Concrete on the Farm

New Zealand Journal of Agriculture, Volume 62, Issue 3, 15 March 1941, Page 157

Concrete on the Farm

... By

J. A. S. MILLER,

Instructor in Agriculture, Wellington.

Full Description Of ** How To Use Concrete For Posts and Troughs

: Having dealt in the previous E E article with mixing concrete E E and the construction of floors E E and paths, the author con- E E eludes by discussing the manti- E E facture of concrete fence posts, E E water troughs and buildings. E "nilllllllliilllliillllliliiiiiiiiiiinti 1111 i lIIIIIIIIIIIIIMIIIIII 111

Fencing Posts Concrete posts are rapidly gaining in popularity for obvious reasons. They are durable, neat in appearance, and relatively cheap. Their resistance to fire is a very useful characteristic. There are numerous shapes' and sizes of concrete posts, but for general duty intermediate posts, dimensions of 6 ft. x 4 in. x 4 in. are eminently suitable, but no matter what particular style of post is chosen adequate reinforcing is essential. It is not merely a matter of bundling into the mould several pieces of old iron and imagining that this is all that is required. Reinforcing rods near the centre of the post are quite useless. Actually, the nearer

the exterior of the post the better, provided the rods are not exposed and thus allowed to rust. In general practice, a depth of J in. from the outside of the post is the most suitable. It is generally desirable to prepare intermediate posts in a gang mould

one capable of turning out six or more posts at a time. Apart from saving time, it enables the most efficient use to be made of one mix of concrete. For example, a one bag mix will make six 6 ft. x 4 in. x 4 in. posts.

The construction of a suitable mould should present no great difficulty, but for the sake of efficiency it should be made as durable as possible. Only wellseasoned, dressed Oregon should be used, and the minimum thickness of the timber should be ' 1 in. Good Baseboard Essential ‘ A good solid baseboard is essential, and on this are constructed the neces-

sary cleats and blocks which support the mould sides. Care must be taken to prevent the side members from bulging when the concrete is being introduced, and to do this blocks should be fitted on extreme outsides of each of the outer members, while the inner boards are held in place by a trans-' verse slotted board, which fits over them.

In placing the concrete, fill one mould at a time. First spread about J in. of concrete evenly over the bottom and ' place the reinforcing rods (which should be 2 in. shorter than the post) f- in. from the inside edges of the mould, pushing them into the concrete to a depth of i in; for 4 in. x 4 in. posts, i in. steel rods are used. Fill up until j- in. from the top of the mould, and

place the other rods, sinking them to a depth of i in., J in. from the edges.. Complete the filling, allowing some extra (1-8 in.) on top to account for the shrinkage. After half an hour beat the surface of the concrete with a piece of wood having an edge of one inch. The material will then resemble a jelly, and it will be noticed that the surplus water and scum has oozed to the surface. This should be scraped off to the level of the mould sides. When the concrete is about eight hours old, cover with damp bags and leave until it is decided to remove the posts from the moulds— matter of two or three days, depending on whether the conditions are warm or cool. The posts thus removed should still be covered with damp bags for four or five days more.

It should be noted that it makes no difference to the initial set whether normal or rapid-hardening cement is used. It is in the final stages that rapid hardening cement indicates its usefulness. Using this, cement posts may be put into commission after 10 to 15 days old, depending on the weather. Ordinary cement requires 28 to 38 days. To reduce the time required in the moulds, calcium chloride may be used as an accelerant.

After the posts have been removed from the moulds the mould should be well washed and, when dry, treated with a thin mineral oil, such as crankcase drainings. This treatment should also be applied before the moulds have actually been used.

Attaching Wires

Wires may be attached to the posts in a variety of ways.

. (a) By running the wires through holes in the post.

(b) By means of half staples which can be bent over the wires when the latter are in position.

(c) By double staples, placed parallel with the wires (that is, one above and one below) with a length of wire running through.the eyes of the staples and thus holding the fence wires in position.

