Demaree, F. H. (Frank Howard)

University of Missouri: MOspace

UNIVERSITY OF MISSOURI COJ.I~EHE OF AGRICUL'J'UlW Agricultural Experiment Station COLUMBIA, MISSOURI, JULY, 19IT CIRCULAR NO. 49 THE REINFORCED CONCRETE SILO . By F. H. DEMAHEE , Ac tin g A g ronomist. Sil age is comin g into 111 0re g'e neral use eve ry ye;lr and th e co ncre te s il o as a mea ns o f prese rving g' rec n fee d ha s beco me ve ry popu la r. T he popu lari ty of thi s s il o is we ll founded sin ce it is durab le, e ffi cie nt, nre a nd ve rmin proo f, and th e cost is not cxces-Sl\· e. Size of Silo - T he size o f th e s il o IVhi ch is prac tical to build will depe nd upon th e num be r o f animal s to be fe ci a nd th e lengt h First sed io n of so lid co n cre le s il o co mpl eted, show in g fOl'lnR loose ned and ready to be ra ised. of th e fee ding peri od . It is necessa ry to fee d two in ches or more of silage da ily from th e top afte r fe eding has begun in ord er th at it may not spo il. This be ing t ru e, ca reful at tenti o n to size is esse n-tial in o rd e r to save feed aft e r it has once bee n sec ured . The di ame ter of th e sil o shou ld de pend upon th e number of anima ls to be feci whi le the heig'ht will depe nd upon the leng th of th e fee ding !leaso n. The latte r wil l of course vary with th e loca lity. lIS 116 MISSOURI AGRICULTURAL EXPERIMENT STATION, CIRCULAR 49. The following tabl.e will aid in determining the size to build both in diameter and height: TABLE NUMBER I. SHOW1NG SIZE AND CJ\PACITY OF SILO FOR HERDS OF VARIOUS SUI.S. ----_._-- --------------- -FE£D FOR 180 DAYS No . OF Cows CAPACITy-TONS DIAMRTRR HEIGHT -------7- 10 10 feet 25 feet 36 10-12 10 feet 28 feet 4~ 12-'5 I I feet 29 feet 60 '5-20 '2 feet 32 feet 73 20-2 5 13 feet 33 feet 83 25-3 0 '4 feet 34 feet "5 30-35 IS feet 3'" feet IF 35-4° 16 feet 35 feet 15 8 40-45 20 feet 35 feet 25 8 Making the Forms.-After having decided upon the size of silo needed the next thing is to secure forms for the construction of the walls. If the forms of correct size can be hired in the neighborhood or from a distance it will be advisable to secure them rather than to go to the trouble of making them. If not, the cost of making is not excessive. They are fairly simple and can always be hired out or sold for enough to repay the cost of construction. The forms can be most easily made in six sections each. To mark out patterns observe the following: Clean off a large space on a barn floor, then select a long piece of straight stripping at least 20 feet in length. Nail to the floor at any convenient place and from the center of the nail me~sure out on the strip the exact distance of the radius of the silo to be built. Drive a nail through the stripping here so that the point will scratch. If the wall is to be six inches thick measure from the center of this nail six inches farther and drive an-other nail so that it will scratch. Strike a long arc with the two nails. Now take a fine wire, tie a pencil or piece of chalk to one end and measure it the exact length of the inside radius of the silo. Select any point on the inside curve, mark it with chalk, then strike a point on this same curve as far as the string will reach from the point se-lected. (See Fig. I.) This will mark off a part of the circle equal to 1-6 of the circumference of the silo. The enclosed segment of the circle so described may be divided exactly in halfby laying a straight board from the two points designated, measuring exactly half the distance and projecting the line from the center of the circle through the middle point of the board described. From these two points which are marked X in the diagram measure back toward the center four inches inside the first circle and eight inches beyond the outer THE REINFORCED CONCRETE SILO. II7 circle. Now take a plank ten feet by eight inches and one inch thick, saw exactly in the midJle and lay them as indicated in the diagram. Nail lightly to the floor and with the scratching nails, scratch out the curves as shown. This will make one pattern each for the inner and outer forms. Since the patterns are only half large enough for a full section, two of them must be nailed together in order to make the full length. The strips to be used in holding the two parts of the section together should be at least four feet long and cut on the same circle as the form. A glance at the photograph of ,the~ forms will show this. Fig. I-Diagram "huwing method of makillg patte,ns for forms of a con-crde silo 16 feet in diameter. For different sizes changes in measurements may be made in proport.ion. The forms should be at