Chapter 6 Concrete 117
Finishing
Concrete finishing begins with screeding. Excess concrete is struck off
with a straightedge. This brings the top surface of the concrete to the proper
grade. The straightedge is moved back and forth across the top of the forms,
Figure 6-15. The next step is darbying. A darby, Figure 6-16, is used to level
and smooth the concrete after screeding.
In the next step, edging, edges are rounded over to prevent chipping.
This is normally done only on slabs with an exposed edge, such as drive-
ways and patios. In jointing, grooves are purposely placed in wet concrete
using a grooving tool. These grooves are called control joints. These joints
control the location of random cracking that may occur due to drying or to
temperature changes.
Floating removes imperfections and prepares the surface for the final
finish, Figure 6-17. It is done after edging and jointing.
screeding: A process
that removes excess
concrete and brings
the top surface to the
proper grade.
darbying: A process
that levels ridges
or fills voids left by
screeding.
edging: Creating a
radius along the edge
of a concrete slab to
prevent chipping
and to improve
appearance.
jointing: Making
shallow grooves in
concrete to control
cracking.
floating: Process
that removes
imperfections and
prepares the surface
for the final finish.
Figure 6-16. A darby is used to level and smooth
concrete. (Marshalltown Company)
Figure 6-17. A long handle attached to a float
allows the concrete finisher to level and smooth
a concrete surface from outside the forms.
(Marshalltown Company)
Figure 6-15. Screeding is done immediately after concrete is spread to level and
help consolidate concrete slabs.