(d) By using an improvised staple, which consists of a length of No. 8 gauge wire which is bent so that one leg is about 2 in. long and the other about 5 in. This grips the wire and is driven through the post in 3-8 in. holes running at right angles to the line of the fence wires. The longer leg of the

staple is then bent down at the back of the post, sometimes into a groove specially moulded into the post. This is fast becoming the most popular type of wire fastener for use with concrete posts. ' u Mixture for Posts The concrete mixture required for ordinary fence posts consists of gravel having a maximum diameter of 3-8 in. A one-bag mix should be used, and the aggregate should be in the proportion of 3 cubic feet of 3-8 in. graded gravel measured loose to 2 cubic feet of loosely measured sand. If the sand and gravel are already mixed in suitable proportions, only 3f cubic feet of

this aggregate need be used. If sand alone is used, take 5 cubic feet. The mixing water should not exceed 7 gallons for this mix. For corner posts and straining posts, only single moulds will be required, as relatively few of these are needed in proportion to the number of intermediate posts. Corner posts need not have dimensions greater than 6 ft. 6 in. x 6 in. x 6 in., while straining posts for straight fence lines can be built to a size 6 ft. 6 in. x 6 in. x 4 in., and the moulds can be made accordingly. With the above types of posts, struts are generally necessary, and these may be made from concrete to a size of

7 ft. x 4 in. x 3 in. To receive the upper end of the struts a .slot should be moulded into the post by using a triangular block of wood at the bottom of the mould and in the required position. The lower end of .the strut should be supported on a foot constructed from concrete 1 ft. x 6 in. x 3 in. thick. Reinforcing should consist of 5-8 in. steel in the case of corner posts, 7-16 in. for strainers, and i in. for struts. The following table is useful in making the above posts:— "

Water Troughs Concrete as a material for water troughs cannot be excelled for the reason that it is most durable, absolutely waterproof if properly constructed, and requires no maintenance.

The troughs to be constructed on a farm will vary according to the type of stock carried and the purpose for which they are required. Horse troughs are usually of rectangular design and of robust construction, but perhaps the

most useful type for general utility is one constructed in a circular form.' The building of such a trough can be re- . peated any number of times, as the moulds are generally made from corrugated iron specially curved to suit the dimensions of the mould. The following data covers ’ the materials necessary for the construction of a trough capable of supplying 100 cows or 500 sheep, even with , a slow feed pipe.

For the inner mould two 9 ft. sheets of . corrugated iron are required, and these should be rolled to give a clear inside diameter of 5 ft. 2 in., while for the outside, two 10 ft. sheets rolled to give a diameter of 5 ft. 10 in. are necessary. These lengths will provide an overlap of sufficient length to allow for joining. The sheets should not be more than 21 in. high. The components of the mould are bolted together with stove bolts at the overlap, allowing sufficient bolts to give the necessary rigidity. For convenience, wooden handles should also be fitted near the joints to allow easy removal of the moulds. These handles are merely pieces of wood 2 in. x 1 in fixed vertically. To construct the trough, lay the floor and allow it to set. Strips of tarred felt or old sacking are laid round the base of the walls and the mould set up. The inner mould is first placed and then wrapped round with heavy gauge wire netting, using a few vertical strips of wood If in. thick to space the netting away from the mould. As soon as the outside mould is set up the concrete can be poured in, the spacers being removed as the mould fills. Careful tamping is essential to ensure a waterproof job. The moulds may be removed after three days with rapid hardening cement, ; and after seven days with ordinary cement. A ball and chain valve should be used to control the water feed, the pipe of which is either set into the floor or taken up over the wall of the trough and down the bottom by means of suitable fittings. The materials required are as follows: J . ■ Cement, 5 bags. Sand, 11 cubic feet. Gravel, 20 cubic feet (1-8 in.-3-8 in.).

