Part 3

It is always wise to order two or three extra barrels of cement, if the dealer is at considerable distance, as this avoids any possible trouble that a shortage might cause. Besides, any cement left over always comes in handy for repair work around the house or barn.

Forms for Concrete

Concrete is a plastic material and before hardening, takes the shape of anything against which or in which it is placed.

Naturally, the building of the Form is a most important item in the success of the work.

These Forms hold the concrete in place, support it until it has hardened and give it its shape, as well as its original surface finish.

Kinds of Forms

Almost any material which will hold the concrete in place will do for a Form. Concrete foundations for farm buildings require shallow trenches, and usually the earth walls are firm enough to act as a Form.

Molds of wet sand are used for ornamental work. Frequently colored sands are used for this purpose, providing both the finished surface and color to the concrete ornament.

Cast, wrought or galvanized iron is used, where an extremely smooth finish is desired, without further treatment upon the removal of the Forms. Forms made of iron are more easily cleaned, and can be used a greater number of times than those of wood. Rusty iron, however, should not be used.

By far the greatest number of Forms are made of wood, owing to the fact that lumber in small quantities can always be obtained.

Requirements of a Good Form

Plan your Forms so there will be no difficult measurements to understand. Make as few pieces of lumber do the work as you can, and do not drive the Forms full of nails. If you do the Forms will be difficult to take apart without splitting.

Forms must be strong enough to hold the weight of the concrete without bulging out of shape. When they bulge, cracks open between the planks and the water in the concrete, with some cement and sand, will leak out. This weakens the concrete, and causes hollows in the surface which look badly after the Forms are removed.

Forms which lose their shape after being used once can hardly be used a second time. A part of the erection cost of Forms is saved if the Forms are built in as large a section as is convenient to handle. This saving applies to their removal, as well as to their setting. Consequently, the lightest Forms possible, with the largest surface area, are the most economical.

How to Plan Forms

The first consideration in planning Forms is the use to which they are to be put. Neglect of this point means waste of money and time. If they are for work afterward to be covered with a veneer coat, the finish of the surface is of small consideration, while the alignment of the Form is all-important.

If a tank or retaining wall is to be built, the fact that the Forms are not in exact alignment will hardly be noticed.

In planning Forms for large structures, the oftener each section is used, the less the cost. You save money if they are rigid in alignment, and well surfaced. In other words, if you count on using your Forms over and over again, the more nearly perfect they are, the more often they can be used, and the cheaper they become.

If Forms are to be used only once, as is generally the case on the farm, they should not be nailed so securely as to prevent their being readily taken apart, and the lumber used for something else. If often pays to put them together with screws. If nails are used, do not drive them home.

Care Needed in Selecting Lumber for Forms

The selection of lumber is of importance. If the Forms are to be used over many times, surfaced lumber, matched, tongued, and grooved stuff, free from loose knots, is an economy. If, however, they are to be used only once, almost any old plank will do. By nailing a board on the outside of the cracks or over the bad knot, and filling with a little clay, the Form is made tight.

Green lumber is preferable to kiln-dried or seasoned stuff. Seasoned stuff, when wet (either by throwing water on the form before placing the concrete or by absorbing the water from the concrete) warps, and the shape and tightness of the Form are damaged.

Originally only surfaced lumber was used for Forms, dependence being placed on it for giving a finish to the work. While to-day other than smooth surfaces for concrete are the fashion, surfaced lumber has some advantages. The Forms fit together better and are easier to erect. They are more easily cleaned. They are easier to remove. All these items reduce the cost of the work. The saving effected will of course depend on the difference in local price between finished and rough lumber.

How to Clean

Particles of concrete stick to the Forms. In order to prevent this, give the surface next the concrete a coat of oil or soft soap. Linseed, black or cylinder oil may be used. Never use kerosene.

Before erecting, paint the Forms with the oil or soap. Then carefully protect them from dust or dirt until erected. Upon removal, immediately clean off all the particles of concrete sticking to the surface. A short-handled hoe will take off the worst, while a wire brush is most effective for finishing. Be careful not to gouge the wood in cleaning, as it will spoil the surface of your next section of concrete. It will not be found necessary to repaint after each time of use. Watch the surface and repaint if it appears dry in spots.

If chips or blocks of wood fall inside the Forms while erecting, carefully remove them. The space inside the Forms is intended for the concrete; and care should be taken to see that only concrete is placed there.

The necessity of Forms presents a problem calling for the use of that ingenuity for which the farmer is justly famed. Forms can be economically placed in so many ways that only one example will be given. A foundation Form in place is shown in the photograph. Note the simple and easy method of bracing. Also note how lumber is saved from cutting by allowing the sides to project, as well as the studding.

