Silos and Silage in Colorado. 
45 
used the two sacks will fill it but half full. Five half barrels of sand 
and gravel (or 2]/ 2 barrels) would make a one to five mixture, etc. 
Caution .—It must be borne in mind that in all cases the propor¬ 
tion of cement to sand and gravel will depend upon the character of 
the sand and gravel in each particular bank. To use a certain mix¬ 
ture without knowing how much sand is present may result in faulty 
concrete. The proportion of cement must be increased when sand 
is fine. Dirty sand and gravel may be rendered usable by washing 
but not by increasing the proportion of cement. 
It will be understood, therefore, that a mixture of one part of 
cement to five parts of the mixed sand and gravel, ordinarily found 
in the gravel banks in this state, is the widest mixture that is per¬ 
missible when all materials are satisfactory. 
Mixing Platform .—A tight level mixing platform about ten 
feet wide by 14 or 16 feet long should be constructed. A smaller 
platform than this will not be ample for the four men v*ho should 
work at mixing. 
Manner of Working. —The work is accomplished most advan¬ 
tageously when all four men work together in mixing a batch of 
concrete. Two men then remain on the platform. One of them 
fills the buckets, while the other elevates them to a man above. One 
man inside the silo receives the bucket and empties it into the forms. 
The fourth man uses the tamper continuously while the batch is 
being placed in the forms. 
Sizes of Batches.—A batch in which two sacks of cement at a 
time are used is a desirable size. This may be handled nicely upon 
the platform and placed in the forms before it begins to set. 
Manner of Mixing. —The sand and gravel are first placed upon 
the mixing platform and spread out evenly. The two sacks of ce¬ 
ment are then emptied over this and spread evenly. The same 
gravel and cement are then thoroughly mixed together while dry. 
Two men should stand at either end of the pile and shovel it over 
outward. It may then be turned back together. This procedure 
should be repeated once more. No rule will be given for the num¬ 
ber of times this should be turned. The cement should be so thor¬ 
oughly mixed that no streaks will show and the color of the entire 
mass will be uniform throughout. Partial mixing should not be 
done with the idea that it will be made thorough when water is 
added. 
Adding Water .—The dry mixture should be spread out and 
the center hollowed out, thus forming a crater. Water may be 
poured in this crater and the dry mixture from the edge may be 
gradually worked in. Square cornered shovels will be found the 
