http://www.geocities.com/richtoybox/pondintro.html
Zone 7A/B Virginia
"Chip" wrote in message ...
RichToyBox wrote:
Concrete, whether truck mixed or gunnite/shotcrete is made of Portland
Cement, sand, water, coarse aggregate (gravel or crushed stone) and
admixtures. The sand, water and coarse aggregates should not pose any
problems. Most of the admixtures are used in such small quantities and
are bound in the concrete, so I don't see a problem with them, either.
You seem quite knowledgeable about concrete, so if you'll allow me I have
a couple of questions.

I have a plastered Shotcrete diving pool built in '87. Planning to
convert it to a swimming pond with fish. Plan to raise the 8.5' deep end
to 4' with dirt overpoured with concrete.

1) Do I need to take off the plaster around the sides, so the new concrete
floor edges mate with the old Shotcrete?

2) Will I need to tie in the floor re-bar to the old wall's re-bar or even
use re-bar in the new floor at all.

3) For fish, do I need to coat the old plaster and new concrete floor with
Epoxy or will normal pool paint do?

Chip

I would use a good clean sand or gravel for the fill. Dirt settles, even if
compacted fairly well. If you use sand, fill the sanded bottom with water
to a height above the sand to break the water tension that allows us to make
sand castles, and the sand should become very well compacted.

I would remove the plaster from the sides and slightly roughen the concrete,
then use an acrylic bonding agent to get the concrete to bond as well as
possible. The sloped bottom will need more concrete removed where the new
floor ties into the old floor, since the minimum thickness of concrete
should be 2 of the concrete rock thicknesses and 3 is better.

The reinforcement is needed to prevent what would be called temperature
cracks from being large. All concrete shrinks. With low water to cement
ratios and continuous moist curing, the shrinkage is reduced. This
reduction in shrinkage may be sufficient to prevent any cracking, and the
use of rebar will distribute the shrinkage tension throughout the concrete
to further reduce chances of cracks. The rebar does need to be tied into
the walls and floor, though not tied to the existing steel. Drill holes
into the existing concrete to obtain bond. I would drill the holes at
different angles giving a chinese handcuff type friction, rather than making
them parallel to each other. The reinforcement of the floor could be done
with wire mesh reinforcement.

Slab thickness should be 6 to 8 inches thick. A proper bottom drain with 4"
pipe should be installed prior to concrete, so pipe friction will be
minimized from bottom drain to pump.

As for a coating, the ones that I am seeing used on other pond construction
are rubberized urethane type mixtures, similar to the spray on truck bed
liners. I wouldn't think an epoxy would be needed, except as a crack repair
material. The regular pool paint should be designed to work with concrete
and would be adequate.
--
RichToyBox