I'm going to be making some large square planters out of concrete. Basically
3x3x3, with sides about 3" thick. I'd like the finish to be as smooth as
possible.

What kind of concrete/cement should I use? Can I just run to the
Lowes/Menards/Depot and pick up some quickcrete?

Sorry for the cross post. I wasn't sure where this subject belongs...

Thanks in advance

Tim

"Diezmon" wrote in message
m...
I'm going to be making some large square planters out of concrete.
Basically
3x3x3, with sides about 3" thick. I'd like the finish to be as smooth as
possible.

What kind of concrete/cement should I use? Can I just run to the
Lowes/Menards/Depot and pick up some quickcrete?

Sorry for the cross post. I wasn't sure where this subject belongs...

Thanks in advance

Tim



If you want smooth, don't use concrete. the pebbles in the aggregate will
show on the surface of the mold. Only on surfaces you can float will it
appear smooth.

I suggest you either use ordinary Masons Mortar or Sand Mix. Both of these
have no pebbles and will harden just like concrete but with a more uniform
appearance. Both are similar, I think the grade of sand inside makes the
primary difference (possibly the ratio od portland to sand as well) the
quickcrete website has some info.

For a planter, often people will mix polystyrene (little balls inside a bean
bag chair) AKA Styrofoam is as an aggrigate to make it much lighter. The
foam takes the place of the pebbles. You may have to experiment with
mixtures of polystyrene, portland cement and sand to get a look you like.

I have also seen people sponge on a slurry of almost pure portland cement
onto the surface to fill in any pits and smooth the appearance after
removing from the mold.

Finally make sure the mold is smooth and coated with some kind of mold
release so that it in and of itself does not mess up the appearance.

PipeDown wrote:
If you want smooth, don't use concrete. the pebbles in the aggregate
will show on the surface of the mold. Only on surfaces you can float
will it appear smooth.

Not if you build a mold. I've built dozens of pads up to 3' high for
air conditioning condensers using 5/8" plywood and the sides come out
almost perfectly smooth.

yup , build the outside wall of mold with sanded ply , shellac to
waterproof and smooth , used motor oil as a release agent and normal
quick crete to pour, use a slightly wet mix .

Be aware that concrete weighs in at close to 100 lbs per cubic foot so
you will need to reinforce your molds.

Pound the mold while filling to help remove air bubbles.

Wire mesh in the mold will help keep the sides from cracking.

Good luck with it.

I'm going to be making some large square planters out of concrete. Basically
3x3x3, with sides about 3" thick. I'd like the finish to be as smooth as
possible.


I agree with a light weight approach for this type of container.

INGREDIENTS NEEDED:

Horticultural perlite
Peat moss
Portland cement


Well, it depends on why you want big-ass concrete planters.
If you're trying to stop drunk drivers hurtling off the corner
before they plow into your livingroom, skip the pearlite.

(or car bombers, or whatever. note that a 3' high planter
isn't big enough to stop a tank.... :-) )

I was thinking I'd build the mold with 3/4" ply, then line the inside with
Masonite so it's mucho smooth. waddya think?

Any other "cleaner" release agents I could use?


wrote in message
ps.com...
yup , build the outside wall of mold with sanded ply , shellac to
waterproof and smooth , used motor oil as a release agent and normal
quick crete to pour, use a slightly wet mix .

Be aware that concrete weighs in at close to 100 lbs per cubic foot so
you will need to reinforce your molds.

Pound the mold while filling to help remove air bubbles.

Wire mesh in the mold will help keep the sides from cracking.

Good luck with it.

I agree with a light weight approach for this type of container.

INGREDIENTS NEEDED:

Horticultural perlite
Peat moss
Portland cement
Plastic tub (for mixing ingredients)
Dust Mask or Surgical mask
Gloves
Water
Drop cloth
2 cardboard boxes (one slightly smaller than the other)
Wooden dowels
Chicken wire or Fibermesh
Mason's trowel


Hmm, perlite.. crushed or expanded? (based on what I've read on the web )

where do you find the stuff?

Peat moss. Seriously?

On Fri, 19 May 2006 17:18:14 GMT, "DiezMon"
wrote:

Hmm, perlite.. crushed or expanded? (based on what I've read on the web )

where do you find the stuff?

Bags of it are in a garden center, same stuff used in plants to help
aerate the soil

Peat moss. Seriously?


First link is step by step...nice pictures.

http://www.fogsuwo.ca/trough_project/troughs.html

http://mackeybooks.com/make_a_trough.html



Oren
"My doctor says I have a malformed public-duty gland
and a natural deficiency in moral fiber, and that I am therefore
excused from saving Universes."

DiezMon wrote:
I was thinking I'd build the mold with 3/4" ply, then line the inside
with Masonite so it's mucho smooth. waddya think?

Any other "cleaner" release agents I could use?

I don't use a release agent and have never had a problem. Plain old
sheathing plywood is plenty smooth enough, especially if you are going
to paint the planter. Just use a wet mix and after pouring tamp it down
to eliminate any bubbles as marks recommended. Pound a bit on the side
of the mold, too.

Travis Jordan wrote:

DiezMon wrote:
I was thinking I'd build the mold with 3/4" ply, then line the inside
with Masonite so it's mucho smooth. waddya think?

Any other "cleaner" release agents I could use?

I don't use a release agent and have never had a problem. Plain old
sheathing plywood is plenty smooth enough, especially if you are going
to paint the planter. Just use a wet mix and after pouring tamp it down
to eliminate any bubbles as marks recommended. Pound a bit on the side
of the mold, too.

Possibly that white "tile board" Masonite stuff would leave a good
finish. Also consider rigid foam board insulation and the possibility of
routing decorative features in the foam to cast them into the planter.

Pete C.

On Fri, 19 May 2006 18:10:08 GMT, "Travis Jordan"
wrote:

DiezMon wrote:
I was thinking I'd build the mold with 3/4" ply, then line the inside
with Masonite so it's mucho smooth. waddya think?

Any other "cleaner" release agents I could use?

I don't use a release agent and have never had a problem. Plain old
sheathing plywood is plenty smooth enough, especially if you are going
to paint the planter. Just use a wet mix and after pouring tamp it down
to eliminate any bubbles as marks recommended. Pound a bit on the side
of the mold, too.


For some reason many, many years ago diesel fuel was painted on
plywood with a brush. Supposedly to prevent any sticking of the wood
to the cement. My guess this was the petroleum. What little I form
myself, I whack it with a hammer here and there to settle things
also.


Oren
"My doctor says I have a malformed public-duty gland
and a natural deficiency in moral fiber, and that I am therefore
excused from saving Universes."