Pouring floor today-nervous/need advice

[bigred292]

Finally getting to pour my floor today- been waiting since November.
24x32 with radiant heat. Everything is good to go, have a 4 inch pitch and will have a drain at the apron.
My question is this: I plan on doing epoxy floor- I'm under the idea that a light broom finish would be best because it will grab better. Is this true?
Concrete is 3500 w/peastone and fibermesh.
The concrete is supposed to be here at 2.
Any help would be appeciated.

Also forgot, looking for info on curing process. Next few days calling for 75 degrees. Advantages/info on wet curing would be helpful.
And lastly, how long to wait to apply epoxy.
Thanks in advance!

 

[rugerlady]

Hi Bigred,
A light broom finish is good if you are using a 100% solids epoxy. Normally the concrete must cure for 30 days before applying a coating.

 

[bigred292]

Thanks for your help- You said it would be good, but which is better- I can do either way

 

[Steves32]

Make sure you either tool in some expansion joints or saw them the day after the pour.
Also- visqueen is highly recommended!

I was told by several epoxy suppliers that a broom finish isn't enough. The cream rises to the top when they work the slab w/ trowels & you need to either grind or acid wash to open it up & get a good bond.

Test the concrete after 30 days the high tech way. Tape a piece of plastic down to slab so edges are sealed & remove after 12 hours. If it's dry, you are good to go.

 

[ConCretin]

Also forgot, looking for info on curing process. Next few days calling for 75 degrees. Advantages/info on wet curing would be helpful.

Good advice by others, especially control joints.

Your goal is to keep the concrete in a continually moist condition for at least seven days. Easiest way is to wet it down and cover it with poly. re-wet as necessary.

Don't just wet it down every once in a while and let it dry out in between.

 

[rugerlady]

Let me re-phrase that then, light broom finish is "ideal" ! Let me know if I can help with anything else.

 

[bigred292]

It's just after 5, floor guys left about 45 min ago. Everything went great, much to my suprise.
I was going to put down a light broom finish - talked to the guy and explained what I was going to do(epoxy).
He told me tbe best way was to do a bull float finish-no whirlybird. He told me tomorrow I should go get a "white" brick and smooth down any visible lines, just like you would do to drywall. After smoothing out lines keep floor wet with a mist for about 3 days.
I kinda went with the guys judgement- he knew alot about epoxy and also mentioned that it needs to be etched.
Hopefully I made the right choice. Radiant heat came through fine, held 25 psi throughout the pour.
Thanks for all the help- anybody think of anything else I should do please let me know.

 

[ConCretin]

just got home a re-read the thread. Noticed that you have radiant. Unless you are absolutely positive your tubing is anchored, saw cut control joints are out. If your finisher didn't groove the floor, you should just deal with any random cracks before you apply your floor.

I hope you end up satisfied with the advice you got from your finisher. My concern is that bull floating is the first of several steps required to get a flat floor. Floating with a power trowel would definitely have helped. It may take more than knocking down the ridges with a brick. Sorry to be negative on such a big day but I think your floor guy may have taken the easy way out.

 

[Edger]

Make sure you either tool in some expansion joints or saw them the day after the pour.
Also- visqueen is highly recommended!

I was told by several epoxy suppliers that a broom finish isn't enough. The cream rises to the top when they work the slab w/ trowels & you need to either grind or acid wash to open it up & get a good bond.

Test the concrete after 30 days the high tech way. Tape a piece of plastic down to slab so edges are sealed & remove after 12 hours. If it's dry, you are good to go.

Steves32 is right, it has to be etched or prepared in some way before epoxy coating. Even with a bull float finish the cream (laitence) is too sealed to be sure the epoxy will adhere. The flatter the finish, the better the epoxy finish. 28 days is standard for allowing concrete to cure. Apparently it lets out gasses and stuff while it is curing.