least three feet high so that it will take six pieces from the pattern to build each section of the form. This will mean thirty-six of the inner and thity-six of the outer patterns. When cLeated together three will be used to make each section. In order to make the skeleton of the form a strip of heavy wood at least one inch thick and two inches wide and three feet long should be I IS MISSOURI AGRICULTURAL EXPERIMENT STATION, CIRCULAR 49. mortised into the three patterns every fifteen inches apart. The outer stick on each end of each form should be of 2x4 material. Cover each section with a heavy strip of sheet iron or with matched lumber running up and ciown. Any other bracing may be put be-tween the patterns that is found necesrary. As indicated by the .. diagram the patterns are all sawed in the radial line leading to the cen ter so that they will fit in a ci rcle. Building the Foundation.-Locate the silo at a place convenient to the barn. This will generally be within three or four feet of one end, or some door close to the mangers. Level off the gronnd, and with a string and nail mark out the circum ference of the silo with a radius at least one foot longer than the inner radius of the silo. Excavate within the circle at least four feet, keeping the dirt around the outer edge perpendicular. The foundation wall should be at least one foot thick to properly support a concrete silo, so as soon as the excavation is finished mark off another circle the exact size of the inner diameter of the silo, using the same center as above. Drive heavy stakes so that their outer edge will be exactly on the line of this circle completely around it and about two feet apart. The tops of these stakes should extend as high as the level of the highest part of the ground around it. Brace each stake from the middle so that it can not give. Bend one half inch planks around the outside of these stakes making an improvised inner form leaving the earth for the outer. The foundation should then be made of concrete, using crushed stone or very coarse gravel as the base of the mixture. The mixture recommended for the walls may also be used here. Care should be taken not to fill in concrete more than a foot in depth around at one time and this should be thoroughly tamped and worked with the spade until water stands on top, then allowed to set before an additional layer is added. The foundation should also be rein-forced by steel rods which may be bought for the purpose or by twisting together three or four strands of number 12 cable wires and laying them a foot apart as the foundation goes up. A spirit level should be used in order to get the foundation form at the same height and level all the way around. When the walls of the silo are complete the bottom should be laid. Put down a well-tamped layer of cinders or gravel about six inches deep and upon this put six inches of concrete. Plaster the surface about one-half inch deep with the same mixture used in smoothing down the walls. T l-I E REINFORCED CONC l<ETE S ILO. 11 9 Erecting the Walls.-As soo n as th e found at ion is finish ed th e for ms sho uld be se t in pl ace and the co nstru c ti on of the wa ll s begun . T he thi ckn ess of the wall shoul d be at least six inches and th e for ms desc ribed have bee n macle [or thi s thi ckn ess. In se ttin g up form s no spec ific direct io ns ca n be give n fo r th e erec ti on of So li d concre te s il o nea rin g compl e tion, with stag in g up on whi ch for ms res t. stagi ng. Th e acco mpa nyi"ng photograph will give so me id ea as to how this may be cl one but if th e build er is unce rtai n as to how bes t to kee p th e forms suspe nded he sho ulcl employ a carpenter for a day until th e stag ing is e rec ted. It is safer to use scaffoldin g both o n th e in sid e and outsid e to suppo rt th e form. \I\f hen in place the I20 MISSOURI AGRICULTURAL EXPERIMENT STATION, CIRCULAR 49. sections are bolted together as shown in the photograph. This holds them rigid. The first section of the wall will of course be built with the forms resting on the foundation, the inner one being barely on the inner edge of the foundation so that the inside waH of the silo will be perpendicular from the bottom up. As soon as the forms are in place and leveled, fill with concrete. Tamp the concrete well and work with a flat spade, especially next to the sheet iron on both forms, until the water rises on top. As SOOt"!. as level full the concrete must be left to set at least twenty-four hours. The forms may then be unbolted and raised. In building up the wall continual care must be exercisecl to keep it perpendicular. In