Concrete question for the TBH braintrust

[BOHTR]

My only experience working with concrete thus far is concreteing posts in the ground. Tomorrow, I'm pouring a 16" x 16" x 16" block at the base of my flagpole. How long should I wait to pull the forms so I can round off the corners with the edge tool ? It'll be 100 degrees, at least, when I fill the forms. Also, any ideas on how many 80 lb. bags I'll need ?

[Mike]

As far as the amount, I would get 4 of the 80# bags and you will have a bit left over if you are using Quikrete or Sakrete brand. Each bag is 1152 cubic inches and you need 4096 cubic inches to fill your form. If you go with Maximizer, you will need only three, The Maximizer might give you a smoother finish due to the lightweight aggregate.

As far as pulling the forms off, that is a guess because it is 16" deep. It also depends on the amount of water you use. Remember, if you can pour it out of a wheelbarrow, it is too wet and you need more time.

I would wait an hour or two and see what happens.

[MountainMan]

Best way to do the forms is to cover the concrete with plastic and wait about 24 hours. By then it will set and you can punch the forms off with a sledge hammer without risking the concrete running or cracking. The more water you use, the longer it'll be. If you want to round the corners, I would suggest using something round to begin with such as steel edging or half a a carboard tube. Trying to round it off without the concrete running will be a challange....

I agree with the 4 bags of Quikrete. Mix it in a bucket or wheelbarrow and pour.

Hope that helps.

[Tmag]

They started knocking mine off in a couple hours.

[Bill]

Are you planning to put some rebar inside the block?

[Txag96]

Concrete will dry at varying speeds based on several factors. Wind, direct sun, amount of water you use in the mix, ambient air temperature, and the type of mix. All that being said, if you want to "round off the corners" it would be ideal to start with a circle to begin with. If you start with a square, then you you need to wait until the top is just firm enough to trowel, but not so hard that it will chip. I wish I could help you more, but it is really not something that you can just tell someone.
By the way the hotter, the more wind, the more direct sun, and the less amount of water you use are all things that will make it dry alot faster.

[sacs]

with this heat i would pay someone to do it for me.

[bearintex]

Get you a stick of molding that has a contour you like. Nail it to the top of your form on the inside. Fill 'er up and get 'er done!

[Mike Murphey]

In this heat I would put some plastic over it and wait 24 hours......maybe even some wet burlap sacks to slow the initial curing down.....You want this to last and not crack in a few years.....knock off the forms the next day, but run a side trowel around the corners after you pour the concrete, maybe 3-4 hours..this will make the top of the concrete more eye appealing....Be careful on rebar..needs to be the correct size or it can cause cracking.....I would suggest wire mesh to add strength....remember for concrete to fully cure it will take ~30 days.....good luck and don't get too hot...

[Hillary]

Lay the top with wet sacks, cover it in plastic, or flood it.... especially with this heat...

Even better, wake up at 5 or 6 and pour it.... you can't imagine the difference it makes in the heat of the concrete...

But you aren't dealing with a massive pour, I wouldn't worry about waiting 24 hours, unless it is out of convenience to you. If you pour in the morning, wait until late afternoon and you should be fine... but that concrete will be fine in the forms too.

Grease them and they will come right off.

[Dale Moser]

I believe I'd simplify the deal and get one of those cardboard type forms at the Home Repot and pour it round. You can round that edge with the form on it too.

[cosmiccowboy]

That's what an edge trowel is for. You round off the edge while the form is still on.

[GWHunter]

Cosmic said it best, and as hott as it's gonna be Id say by mid afternoon the forms can come off!

[Tmag]

Even better, wake up at 5 or 6 and pour it.... you can't imagine the difference it makes in the heat of the concrete...

Starting a little late eh? We start around 1-2am this time of year and the boys are headed home when the heat hits at 2-3pm.

[HandiKap Bowhunter]

Starting a little late eh? We start around 1-2am this time of year and the boys are headed home when the heat hits at 2-3pm.

x2 I have had my placements ranging from 130 to 330 depending on the size for the last 3 weeks. Sucks but atleast Im home before the heat gets to terrible!!!