With each bag of cement, mix 14 gallons of sand and 25 gallons of gravel, using only 6 gallons of mixing water. However, most men have their own ideas about constructing a trough. The main points to be considered are suitable concrete mixtures and careful reinforcing. Large Troughs Large square troughs can be constructed for use in watering four paddocks simultaneously. Such troughs should have internal dimensions of at least 8 ft. x 8 ft., and should be 2 ft. deep. The foundation' should be carefully prepared, as the weight of the trough will be considerable. To ensure rigidity, it is desirable to reinforce the whole structure, floor and sides. This is best carried out by using prepared expanded metal or by means of 3-8 in. steel rods. Whatever method is adopted, the chief consideration is that of carrying the reinforcing from the floor right up the sides. The floor is first filled in with highgrade concrete to a depth of 3 in. to 5 in., and the side forms (which have been constructed previously) erected. These forms should be well built from Pinus radiata or other suitable timber, and the sides well braced to prevent bulging while the concrete is being introduced. It is desirable to do all the concrete work at the one time, as it is difficult to bind new concrete with old. In from 12 to 14 hours, depending on weather conditions, the forms may be removed and the sides of the trough rubbed with a wooden float to obtain a smooth surface. Plastering is unnecessary if a good. concrete mix has been

used. In any case, it is essential to prevent the concrete from drying out too quickly, and to this end the sides should be covered with wet bags and some water allowed to remain on the floor. • During the construction of the floor the water inlet pipe should have been introduced somewhere near the centre, and, where practicable, a 3 in. to 4 in. glazed earthenware bend should be provided to allow flushing. The inlet pipe, S- in. to 1 in. diameter, depending on ’the pressure of the water supply,

should protrude about 6in. from the floor of the trough and have an elbow screwed to it. The ball cock with ball removed is then connected and a suitable length of chain to the ball, which is then able to float on the surface of the water without fear of damage to the valve below. A rubber-lined wooden plug, suitably weighted' and fitted with a handle, should be inserted over the drain bend, and this can be removed from time to time to clear away any sediment. Pig Troughs A suitable pig feeding trough is comparatively simple to construct and is useful for all feeds except skimmilk, the acids from which are liable to attack concrete. Suitable reinforcing is also required,, as in the case of other troughs. . . A useful trough for watering pigs has an inside measurement of 3ft. x 2 ft, x 9 in. deep. The trough is divided into two sections by an inverted. concrete box 2 ft. x 1 ft. x 9 in. deep which houses the ball cock and thus prevents any damage to it. The sides of this inverted box are slotted to allow a free flow of water. The concrete, is : sufficiently reinforced throughout, and is about 2 in. thick. Concrete Drains The use of concrete for gutters is well recognised, and concrete pipes for drainage purposes are • very widely used, especially where pipes of larger , diameter are required! Concrete pipes for farm sewerage ■purposes can be prepared and laid in the following manner. A cylindrical form is prepared, the diameter of which is that of the inside of the pipe required. This form is constructed from : heavy gauge sheet iron, and is split from one end to the other by a long 'tapering cut. When the form is in use : this cut is filled by means of a long slide shaped to the same taper, so that when it is inserted the form has an even dia-

meter throughout.

The trench is dug as for laying ordinary drain pipes, and about 2 in. of concrete placed on the bottom. With the slide inserted, the form is laid above the layer of concrete. More concrete is

then poured on top of the form, adequate ramming going on during this time until there is a layer of about 2 in. of concrete right around the form. This is allowed to set for about two hours, after which the slide of the form is pulled out about 3 in. to allow the easier removal of the mould. After from six to twelve hours the slide is withdrawn completely so that the walls of the form collapse. A 2 in. layer of concrete is placed in the trench as before, and the form can now be pulled out until only about 3 in. of it remain inside the completed section. The slide is replaced and the concrete poured on until the next section is completed.