 

[dd564]

Steves32 is right, it has to be etched or prepared in some way before epoxy coating. Even with a bull float finish the cream (laitence) is too sealed to be sure the epoxy will adhere. The flatter the finish, the better the epoxy finish. 28 days is standard for allowing concrete to cure. Apparently it lets out gasses and stuff while it is curing.

This is why the light broom finish would have been optimal.

 

[Edger]

This is why the light broom finish would have been optimal.

It has been said before on these forums and I would like to say it again that no finish of the concrete is suitable for coating, it has to be prepared by etching, or grinding etc.

The smoother the finish, the better the coating looks and the stronger the coating because there are no thin parts on high peaks. I am not saying you should have a highly polished floor from too much floating, but the smoother the better (and even then it will have some float ridges).

This argument has been going on since coatings for concrete were invented, but a profile of the surface I believe is detrimental to the coating integrity.

If you put down a good coating then that is what protects the floor and provides the finish, any finish under the coating does not add to the quality.

 

[ConCretin]

It has been said before on these forums and I would like to say it again that no finish of the concrete is suitable for coating, it has to be prepared by etching, or grinding etc.

I'll defer to you guys on the most desirable finish profile because I'm not an expert on epoxy but i do think a flat floor is important.

The OP's floor guy was presumably paid to provide a finished product. He convinced the OP to accept a bull float finish, which probably cut his cost in half. If it were my floor, I would have asked them to float the slab with a power trowel, knock it down and finish it with a fresno. At this point you could do a light broom finish or just leave it as is. This would have provided a flat floor, with minimal ridges.

Seems to me this would be a good surface for etching and epoxy. Too late in this case but maybe good advice for the next time.

 

[darkk]

I don't know about the epoxy coating part. But I do know that you need to keep the concrete wet for a while. It was 90+ deg when I did mine in Ct. I bought a side to side fan sprinkler that would cover 50x40 spray. I hosed the concrete all that day with a hand sprayer, really soaked it that night about 10 pm. In the morning I went to the middle of the slab and set up the sprinkler. I let it stay very very wet for 7 full days. Some companies flood (keep it under water) the concrete on large jobs. my slab was only 30x30. It's been two years now and not so much as a hairline crack. I have no relief lines cut in it either.I used 3500PSI with 6" square mesh and the fiber mesh additive.The premise is to allow the concrete to stay wet all over until the moisture works it's way from the inside out. If not kept wet it will dry to fast on the outside while the inside is still uncured causing premature cracking. Google concrete curing process.

 

[ConCretin]

The premise is to allow the concrete to stay wet all over until the moisture works it's way from the inside out. If not kept wet it will dry to fast on the outside while the inside is still uncured causing premature cracking. Google concrete curing process.

You definitely did it right but to clarify; the purpose of curing is to prevent premature drying and ensure there is adequate mix water to allow the hydration process to develop the full design strength.

Proper curing is about compressive and tensile strength, which helps with crack control but is mostly about durability. The lack of cracking in your slab is probably the result of your decision to use welded wire fabric and fibermesh, which was a good one.

 

[bigred292]

OP here- thanks for all the replies.
I have been keeping the floor wet as much as possible. Last night after work I used a white brick to knock down any ridges left from the bull floating.
I'm in New England so the weather has been cosistently 70's since floor was poured.
Here's my next question that someone just hit on. The guy is supposed to come tomorrow (Sat) to make cuts in the floor. I too used welded wire mesh as well as fiberglass in cement. Should I still do cuts?
As far as the floor I was working on it til midnight to get it to my liking. Overall I'm happy with the floor and finish- I've seen some that are better but have seen some that are ALOT worse. I think once I put epoxy down it'll be sweet.
I also thought the bull float finish would give the floor itself a bit of a rough surface as far as being too slippery or slick with the epoxy- friend has a beautiful floor but sometimes it's as slippery as a hockey rink.
Just my thoughts.

 

[darkk]

Eveyone I talked to was 50/50 on the cut lines. They said ALL concrete cracks. I opted not to and chance not cutting mine. I just couldn't find a spot where I could live with the cuts. I hope it was a wise decision...

