[Jeremy Hillary Boob PhD]

I'm constructing a poured concrete retaining wall and I've completed the footing and am now building forms for the wall. The forms are plywood and I want them to come off easily after the concrete is poured. People around here usually use diesel. However, I'd also like to "fill in" some of the roughness of the plywood, so the finish on the wall is smoother. I was wondering if, say, a cheap latex paint might work as a form release agent. If not, any other suggestions? Thanks.

 

[user1007]

Latex paint is not going to be much of a release agent. There are all kinds of release agents you can put on for concrete form release---even over fillers you have used to even out defects in the form surface. Check to see what your building supply company has availed.

 

[jomama45]

Personally, I'd skip the paint. It could very well end up coming off of the forms & sticking to your walls, creating one more step than necessary.

Diesel is OK, as long as it's mixed about 50/50 with a heavy oil IMO. Otherwise, just about any thin oil will work, including vegetable oil you already have in the kitchen.

If you want a smoother finish you'll probably have to either sand the plywood first, or rub the wall out later.

 

[Bud Cline]

Any depression in the plywood that would require fill would result in a protrusion in the poured wall if not filled in the plywood. (basic)

so...
Why not leave it as-is, go ahead and pour the concrete, and then remove the forms as soon as practical and rub the wall's surface with a rubbing stone while it is still green?

 

[Gary in WA]

Put some 4mill poly on them before assembling or spray them with sugar water mix before pouring. Don't spray anything on the stub steel or re-bar, though. Gives more time to trowel smooth right after stripping.

Gary

 

[Jeremy Hillary Boob PhD]

Put some 4mill poly on them before assembling or spray them with sugar water mix before pouring. Don't spray anything on the stub steel or re-bar, though. Gives more time to trowel smooth right after stripping.

Gary

Plastic sounds like a good solution. And then I could leave the forms on for a couple of weeks to help with the curing. Is there any potential problem with this? Btw, the wall is about 6' high, if that makes a difference. Thanks.

 

[Bud Cline]

Plastic film will transmit any imperfections that may exist in the plywood. The longer you wait to break forms the harder it will be to correct the wall's appearance. If you break the forms ASAP the wall can be uniformly scuffed/rubbed overall for a nice finish. If you wait a couple of weeks the task will change and not for the better. If you think you have to slow the cure of the wall for more strength then bust the forms ASAP, rub the surface, then cover it with plastic for a couple of weeks if you think there is something to be gained by doing so.

 

[rustyjames]

Diesel as a release agent is probably not allowed in all the 50 states.

 

[Gary in WA]

As Bud brought out correctly in post #7. Jeremy, you must have skipped this from my answer "Gives more time to trowel smooth right after stripping." You obviously can't wait more than an hour, depends on weather, ingredients, etc.

Gary

 

[STL B.]

Stop by a concrete contracters yard and offer $10-$15 for a gal. or two for form oil. I think deisel fuel would work fine or you could mix it with kerosene.........I think canola would work fine also, as long as you strip your forms the following day.

As far as smoothing out the surface I'd just plan on skimming the wall with mortar the day you strip. That will fill in all of the "honeycomb" or air that doesnt get vibirated out of the mix, it will give a even color also.

 

[STL B.]

You obviously can't wait more than an hour

I've never seen a wall form striped the same day it was poured much less within hours.

 

[jomama45]

I've never seen a wall form striped the same day it was poured much less within hours.

I've never actually seen it either, although my Dad insists he poured and stripped a basement in the same day many moons ago.........

It's certainly not something I would suggest for a DIY trial though. A curb, maybe, but not a 6' high wall.

 

[Bud Cline]

or air that doesnt get vibirated out of the mix

Oh Lordy! Wish you hadn't brought that up.:no:
A concrete vibrator in the hands of the inexperienced can result in disaster.

Sh-h-h-h-h-h! He'll be fine as-is, no vibrators.

 

[SteelToes]

I've seen forms striped the same day ... but these where some skinny columns in between block wall not a 6' retaining wall.

I think if you strip em down next morning you will still be able to scrape some of the stuff of.

I've seen plastic used in couple occasions...it will leave surface perfectly smooth in the areas where is stretched out but man will it leave a mess if it gets crumpled up or concrete gets behind it.

I've actually spent few weeks fixing a ceiling that was poured with plastic visqueen over the forms (Europe).
I was not there while they where pouring that ceiling but my "guess" would be that they didn't secure the plastic to the plywood and stuff got all crumpled up in between rebar.
You guys wouldn't believe how bad did that ceiling look like.

There are different grades of plywood.. if you are going to use a CDX ply for the forms there is no "oil" or paint on this world that will cover all of those holes.

