Concrete curing in enclosed space

[BigBlue1]

I'm filling a lawn roller with concrete (building my own, actually). Before I cap off the roller tube after filling with concrete I'm wondering how long to leave the concrete cure? The fact that concrete can cure underground - such as in a sonotube or dumping concrete around a fence post - it makes me think it doesn't matter if I seal off the concrete inside quite soon, but the rational part of me says it needs some air circulation to allow evaporation. I'm looking for someone knowledgeable that can offer guidance here. Is it adequate to allow just enough time for any surface water to evaporate and then seal it or should I be waiting longer? I know that curing is a chemical process and not exactly evaporation, but I also know that evaporation does play a part.

Thanks,
Rob

 

[i7win7]

I bought a used 24" by 4' roller at auction cheap because the end plate leaked (rust holes). I set roller on end atop 3 or 4 cement blocks, used angle grinder to cut decent size fill hole. Filled with cement and allowed to cure a couple of days. This thing now weighs over 1 ton. I modified the hitch by attaching an automotive style trailer coupler and a bicycle kickstand. Place trailer ball om mower to back under it. I first used riding lawn mower to pull it. It takes 20+ HP to pull it, if tractor is too small (lightweight) it will push the rear end when you try to turn. After buying a BX2370 Kubota, I bought a 3pt trailer mover to connect to the beast, works great.

Things to consider - HP of your tractor, size of your roller and cement won't go down a 1" fill hole, It's trying to setup after mixing.

 

[bcp]

Concrete cures underwater, so I don't think evaporation matters very much.

Bruce

 

[BigBlue1]

Thanks. I'm already past all that. I have the roller made, out of an ancient steel water softener tank, and I have it filled with concrete. The hole on top was only about 1.5" but I made a funnel from a plastic jug and mixed the concrete at the upper end of the suggested water ratio (not over) and it filled OK with a little agitation from a garden scoop when it stopped flowing. I also have the rest of things well in hand. Just looking for guidance on how long before sealing the tank/roller up.

It's amazing how much more volume your 24" roller has than my 12" one. Mine is around 450#. I have made my roller frame to accommodate JD suitcase weights though so I can add a bunch more weight if needed.


Rob

 

[BigBlue1]

Concrete cures underwater, so I don't think evaporation matters very much.

Bruce

Good to know. That makes sense, since you can dump it in a post hole and then cover with dirt right away. But I just wasn't sure.

Rob

 

[/pine]

I would leave it vented until it no longer feels warm on the outside...

 

[BukitCase]

Me too; just because it's "cured" doesn't mean it won't still outgas. In fact, I wouldn't actually SEAL it at all, just cap it to keep bugs out... Steve

 

[Industrial Toys]

Concrete does not require air to cure. It's an exothermic (sp?) process. A chemical reaction. Cold will really slow it down though.

I bought one of my rollers with crushed stone in there. Plenty heavy enough. And no need to drain water every year.

 

[BigBlue1]

Me too; just because it's "cured" doesn't mean it won't still outgas. In fact, I wouldn't actually SEAL it at all, just cap it to keep bugs out... Steve

I'm not 'sealing' it, per se, but I am welding on the mount to support the flange bearing on the 'fill' side and that will cover the hole mostly. If airflow or circulation was important then it would be quite limited. But it isn't going to build pressure.

It's been in the 40's (F) here and it has been curing for about 48 hours now. It was 'solid' within 12 hours.

Rob

 

[i7win7]

Thanks. I'm already past all that. I have the roller made, out of an ancient steel water softener tank, and I have it filled with concrete. The hole on top was only about 1.5" but I made a funnel from a plastic jug and mixed the concrete at the upper end of the suggested water ratio (not over) and it filled OK with a little agitation from a garden scoop when it stopped flowing. I also have the rest of things well in hand. Just looking for guidance on how long before sealing the tank/roller up.

It's amazing how much more volume your 24" roller has than my 12" one. Mine is around 450#. I have made my roller frame to accommodate JD suitcase weights though so I can add a bunch more weight if needed.


