more than 18 inches long the curva¬ 
ture is of but little importance when the diameter of 
the silo is greater than 15 feet inside. It must be re¬ 
membered that of course the blocks must be laid in 
cement mortar by a mason and plastered on the inside 
with cement mortar to leave the surface smooth, unless 
unusual care is taken in the construction and laying of 
the blocks. All of this, of course, adds to the original 
cost of the blocks in the construction. f. h. king. 
A Success in Ohio. 
The great advance in the prices of lumber suitable for 
the construction of silos has called renewed attention 
to silos built of cement of some form, and more lately 
to cement block pits, a few of which were built two 
years ago and last season as well. In the building of 
concrete walls there seems to be a great amount of the 
heaviest sort of labor, and tremendously strong walls 
needed, owing to the liability of the walls to crack. This 
was overcome by “bedding” either iron rods in the 
cement walls each foot or so, or using strands of heavy 
wire in the same way. This enabled the builders to use 
far less material, and at the same time with the rein¬ 
forcements get even a stronger wall. A neighbor sev¬ 
eral years ago built a silo on a wholly novel plan, and it 
has proved to meet all requirements, and promises to 
last for years to come. The walls are of the common, 
hollow building brick, 9x9, and 18 inches long, with 
the usual center partition. These bricks were set upon 
end in a circle, and the interior spaces filled in with 
cement, with the further precaution of pushing short 
sticks of stove wood down inside, so that each stick 
would be divided between the upper and the brick below 
on which it half rested. The bricks were laid, and 
pointed up in the best of hydraulic cement, and the inte¬ 
riors as well filled “full.” The silo walls became firm 
as if one brick; not a crack ever came in it, or any signs 
of internal pressure. The idea that concrete blocks 
could be used seemed to have originated in several 
places in Ohio about the same time. Two years ago 
Mr. Haserot, of Cleveland, desired to build four large 
silos of about 250 tons each capacity for his different 
canning establishments, and asked my advice about 
building of concrete blocks. The result of the matter 
was that the silos were built of the blocks. A mold 
was fashioned that pressed these blocks into segments 
of a circle. Each block was three feet long, eight inches 
thick and 16 inches wide across the “bed.” Two 
holes were made in each biick, and each brick was chan¬ 
neled on both surfaces to make a better cement “clinch.” 
No rods were used to strengthen the walls. The blocks 
were liberally bedded in the best of Iroquois cement, 
and when this set the walls actually became one piece 
of cement. There are several new patented systems of 
reinforced cement now coming into use for house¬ 
building, which may in time be adapted to silos. Some 
are formed in blocks, while in others the con¬ 
crete is applied upon a sort of metal 
skeleton. 
In building the blocks it needs a capable 
man to supervise. The cleanest and sharp¬ 
est of sand, free from dirt, must be used, 
with the best of cement. This needs to be 
most thoroughly mixed, and then made as 
wet as can be well molded, and the cement 
pressed into the molds with real hard tamp¬ 
ing. The blocks should be dried in the 
shade, and sprinkled down every day for 
quite a while, and the block should become 
well seasoned before laying into the wall. 
The proportions must be left to the judg¬ 
ment of the maker, but three of sand to 
one of cement will be not far out of the 
way. I would want to know exactly what 
kind of sand, gravel and cement was used, 
how mixed and “squeezed,” as well as 
cured, if I was to buy building blocks. 
Some blocks, badly made with too much 
gravel in the “mix” and not cured out thor¬ 
oughly, made much trouble and a weakened 
spot in a cement silo that we have in mind. 
In a well-made block silo there is no need 
of any other aid in holding the walls than 
the blocks themselves. The pressure on a 
15-foot silo would never spring or crack the 
walls if on a solid foundation. We know of a great ce¬ 
ment block silo 25 feet in diameter, that is filled to its 
top, and wetted down to make the contents settle, that 
has been so filled , three times without a sign of other 
than perfect security. The lateral pressure of a 30-foot 
silo at the bottom is supposed to be 300 pounds per 
A HOUSE BUILT ENTIRELY OF CONCRETE. Fig. 191. 