order to accomplish this, do not raise the form to its full height but allow it to lap back on the solid concrete at least six inches at the bottom. Block and tackle of some description is used in raising the sections and in hoisting cemen t. Each time the form is raised grease the sheet iron surfaces with axle grease or soap before filling to prevent the concrete from sticking to the forms. The walls should also be reinforced at least every foot by means of steel rods which are laid horizontally inside the form or by twisted wire as previously described. This is a good place for old barb wire. When the forms are removed each time the inner and outer surfaces should be smoothed down with a board. This will be sufficient for the outside, but when the silo is completed the inner surface should be washed with a thin coat made by mixing one part cement and one part fine sand, This may be applied with a white-wash brush. Keep the sun out and wet the inside once or twice a day for a week. This makes a smooth and lasting inner surface. Mixing the Concrete.-The mixture which is practical to use It1 building a concrete silo is one part cement, two parts sand, to fOllr parts crushed rock or very coarse gravel. In mixing it is best to have a fairly accurate measure such as a wheelbarrow which ,~ill hold so many shovels or by counting the shovels of sand, gravel and cement used.!fhe best way to thoroughly mix material is to have prepared a w~n· jointed .. mixing-board, then dump convenient quantities of sand on the board. Put on the right amount of cement and thoroughly mix.with hoe or shovel. Put enough water on to make this sloppy, then dump on the gravel or crushed stone and turn at least twice with the shovel. The mixture is then ready to use. THE REINFORCED CONCRETE SILO. 121 TABLE NUMBER II MATERTAL NECESSARY FOR CONCRETE. Ht. Silo Inside Oiam. Thickness Cement- Sand- Gravel or Stone Feet Feet Wall·-Inches Bags Cubic Yards -Cubic Yards ----20 8 6 34 2% 518 20 12 6 55 4%' 87:2 20 15 6 73 5Y. 1I 25 10 6 54 4 8,J4.' 25 15 6 86 6Y. 13 25 20 6 121 9,J4.' 18 Y2 30 ,0 7 73 5)1! I1 ,J4.' 30 15 7 lIS 8Yz ' 7,J4.' 30 20 ~ 154 11% 23 Y. , 40 15 8 159 11- 24 ,J4.' 40 20 8 220 16 Y. 33 ,J4.' 40 25 8 28 3 2! Y2 44 Doors and Openings.~Openings must be left on the side of the silo next the barn. They should be placed no more than four feet apart, a convenient size being 2 x 2Yz feet inside measurements, the longer way up and down . The form is constructed so as to leave a shoulder on the inner edge of the opening which is two inches deep with a one inch jam. Reinforce each doorway with twisted wire completely around the opening to prevent splitting. The doors to fit into th ese depressions sh ould be made double of one inch matched lumber and stripped along the edges with tarred paper or felt in order to make air-tight joints. Generally the doors are set in place allowing the pressure of the silage to hold them. They may be bolted in place, however, by running a long bolt through the center of the door and a cross piece outside the opening holding to the outer edges of the silo. When in place the inner surface of the cloors is flush with the inner surface of the walls. A ladder leading up into the silo is necessary. To attach one to a concrete silo it is a good plan to set bolts a few feet apart on each side of the door openings as the wall is being built. Turn the bolts before the concrete sets completely so they may be removed and the ladder attached to them. A Simple Roof.-Silos should have a roof to protect the silage after feeding has begun. It is not necessary for the preservation of the feed before. Throw up rafters to the middle making a conical roof, and shingle Leave a trap door in the roof for the pipe when filling. 122 M ISSOU1H AC1UC"lJ LTU Ri\ L EXPERI M ENT S~L\TION, C IRCULA R 49. B ee f Ca ttl e Baril and S ton e S ilu 0 11 Co ll ~ge Farm, CO lll ' lJbi~ , \1 0. Thi s s il o is 2 0 ft . in di a m e te r, 40 ft. hi g h a nd ho ld s 240 to ns o f s il age. It is suite d o l1ly to large he rd s. It is re info rce ci with half-in c h iro n ro ci s , built into th e wall s. Note its p os iti o n in re la ti o n to th e barn. A favo rabl e locat ion o f th e s il o saves tim e a ne! la bo r in fee din g. In sec ti o ns o f t he s t a te wh e re buildin g· sto ne is ab und a nt it may be used Lo aclv a ntag·e in th e co ns ti·u c ti o n of s il os. H o we ve r, its fir s t cos t is g re ate r a ne! it is m o re liabl e to c rac k th a n is th e pro p e rly re info r ced co nc re te s tru c ture . 

The reinforced concrete silo

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