Use one smooth side plywood ,oil and VIBRATOR and you will achieve some very satisfying results.

Oh Lordy! Wish you hadn't brought that up.:no:
A concrete vibrator in the hands of the inexperienced can result in disaster.

Sh-h-h-h-h-h! He'll be fine as-is, no vibrators.

What is going to happen if he uses a shaft vibrator?

Skim coating over newly poured stuf will work but you are looking at the work that can be avoided now using better plywood.

AC or BX ply its only 20% more than CDX and unless you are doing a mile long retaining wall that is a money well spent.

 

[Bud Cline]

Steel Toes this site has some fairly nifty features for quoting and stuff like that. You should learn to use them. It would make your comments easier to understand.

What is going to happen if he uses a shaft vibrator?

You have never seen wall-forms blow out from the over-use of a vibrator have you? It's not a pretty sight, and it's not easy to clean up. He doesn't need a vibrator necessarily.

 

[SteelToes]

Steel Toes this site has some fairly nifty features for quoting and stuff like that. You should learn to use them. It would make your comments easier to understand.


You have never seen wall-forms blow out from the over-use of a vibrator have you? It's not a pretty sight, and it's not easy to clean up. He doesn't need a vibrator necessarily.

I know Bud but my brain doesn’t always listen to me nor it does things in order :lol:
I spend one of my summer breaks working for the company that was specialized in building weight stations.
I was that new guy assigned to work with concrete vibrator. :furious::furious:

No they don’t need a vibrator, necessarily, but one would definitely help them achieve what they want.

 

[Jeremy Hillary Boob PhD]

As Bud brought out correctly in post #7. Jeremy, you must have skipped this from my answer "Gives more time to trowel smooth right after stripping." You obviously can't wait more than an hour, depends on weather, ingredients, etc.

Gary

I still haven't seen a response regarding this "can't wait more than an hour" comment. It seems kinda daffy to me.

I've used a concrete vibrator before, without incident. I think it's necessary on a wall like this, particularly since the concrete has to be pumped. In any case, I'll have some experienced help for the actual pour---I'm just trying to do a much of the prep as I can by myself.

After further reflection, I think I'll not worry about the smoothness issue, since the visible parts will probably (eventually) get covered with something (although eventually can be a long time...). But, I am intrigued about using plastic inside the forms, since I'd like to keep it damp and cure it properly.

 

[STL B.]

Skim coating over newly poured stuf will work but you are looking at the work that can be avoided now using better plywood.

AC or BX ply its only 20% more than CDX and unless you are doing a mile long retaining wall that is a money well spent.

Good advice.

You have never seen wall-forms blow out from the over-use of a vibrator have you? It's not a pretty sight, and it's not easy to clean up. He doesn't need a vibrator necessarily.

I've had them bow, buckle, moan and groan but I've never a true blow-out, and I've poured some really crappy looking forms built by really crappy carpenters. So I dont think that it would be to hard for a home owner to build forms strong enough to vibrate.

I do believe that any wall poured and not vibrated was not done correctly. It's not a hard tool to learn how to use, I got a 60sec. lesson once as the pre-mix trucks were pulling into the lot. You just drop the dick in the mix and let it fall at it's own pace when it hits bottom or close to it you pull it out at the same rate that it fell......overlap the pattern by 1/3 all the way down the wall.

I was that new guy assigned to work with concrete vibrator. :furious::furious:

What's to gripe about thats one of the best jobs on a large concrete pour. I learned the same way but contractors really really like to have a crew with plenty of experiance climbing around on large walls.........It makes for job security and it feels nice standing up high on the forms watching everyone else dig trenches

 

[STL B.]

I am intrigued about using plastic inside the forms, since I'd like to keep it damp and cure it properly.

Dont do it, as someone else mentioned if it's not perfectly flat against the forms you'll end up with some really ugly puckers/wrinkels on your wall. It will also leave a glass smooth glossy finish, exterior concrete should'nt have that glossy finnish it's not durable.


Edit.....Strip your forms the following day and wet down the wall and tent plastic over wall (not tight to the concrete) if you really want to, but you really dont need to. Burlap is a better choice for keeping concrete moist for a cure.

 

[SteelToes]

Dont do it, as someone else mentioned if it's not perfectly flat against the forms you'll end up with some really ugly puckers/wrinkels on your wall. It will also leave a glass smooth glossy finish, exterior concrete should'nt have that glossy finnish it's not durable.

Agreed.

STL B.

I read what you said about working with the vibrator being a best job on the site but man i still remember pulling that thing back and forth ...standing in concrete almost up to my knees

Seriously. I still remember