Joints and imperfections in the forms are reproduced on the concrete
surfaces. Patches of honeycomb and rough places are left where the mortar
has run out of the forms or where the concrete has not been properly
placed. Such imperfections do not necessarily affect the strength of the
concrete, but they do detract from the appearance (see Fig. 14). Too of
ten the finishing of the concrete work in even the more important farm
buildings is neglected. With little extra trouble exposed surfaces can
be given a finish which will add to the attractiveness and hence the
value of the completed work. Rubbing off the form marks and pointing up
depressions or holes greatly improves the appearance of the work. The
rubbing may be done with a wooden float or hard-burned brick, using a
little sand and water as an abrasive and a 1:2 mortar for pointing up.
The surface can be worked best if the forms are removed within 24 hours
or before the concrete has set too hard. After the concrete has hardened
it may be necessary to use a carborundum block for rubbing.
A pleasing finish can be secured by scrubbing the surface with a stiff
fiber or wire brush, using plenty of water to wash off the loosened
particles. The work must be done while the surface is workable for if the
concrete is too green or soft the aggregate will break out and if too
hard the work can not be done effectively.
Artistic effects can be secured by picking or tooling the surface with
a bush hammer, toothed chisel, or pick. For such treatment the concrete
should be two or three weeks old to prevent breaking out the aggregate.
Other finishes may be obtained by etching with acid to expose selected
colored aggregates and by the application of stucco. The limitations
of the bulletin do not permit of a discussion of these more elaborate
treatments.