For this building, 18 by 24 feet, trench 18 inches wide and 2 feet deep—total cost of setting forms $4.00. The lumber was all on hand and can be used again.

How to Place Concrete

No time should elapse between the “mixing” and the “placing.” Directions for placing must of necessity be general, and the farmer must use his own judgment as to how to handle this part of the concrete work, in connection with whatever particular job he has on hand. The important thing to remember is, that the materials should not separate in placing.

You may shovel the concrete off the board directly into the work; you may shovel it into wheelbarrows, wheel it to position and dump, or you may carry it to the proper place by buckets and hoisting apparatus.

Directions for Placing

Ordinarily speaking, concrete should be deposited in layers about 6 inches thick.

After placing concrete in the Form, it should be “tamped” _lightly_ with a wooden or iron tamper (or rammer) until the water shows on the top and no stones are left uncovered by mortar.

In order to obtain a smooth face on the concrete, the mixture should be carefully “spaded” immediately after “placing”—on the side next to the Form where the finished concrete will be exposed to view. By “spading” is meant the working of a spade or a beveled board between the concrete and the side of the Form, moving it to and fro, and up and down. This forces the large stones away from the boarding, or Form, and brings a coating of mortar next thereto, thus making the face of the work present an even, smooth appearance.

The Necessary Tools

On certain jobs—as, for instance, in the case of a 6-inch silo wall—a spade cannot very well be used, on account of the narrowness of the concrete section. In this event, use for surfacing, a thin wooden paddle, made from a board 1 inch by 4 inches, and gradually sharpened to a chisel edge at the end. The sharpening should be on one side only, and in using this paddle place the flat side against the Form, as shown in illustration.

When the mixture is a _dry_ one, great care must be used in this “spading” or surfacing, in order to obtain uniform results, but in the case of a _wet_ mixture, spading is only required as an added precaution against the possibility of voids in the face of the work, and in many cases it is not necessary at all.

Protection of Concrete after Placing

Green concrete should not be exposed to the sun until after it has been allowed to set for five or six days. Each day during that period the concrete should be wet down by sprinkling water on it, both in the morning and afternoon. This is done so that the concrete on the outside will not dry out much faster than the concrete in the center of the mass, and should be carried out carefully, especially during the hot summer months. Old canvas, sheeting, burlap, etc., placed so as to hang an inch or so away from the face of the concrete will do very well as a protection. Wet this, as well as the concrete. Often the concrete Forms can be left in place a week or ten days; this protects the concrete during the setting-up period and the above precautions are then unnecessary.

Points to Remember

It may be well, in summing up, to emphasize the following points:—

1st. The materials must be perfectly clean. 2d. The mixing must be in proportions carefully determined. 3d. The mixture must be used while absolutely fresh.

Good results cannot be obtained unless you use a good cement, nor will the work be at its best unless care is taken in the selection of clean sand and clean stone.

Among the uninitiated, there is an all too prevalent idea that anything is good enough for the making of concrete. Some will tell you that sawdust, shavings, mud, clay, etc., will do to complete the mixture, but the absurdity of this notion will very soon become evident to anyone who neglects the precautions which have been above pointed out.

Reinforcement

_Principles involved_

Concrete and steel render valuable assistance to each other in the support of heavy burdens. On a solid foundation, loaded from above and thus under direct pressure, a concrete column will withstand the strain of an enormous load. A much smaller load so placed as to cause stretching or bending toward one side of the same column may cause it to snap off, for concrete is strong, but brittle. On the other hand, steel is tough and elastic. In the form of rods or wire, steel withstands massive loads that tend to stretch it, and thus displays a kind of strength directly opposite to that of the plain concrete column. In modern construction these two valuable properties of concrete and steel are utilized by combining them in what is called reinforced concrete. With steel properly buried in the concrete, the column withstands not only the load which might otherwise snap it, but one many times larger, and even though it is applied at any place along its length.

Reinforcement, therefore, is steel in the form of rods, bars or wires, buried in concrete to take up and to withstand the strains which tend to stretch or to bend the concrete. A concrete fence post is merely a small concrete column. Reinforced, it easily stands the strain from usage in a fence line.

The value of reinforcing concrete posts properly may readily be seen in the figure. If a load (L) is raised so that its weight is supported on one side by a wooden post, the post will bend. The fibre in the wood on the side away from the load may be tough and elastic enough to prevent the post from breaking, and when released the post will spring back into its former position. In the third figure a No. 9 wire (W) is fastened securely to the wooden post at the top and at the ground surface, and is supported along its length by the struts (S). If the same load is applied, the post will not bend, because the wire takes up the bending or stretching strain. This is precisely the case with the reinforcement in a concrete post. Supported along its length by the concrete, the wire (W) or steel in other shapes takes up the bending or stretching strains. Since the load which causes bending or stretching may come from any direction, concrete posts are reinforced on every side; otherwise they might break in a manner somewhat similar to that in which the wooden post bends when the reinforcement is not on the proper side of the post.