Pipes of any diameter can thus be made, although the construction of the form may present some difficulty. About 24 feet a day can normally be laid, the form being about 8 ft. long. No reinforcing is required unless there is to be heavy traffic over the drain, in which case the concrete must also be made thicker. The trench can be filled in immediately after the removal of the mould, and this has the advantage of preventing too rapid drying out of the concrete. Junctions and changes in direction are made by means of a concrete box into which the pipes run.' These boxes are covered by a concrete lid, which can be removed to clean out the drain in case of blockage. Concrete Buildings Concrete buildings are constructed on two main principles, namely, concrete laid on the spot and concrete made into and used as “bricks.” Of the two, the former is more often used in the construction of out-buildings, while the

latter is used in the-construction, of dwellings, the reason being that the “bricks” are usually made with a hollow section and thus allow for ventilation and provide a double wall. In the construction of walls of solid section, the general practice-is to erect piers of considerable strength- and then fill the 6 ft. intervals between them with : a “curtain” wall. Depending on the height of the walls, the piers may be 6 in. x 6 in. or 8 in. x 8 in. in cross section. These are spaced at 6 ft. intervals, being inserted into the ground to a sufficient depth to ensure rigidity. The reinforcing of the rest of the wall is then bonded into them, a longitudinal slot running down each side for the full length of the wall to allow of bonding of the “curtain” walls. Rigid forms are then applied to give a normal wall thickness of 3 in. and the concrete poured in. The resulting wall is usually flush on the inside of the piers, while the outside presents a series of projecting ridges. If the concrete is well prepared, plastering of the finished walls is unnecessary, the concrete being well rubbed while in the “green” state. Where concrete “beams” have to be constructed, as above doors and windows, great care must be taken in the prepartion of the. reinforcing. As stated ■ in an earlier part of the article, pure concrete cannot withstand bending, although it can resist considerable compression. A beam supported at each end is subjected to two distinct stresses tension on the lower side, and compression on the upper. Thus, the reinforcing must be concentrated at the lower side of the beam where the tension occurs. Less reinforcing is needed on the upper side, where the stress is that of compression. For example, a 20 ft. concrete beam to carry a distributed load of 14 tons should be 15| in. deep and 8 in. thick while the reinforcing should consist of two 3-8 in. steel rods at the top and four J in. rods at the bottom. Suppose, however, that the beam is supported at intervals along its length on piles. Then, at each point of support the beam is bent in the opposite direction, that is, compression occurs on the lower side, while tension occurs on the upper. Hence, at this point, the reinforcing should be concentrated on the upper side, of the beam. If concrete columns are built, say, to support a floor, the reinforcing must be so arranged as to prevent lateral distortion of the column. An. unreinforced concrete pillar supporting a

heavy load would have a tendency to become barrel shaped. To overcome this tendency, wire stirrups are ■ used to bind the. reinforcing rods. For example, a column shorter than 8 ft. 10 in. x 10 in. reinforced by four f in. rods would have stirrups of No. 8 gauge wire 8 in. apart along the length .of the column. Such a column would support a load of 14 tons. X ■ Acknowledgment The author wishes to acknowledge the assistance given by Mr. J. R. Marks, A.M.Inst.C.E., M.N.Z.Soc.C.E., of Wilsons (N.Z.) Portland Cement Ltd., , Auckland, in compiling this article.

Class of Post. Dimensions. Reinforcing. Approximate weight of finished post. Number of posts to each bag of cement Intermediate posts 6ft. x 4in. x 4in. i in. steel 95 lb. 6 Corner posts . . 6ft. 6in. x 6in. x 6in. i in. steel 245 lb. 2 2/3 Straining posts 6ft. 6in. x 6in. x 6in. f in. steel 2451b. 2 2/3 on straight . . 6ft. 6in. x 6in. x 4in. 7/16 in. steel 160 lb. 4 Struts . . i in. steel 160 lb. 4 Struts .. 7ft. x 4in. x 3in. 7ft. x 4in. x 3in. 1 in. steel 85 lb. 7