 

[ConCretin]

Here's my next question that someone just hit on. The guy is supposed to come tomorrow (Sat) to make cuts in the floor. I too used welded wire mesh as well as fiberglass in cement. Should I still do cuts?

Unless you planned ahead with laying out and securing your radiant heat tubing, I'd be reluctant to saw cut the floor.

If you have properly supported wire mesh and fibermesh I'd roll the dice on random cracks. If you haven't seen them yet, you may not get any.

 

[Cryptic1911]

I'd skip the cuts if you have radiant tubing in the floor. Don't want to cut through all your tubing.. only get one shot

 

[Steves32]

You need control joints.
My friends slab was 35x45, he put 1/2" rebar in on 18" centers & 6" 3000 psi & opted for no control joints. Within a year- he had several random cracks.
Mine is smaller at 20x21, mine is 8" thick 3500 psi, 1/2 rebar on 18" center w/ visqueen & sand, a monolithic pour & I had them tool in control joints in 7' squares. It's been 6 weeks now & in the bottom of all the tooled joints are thin cracks- none in the field.

 

[rugerlady]

I'm going to go one step further with the floor prep. All concrete needs to be profiled before applying an epoxy. This can be done by chemical (acid wash) or mechanical (diamond grinder) means.
Another thing about fiberglass reinforced concrete. After the floor has been profiled, you must take a small torch and burn off any fibers sticking up. If these are not burned off, you will have very sharp epoxy coated fibers sticking up from the concrete.

 

[bigred292]

On installation I tied the tubing to the wire mesh, which was placed directly on the dow board insulation. I was planning on doing a 1/2 inch deep cut- that leaves plenty of room for error. I was there for the pour and made sure they didn't pull up the mesh. Floor thickness goes from 5 1/2 inches to 4 inches in spots- plenty of room to cut in my opinion.
Floor is 24 wide by 32 deep. Mason's recommendation was to put 2 cuts front to back then 3 cuts side to side, which would leave me with 12 squares..........is that overkill-seems like alot of cuts.
Thanks Christine for the tip on the fibers-would never have thought of that!

 

[ConCretin]

Control joints are certainly advisable in most cases. Your floor is still cracked but the cracks are nice and straight. As long as you are 100% certain your tubing didn't float up, go ahead and cut.

To provide a reasonable certainty that the floor will crack at the saw cut, the standard depth is thickness/4 so for a 4" slab, you should cut 1" deep. The best time to cut is right after placement if you have an early cut saw or within 24 hours if you don't.

On a 24x32, I would make one cut longitudinally and three across. That will give you panels of approx. 12'x10', which should be fine.

 

[jumbo61]

Control joints are certainly advisable in most cases. Your floor is still cracked but the cracks are nice and straight. As long as you are 100% certain your tubing didn't float up, go ahead and cut.

To provide a reasonable certainty that the floor will crack at the saw cut, the standard depth is thickness/4 so for a 4" slab, you should cut 1" deep. The best time to cut is right after placement if you have an early cut saw or within 24 hours if you don't.

On a 24x32, I would make one cut longitudinally and three across. That will give you panels of approx. 12'x10', which should be fine.

Why wouldn't 2 cuts across work. Dividing the slab into thirds? ~@10'.

 

[bigred292]

Cuts done today- no problems.
Went about 1 inch deep- wound up making 1 cut front to back and 2 cuts side to side.
Gotta admit I was tense when the saw was going full blast, just kept a nervous eye on the pressure gauge at the heat manifold.
Now I can sit back and wait the 30 days to lay down the epoxy- might wait a little longer because that will put me in the dog days of summer.
Thanks for all the advice everyone!

 

[ConCretin]

Why wouldn't 2 cuts across work. Dividing the slab into thirds? ~@10'.

Looks like you AND the OP figured out my math skills are apparently lacking.

Thanks for the correction. Congrats bigred292!