Rob

450# roller, weight of lawn tractor unknown. I think you will have difficulty aligning 3 drawbar holes so it can be pinned on. Using a pair of clevises don't work very well either. Using the automotive style of trailer connection is cheap and much easier to connect even without a 3pt.

 

[Industrial Toys]

Yes, connecting a heavy roller is a PITA. It can also push over a small tractor if you are going down hill and turn too soon, fast or sharp. Ask me how I know?

 

[BigBlue1]

450# roller, weight of lawn tractor unknown. I think you will have difficulty aligning 3 drawbar holes so it can be pinned on. Using a pair of clevises don't work very well either. Using the automotive style of trailer connection is cheap and much easier to connect even without a 3pt.

It rolls. No problems getting it into place!

I may have to mod the hitch to give a little more up/down swing but it fared well on its maiden voyage.

Rob

 

[BigBlue1]

Yes, connecting a heavy roller is a PITA. It can also push over a small tractor if you are going down hill and turn too soon, fast or sharp. Ask me how I know?

I'm pulling it with a Deere x758. I think it can keep 450-800# in check. I have no significant hills.

Rob

 

[chim]

We built this one at work using 24" Sch 40 steel pipe. Each section has a stub piece of 3" pipe that's a bit longer than the width of the section so the sections don't rub each other. It has 4 sections at 12" and the center section is 19". Each one has spokes made of rebar that kept the 3" axle in place while pouring. I had it made in sections so it would make sharper turns without scrubbing.

 

[Industrial Toys]

Oooops!

 

[oosik]

Darn IT - that's not even a tiny bit funny IT. Only somebodies pride got hurt - I hope. Years ago I saw a brand new chunk of corrugated highway culvert. Must have been the excess that was cut off a large piece. It was 48" x about 6' or 7'. While I was contemplating this situation - a private contractor came by and picked it up. Darn........

 

[Cord]

Ok, this is a late post, but maybe somebody will find it to useful. So long as excessive water isn稚 used to thin the concrete, all of the water will be consumed by the reaction. Water evaporating off the surface of a slab will result in problems such as crazing and slab curl. The use of curing techniques and compounds can slow the evaporation and the resulting issues. In your sealed drum, this won稚 be an issue because the water won稚 be able to evaporate. To get the concrete to flow you may be tempted to add more water. This will result in free water, more water than what is needed for the reaction. This free water will form small droplets that will remain as the concrete cures. As this water evaporates void pockets will remain and these will negatively affect the concrete strength. Of course, strength isn稚 critical to your application, the pockets also affect the concrete density.

 

[rScotty]

It will cure without evaporation...in fact it will cure stronger if the surface is kept damp to wet for the first week. You'll see begin to harden within a few hours to a few days, but typically takes about 30 days to reach max strength.

 

[BigBlue1]

Ok, this is a late post, but maybe somebody will find it to useful. So long as excessive water isn稚 used to thin the concrete, all of the water will be consumed by the reaction. Water evaporating off the surface of a slab will result in problems such as crazing and slab curl. The use of curing techniques and compounds can slow the evaporation and the resulting issues. In your sealed drum, this won稚 be an issue because the water won稚 be able to evaporate. To get the concrete to flow you may be tempted to add more water. This will result in free water, more water than what is needed for the reaction. This free water will form small droplets that will remain as the concrete cures. As this water evaporates void pockets will remain and these will negatively affect the concrete strength. Of course, strength isn稚 critical to your application, the pockets also affect the concrete density.

I mixed mine at the upper end of the recommended water amount (on the bag: "start with 2 quarts of water per bag and add more if needed, but not more than 3.5 quarts"). As noted, neither the surface nor voids are relevant here. I just need solid weight. The roller is done now so I'm all set. The end has a plate welded over it but there are spaces where the hole is still able to breathe (due to plate not fitting tightly over the domed end).

Appreciate the tips.

Rob