In the effort to be safe it is a common fault to insert more reinforcement than is absolutely necessary. This adds needlessly to the cost, for concrete becomes stronger as it grows older.

Kinds of Reinforcement

With regard to the roughness of the outside, metallic reinforcing materials are divided into two classes, smooth and corrugated or deformed. The general result of the many tests carried on in testing laboratories seems to indicate that in strength of bond, if the concrete is sufficiently rich and well mixed, smooth surfaces give satisfactory results. Two kinds of reinforcement are much used—bars and wire.

_Bars._—Round bars three-sixteenths or one-fourth of an inch in diameter are the size and kind most used on the farm. The stock on hand at blacksmith shops and hardware stores is generally from steel that stretches too easily and therefore is not the best for reinforcement. Companies which make a specialty of reinforcing materials can furnish both rods and bars which stretch only under very large loads.

_Wire._—The development of the wire fence has produced a material well suited for reinforcing purposes. Of equal size, such wire will produce a stronger reinforcement than the material above described. In order to obtain straight wire of the necessary length, the coils ordinarily placed on the market should not be straightened out. Straight wire can be obtained from dealers in the same manner as baling wire; that is, either single or twisted into two or three-ply cables, and of the length desired. The plain, ungalvanized fencing wire is the proper kind, for galvanization adds nothing to the strength, and the metal will not rust when incased in the concrete.

Concrete Sidewalks and Floors

Concrete floors are nothing more than sidewalks of large size, and are formed by casting slabs in place.

The description given is an economical and practical method of laying sidewalks or floors, easily adapted to any use where concrete is found advantageous. This description will therefore apply not only to the building of sidewalks, but to all flat surfaces of concrete resting on the ground.

Lasting Qualities

Concrete floors must remain hard and in position to be permanent. To accomplish this, good materials must be used, and proper methods of mixing and placing must be followed. Only in this way can settlement cracks, upheaval by frost or roots of trees, contraction cracks, crumbling, and general failure be avoided.

Settlement Cracks

To avoid settlement cracks, thoroughly ram the ground after excavating for the foundation. This gives a solid bearing to the concrete slab.

Upheaval by Frost

To prevent upheaval by frost a foundation formed of crushed stone, hard furnace cinders, brick bats broken to about a 2-inch size, broken tile or any other hard porous material, should be laid in such a way as to obtain perfect drainage. Never use ashes.

If freezing occurs, room is in this way provided between the pieces of stone for the expansion of the ice.

If this foundation is placed in clay soil, side outlets or blind drains of tile should be provided at points along the walk where they are necessary, leading into holes filled with cinders or crushed stone, which will allow the surrounding earth to soak up the accumulated water. Clay soil holds the water collected in the drainage foundation, and if it becomes entirely full of water, the ice formed during freezing weather will upheave the walk.

Upheaval by Tree Roots

Upheaval by tree roots can be easily avoided by cutting out all roots which run under the pavement at a less depth than 18 inches below the surface of the ground.

Contraction Cracks

Cement concrete expands and contracts by changes of temperature in the same way as steel. It is, therefore, necessary to cut joints which will allow for this expansion and contraction. The concrete must be cut entirely through to the bottom of the slab with a trowel, cleaver or other instrument, the joint formed being from ⅛ to ¼ of an inch wide. Blocks formed in this way should not be greater than 6 feet square (36 square feet).

Scaling or Crumbling of the Surface

The principal causes of scaling or crumbling surfaces are improper mixing, drying out before the cement has thoroughly hardened and the use of bad materials.

Cement needs water not only when mixed, but after being placed and tamped, and until it has entirely hardened. If concrete is not kept continually wet until hard, it is weakened, and the surface of such a walk scales or becomes soft and chalky.

Specifications

DRAINAGE FOUNDATION

Stake out the lines of the walk, or dimensions of the floor. Excavate to a depth of 16 inches, ram and tamp the ground thoroughly and evenly and fill in 12 inches with clean large cinders, broken stone, pebbles, brick bats, broken tile or other material selected. Place in position wooden forms made of 2 by 4’s, these 2 by 4’s to be set on edge and held in position by stakes firmly driven in the ground, the top edge to be located so as to accurately outline the established grade or slope of the walk or floor.

A walk should be higher in the center, or at one edge, to insure the water running off. This slope should be ¼ of an inch to the foot.

