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:—