CONCRETE BUILDER

Building Black-Colored Concrete
Tennis Court with White

Mortar Playing Lines

By ALFRED SIMMONS

Foreman, Bulley & Andrews, Concrete Contractors, Chicago, Ill.

court which we built for the Uni-

versity of Chicago has several fea-
tures that will interest concrete contrac-
tors. The plans, which were prepared
by the building and grounds department
of the university, called for black con-
crete topping that would prevent glare
from bright sunlight. The playing lines
were to be of white cement mortar which
would not need constant repainting. The
surface was to have a mat- or canvas-
like finish. The drainage system was to
be different in that surface water was to
be collected and carried away without
allowing it to run over the edges of the
slab or over the next court.

All of these features interested me,
and I could see that here was a chance
to build something new in tennis court
construction.

at a black-colored concrete tennis

Construction Details -

N beginning this work we set stakes
(about 10 ft. apart both ways) to
the finished grade which allowed for a
slope of 2 in. to one side. Next we
laid 6-in. drain tile around the outside
of the court, connecting it to the storm
water drain. About 8 in. from the edge
and near the net post on the low side of
the court, we built up a riser pipe to pro-
vide an outlet for the integrally formed
gutter along the outer edge of the con-
crete slab. Then we placed the base
for the net posts. This was done early
so that the forms could be taken off when
we built the slab.

After the surface of the old court was
removed to 5 in. below the top of the
grade stakes, we set the forms which con-
sisted of 2-in. material. They were set
along the single court playing lines, con-
tinuing out to the edges of the court.
In this way, the concrete slab was built
in sections corresponding to the play-
ing lines.

  

Alfred Simmons

To make the grooves for the white
concrete playing lines, we used 2 by 2-in.
wood strips beveled on one side to per-
mit easy removal. These were lightly
nailed to the form boards. For the
double court lines, the 2 by 2’s were
notched into the top of the cross forms
and supported in between on small
wooden stakes. Later, when the strips
were pulled out, we drove the stakes
down and filled the spaces with white
portland cement mortar.

All sections of the court were rein-
forced with large-mesh metal reinforce-
ment weighing 78 lbs. per 100 sq. ft.
To tie adjoining sections of the concrete
together and keep them even, we placed
¥%-in. round bars, 30 in. long, about 3
ft. apart in all construction joints. The
work was laid out so we could keep
going without having to work over any
of the completed slabs before they were
at least two days old.

For the concrete in the 5-in. slab, we
used a 1-214-314 mix for the base and a
1-214 mix for the top. To get the color
in the topping that the inspector wanted,
we. used 1 gal. of specially prepared
liquid black mineral oxide to each sack
of portland cement. We placed concrete

 

that was quite stiff yet workable. I

mean “placed” not “poured’’ because the
concrete we used wouldn’t pour, but re-
quired placing. I have found that quite
stiff concrete can be worked into place
easily when the mix has enough sand
in it. Where the concrete is placed
sloppy, the finishers are always delayed
and more time is required to work out
the high and low spots left when the

excess water gets away.

Speeding Up Work

O speed up the job, we waited until

two sections of the base course were
filled, leveled and tamped before we put
on the black-colored topping. We struck
off the topping, wood-floated it and then
steel-troweled it sparingly. Finish trow-
eling was not needed since the court was
to have a mat- or canvas-like finish. To
get this finish we brushed the top both
ways with a long-handled floor brush
just as the water sheen disappeared from
the surface. The brush had hair bris-
tles. I found that if a brush is used
too soon, the surface smears over; if
too late, the brush will not score the
surface. The right time to do this brush-
ing, we found, was just when we wanted
to go to dinner or go home at night,
but we always stayed to complete th
job.

Curing Important

E have found that it pays to cure

concrete carefully, especially on
high grade colored jobs or surfaces which
will receive a lot of wear. As quickly
as the surface was hard enough so it
wouldn’t mar, we covered the finished
sections with heavy waterproof paper to
keep the concrete from drying out. After
the last slab had cured for four days,
we took off the paper covering and
cleaned and washed the court with clear