SELECTION OF MATERIALS

Particular attention must be paid to the selection of the materials and their mixing.

The concrete should be composed of gravel or crushed stone all of which will pass through a ¾-inch mesh screen, and be collected on a ¼-inch mesh; sand, free from loam and preferably coarse, and a grade of Portland cement guaranteed to meet all the requirements of the Standard Specifications as adopted by the American Society for Testing Materials and the American Society of Civil Engineers.

PROPORTIONS

The strength of the slab is not always governed by its thickness. The greater strength is obtained by properly proportioning the gravel or crushed stone, sand and Portland cement, so that all the spaces between the stone are filled with sand and cement.

The Portland cement, sand and gravel or crushed stone should be mixed in proportions, if the sand is not very coarse, of 1: 2: 4—which means, 1 part Portland cement, 2 parts sand, 4 parts gravel or crushed stone, all passing a ¾-inch mesh and all collected on a ¼-inch mesh. If the sand is coarse and the crushed stone or gravel well graded in size of particles, it may be mixed in proportions of 1 part Portland cement, 2½ parts sand, 5 parts gravel or broken stone. All proportions are measured by volume.

Bank run gravel is often used for sidewalk work, particularly where a good bank can be found on the farm. It is safer, if this material be used, to screen out the pebbles, using them as stone, measuring the quantities of stone and sand as described above. Concrete should not be laid in freezing weather.

CONSISTENCY OF CONCRETE

Mix the concrete as described on page 15 to a consistency that when tamped, it will not quake, but it should be sufficiently wet so that some moisture will rise to the surface under tamping.

PLACING

Divide the walk by setting forms at right angles to the side forms. The cross forms can be made of 2 by 4’s. These provide for expansion and contraction joints. Hold these forms in place by driving stakes through the foundation into the ground on the opposite side from where the concrete is to be placed. Spread the concrete over the drainage foundation to the thickness of the walk or floor, and in slabs not over 6 feet square. The thickness of a walk should be 4 inches, a driveway 6 inches, a floor over which a wagon may be driven 6 inches, and all other floors 4 inches.

Fill in every other slab, placing enough forms to use up all the concrete mixed in one batch. No batch should stand longer than one half hour before being placed.

Tamp the concrete thoroughly. Use a template, with ends resting on the side forms, and cut to a curve to give the walk the necessary crown. The concrete should be tamped so as to conform to the curve of the template. If one edge of the walk is made higher than the other, use a straight edge resting on the side forms. Tamp the concrete to conform to the straight edge.

Mix another batch of concrete, remove the cross forms and place the concrete between each slab, forming a continuous walk. Use the template or straight edge and tamp as before. Immediately after placing the closing slab, work a straight trowel or knife down through the entire depth of the concrete between each slab, thus insuring a perfect contraction joint. Smooth the surface with a wooden float.

A neat appearance may be given the contraction joints by running a jointer along the top, thus smoothing the edges. Do this before the concrete gets too hard. The sides of the walk may be smoothed in the same way by use of an edger.

When the concrete is nearly hard go over the surface with a piece of oakum or a stiff brush, removing the marks of the float and giving a good even wearing surface which will not be slippery. In using oakum or a brush be careful not to remove the larger pieces of stone. If surfacing in this manner disturbs the particles of stone and roughens the walk to too great an extent, allow the walk to harden a little more before finishing in this way. At the end of each day’s work see that the last slab is entirely filled and finished.

All interior floors, such as floors of cellar, barns and stables require no contraction joints. They are made by laying a solid continuous sheet of concrete. All outside floors should have contraction joints forming slabs not over 6 feet square. These are provided the same as in sidewalks. A feeding floor is formed merely by sidewalk pavements set side by side. Instead of using a template for crowning the surface, use a straight edge, each end resting on the extreme outside forms to give a slope to the feeding floor. Contraction joints for exterior floors are formed in the same way as for sidewalks. The concrete is also placed in alternate slabs and finished in the same way as sidewalks. When completed the walk or floor must be continuously protected from the rays of the sun and from the wind for at least three days, so that it will not dry out at any time. This can be easily done by covering the concrete when it is hard with hay, straw, or old carpet. This covering should be thoroughly soaked with water, and kept wet for three or four days or longer if economy will permit.

While the walk or floor is hardening it should be so protected as to prevent persons or animals from disfiguring the surface by walking on it.

A Foundation Gutter and Walk

Foundation gutters catch the water from off the rain-beaten side of the building, quickly carry it away, and, by preventing “seepage,” keep the cellar, basement, or ground-floor dry. In sloppy, muddy weather, they also serve as convenient walks around the out-buildings.