Colunms (curing time)?

[r136dg]

My contractor tells me his concrete crew will pour columns tomorrow afternoon. Friday they will set the per-fabricated floor. That means they"ll have to strip the braces from the columns Friday morning, possibly/probably the forms also. To me that (16 hours or so) seems way to early to be stripping and than handling prefabbed concrete around these columns that are still very green. Should I be concerned here? What it's looking like to me is they want to get to the next $ installment. 

Thanks in advance!

[Strange]

Built and been involved with a couple houses here. 

 

Pour the columns one day, start removing the forms the next morning. Even in the states we did the same thing. Pour today, strip tomorrow, unless its a VERY thick pour, like 3-4-5 foot thick. 

 

You are surely to get people getting all technical telling you your house will fall down if you don't wait 3 days 12 hours and 23 minutes. 

 

That concrete will be hard in a couple hours, and in 16-20 hours at about 20 cm thick it will be plenty hard and probably hot to the touch as well. At this point in your build its not load bearing, but needs to stay moist, so your guys should have wet burlap wrapping on the columns or at least have a guy with a hose spraying it every hour or 2. 

 

Again, its not load bearing right now, so no problem. Even if they bump the columns with the prefab concrete panels it will be fine. 

[r136dg]

24 minutes ago, Strange said:

Built and been involved with a couple houses here. 

 

Pour the columns one day, start removing the forms the next morning. Even in the states we did the same thing. Pour today, strip tomorrow, unless its a VERY thick pour, like 3-4-5 foot thick. 

 

You are surely to get people getting all technical telling you your house will fall down if you don't wait 3 days 12 hours and 23 minutes. 

 

That concrete will be hard in a couple hours, and in 16-20 hours at about 20 cm thick it will be plenty hard and probably hot to the touch as well. At this point in your build its not load bearing, but needs to stay moist, so your guys should have wet burlap wrapping on the columns or at least have a guy with a hose spraying it every hour or 2. 

 

Again, its not load bearing right now, so no problem. Even if they bump the columns with the prefab concrete panels it will be fine. 

Thanks Strange,

No worries on load bearing, but I am having a hard time getting around those green columns getting any vertical stress from the sides. Just seems 20 cm straight up for 3 meters could get stress cracks from a accidental shoulder blow in that short of time.

I have no experience with these columns but from the experience I do have with crete, this just doesn't sit well with me. Especially with the crap mixes they seem to be using. Supposed to be c-pac 240 which I think is the standard footing mix here. I'll go out there tomorrow & check the redimix drivers ticket and just try to roll with it. I'll also make sure that wet cure is put in place.

Thanks again!

[Strange]

52 minutes ago, r136dg said:

Just seems 20 cm straight up for 3 meters could get stress cracks from a accidental shoulder blow in that short of time.

 

Shoulder blow? No way. I clipped one the edge of a tractor blade at the base and that cracked it but stopped the tractor dead too. That was probably 24 hours after pour, and that was hand-mix in one of those black bucket things. 

 

C-pac is fine, 240 is fine, but they like to make it too wet so its easy. Wont fall down. 

 

End of the day, its your money and your house. Form it up, pour it, and get them to find something else productive to do for 1 day, then pull it all off the next. Or they can have a beer day. They probably won't like it, but its your stuff. Be polite but firm. 

 

Its all entirely up to you. 

 

[eyecatcher]

Give me one good reason why you would want to strip shutters the next day?

 

The only reason here is the tight Thai builders renting shutters at 12bt a column are going to save 300bt by getting them returned tomorrow instead of at the weekend.

 

I insisted mine stayed on for a week, and yes I am a technic al guy but the shutters are doing a better job than wrapping in polythene  to help the connie cure better.

they are also protecting them from damage, especally the corners which are green and likely to expose the rebar.... and of course rapid drying out in this weather with induces shrinkage and of course cracking.

 

Theres no problem with the loadbearing strength, yes after 3 days its about 70% to full strength in compression but unless you are watering regularly and wrapping which doesn't happen here when builders arrive at mid day then if its no detriment leave them on until they need to re sue them on the upper floor.

sorry but next day stripping is a no no wherever you are in the world. its just bad practice.

[eyecatcher]

Your concrete will only be 180/220/240 stang if you get your concrete cubed and crushed; otherwise its what he said, she said. who knows.

 

It doesn't matter what is being delivered because if they add more water(which they alwaysdo) it weakens it immediately.

 

More water means voids around the stones are being filled with water instead of sand and cement so of course when that water dries out what do you have ? voids; and voids means holes/weakness.

 

This is the main purpose of immediate wrapping  to prevent rapid evaporation of the water and induced cracks.

 

But if the water is in there it going to come out whether its wrapped or not.

 

Rule of thumb: more water makes it weaker so more sand; more cement; now more expensive