CONCRETE TANKS AND CISTERNS Concrete Water-Tanks. It is unquestioned that a tank built of concrete is not only more durable than one of wood, but is more sanitary. Many farmers have them installed in their barns, and tanks of this character answer the require ments in numerous manufacturing plants.
Two forms are required in the construction of a tank. One is needed for the moulding of the exterior, and a smaller one for the formation of the inner surface of the walls. Each form should be made of dressed boards without knots that will disfigure the surface of the concrete. For a tank of medium size, say 2 feet wide, 6 feet long, and 2 feet deep, the walls should be three inches thick. Allowance must be made there fore in the making of the two forms for a space of this width.
A flat surface perfectly smooth should be pro vided on which to place the forms. The smaller one is put in position first, as it is the one that will form the interior walls. It would be well, before placing the larger form, to measure care fully for the placing of it, by laying it on the platform over the smaller one and marking the corners, fastening the form so that it will not move when the concrete is placed. The inner form should be fastened also for the same rea son. Both forms should be greased.
The concrete should be prepared near at hand so that it can be placed quickly. The mix ture should consist of one part Portland cement, two parts sand, and three of gravel or crushed stone that will pass a quarter-inch sieve. Be careful not to make the mixture too wet. Tamp ing in layers of three inches is recommended for this work, each layer being followed up quickly with the succeeding one so that the fix ing may be uniform. The top is last leveled off and finished. Do not disturb the forms for a week or ten days. Then they may be removed,, and the drying continued.
dent to the reader. In the case of water troughs, this shape is more desirable from a utilitarian point of view, as it affords easier access. The first factor to consider is that of strength. The waterproofing of the tank can be attended to later. The best mixture for a tank is one part Portland cement, three parts of sharp sand, and five parts of gravel mixed with sufficient water to make the cement plastic or "sticky," but not thin enough to pour.
First dig the foundations, and place the foot ings for the wall and floor. Then mix the con crete as follows: For the foundation up to within four inches of the floor line, use one part Portland cement, three parts sharp sand, and two parts gravel that will pass through a one inch sieve, and four parts gravel that will pass a two-inch sieve. Mix thoroughly, and ram into position. If the tank is to be as large as 30 by 40 feet and 6 feet high, this course should be cov ered with a three and a-half inch course of one part Portland cement, three parts sand, and three parts gravel that will pass through a sieve of mesh. After this has hardened suffi ciently, build the falsework with a plank on both sides, and put in all pipe connections before be ginning to place the concrete for the walls, as any interference with the foundation after the walls are erected is not an easy matter to rem edy. Mix one part Portland cement, three parts sharp sand, and five parts clean gravel that will pass a one-inch sieve, and just enough water to make it sticky, and ram hard into position. Leave all the falsework in position for at least three days, to allow the concrete to harden. After removing the plank, plaster the exterior surface with a mixture of one part Portland ce ment and two parts sharp sand that has passed through a screen of one-fourth-inch mesh. This will give a finished effect, and will hold if the surface is wetted before application. A water proofing compound should be used in all the mixtures.