Page 71 - Masonry and Concrete

Concrete Construction Techniques
70 CHAPTER THREE

spread the gravel aggregate over the slab
by hand or shovel so that the surface is
completely and uniformly covered with a
single layer of stones. Embed the seeded
aggregate in the fresh concrete by tapping
with a darby, a wood float, or a flat board
until the aggregate is completely and uni-
formly covered by the concrete (Figure 3-
34). Be careful not to embed the aggregate
too deeply, and keep the finished surface
flat. When the concrete has cured enough
to bear the weight of a person kneeling on
a flat board without leaving marks in the
surface (anywhere from one to three
hours, depending on conditions), begin
brushing away the top surface of the con-
FIGURE 3-30 crete to expose the seeded aggregate. First,
lightly brush the surface with a stiff-bris-
Wood float. (Photo courtesy PCA).
tled nylon broom. Work carefully so that
you do not dislodge the stones. If dislodg-

FIGURE 3-31
Broom finish.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.