contractor overdue

[kurt]

It's beautiful, and it's funny because that mess has probably been working just fine for several decades.

[mjr6550]

What do you think of fiber mesh instead of wire mesh?

Both are to minimize shrinkage cracking. I have not experience with fibers. I think some contractors complain about finishing it, but it is a garage. I have never seen WWF installed properly. Its supposed to be properly supported and in the top 2 inches of the slab. Supporting it in the correct position and keeping it there while you walk on it is not easy. Just about every contractor lays it on the ground then pulls it up into the concrete with a piece of bent rebar (while standing on it). That does not work.

There was a good article on slabs (maybe even garage slabs) in JLC a year or two (or three?) ago. I believe they recommended #3 or #4 rebar at 2' o.c. I think that is how I would go.

You could also forget all of the about and just put some control joints in the slab and let it crack there. If the base if good the slab will be fine.

[David Meiland]

My best slabs have been done with #3 bars on a 12" grid, 6-sack concrete batched for a 3" slump with water reducer added so we can move it into place, and fiber added also. Put the bars on dobies, and put a 4' length of bar diagonally a few inches from any inside corner or you'll get a radiating crack. The whirlybird will burn the fibers right off, they are a non-issue for finishing in my experience although you may find an occasional clump. For control joints I usually use a product called Combi-form, which doubles as a screed rail during the pour. I get to spend other people's money doing this.

Pouring inside a building is a PITA. When a slab is outside, you can start working the edges all the way around and then get on it. When it's inside, you may want more guys. If you're doing it this time of year in a cold climate, you may end up waiting for it to become finish-able. I have power-troweled at 3 AM with a helper holding a work light after waiting 12+ hours.

[Chad Fabry]

John, you're placing eleven, maybe twelve yards of concrete. Upgrade to a 4500# or 5000# mix with one's and two's. Order it with a 3-4 slump, wet it on site enough to get it placed. Maybe a 5 or 5-1/2. Since you're not placing at a four because your contractor doesn't have enough help or skill, add the fiber for 6 bucks a yard. Order the micro fiber. It's stronger and less 'hairy'. Upgrading the mix to 4500# or 5000# buys some grace for placing the product too wet and it makes awesome cream in the steel troweling stages. The upgrades will add less than $200. Ask for the load data sheet if you let your contractor place the order.

Edit: just read Dave's post. It's good advice too.

[John Dirks Jr]

Highs in the upper 40's on the scheduled day of the pour.

[Chad Fabry]

Highs in the upper 40's on the scheduled day of the pour.

Do not add water reducers at those temps- you'll be waiting for days to trowel.

[John Dirks Jr]

Expirrence contractor taking care of all this. He did mention a higher psi mix. That I remember. And fiber mesh.

[kurt]

Two really good posts from Dave and Chad about the realities of placing concrete......

[John Dirks Jr]

13 yards went in today. They did have to wait several hours before final trowel. Zip Strips were installed every 12' in both directions as control joints. The interior is hand troweled smooth and the entry apron is broom finished with a control joint at each post. Some rain is passing through so I covered the exposed apron.

I asked them how long before I can park on it. They said 1 week. Does that sound like enough time? Temps are struggling to reach 40 degrees over the next week or so.

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[Marc]

Let me know when the house warming party is.

Marc

[John Dirks Jr]

Let me know when the house warming party is.

Marc

It was scheduled for 3 months ago.

[John Dirks Jr]

Maybe the high humidity from the rain will slow the water evaporation from the mix and aid the curing in these less than optimal air temperatures. I can only hope at this point.

[Jim Katen]

Maybe the high humidity from the rain will slow the water evaporation from the mix and aid the curing in these less than optimal air temperatures. I can only hope at this point.

Rent some concrete blankets and cover it up for a few days.

[John Dirks Jr]

Maybe the high humidity from the rain will slow the water evaporation from the mix and aid the curing in these less than optimal air temperatures. I can only hope at this point.

Rent some concrete blankets and cover it up for a few days.

How about I get some 4 mil plastic. Will that work?

[John Dirks Jr]

Maybe the high humidity from the rain will slow the water evaporation from the mix and aid the curing in these less than optimal air temperatures. I can only hope at this point.

Rent some concrete blankets and cover it up for a few days.

How about I get some 4 mil plastic. Will that work?

Even then, I wouldn't be able to get it done til this eve. In that case, would it be too late for such effort?

[kurt]

I wouldn't worry about it.

[John Dirks Jr]

I wouldn't worry about it.

Thanks. They had hot water in the mix off the truck. It was pretty solid this morning when I knocked on it with my knuckles. It didn't gouge when I picked at it with my finger nails.

[Jim Katen]

How about I get some 4 mil plastic. Will that work?

Even then, I wouldn't be able to get it done til this eve. In that case, would it be too late for such effort?

In terms of damage from cold weather, it won't make any difference at this point. Between the hot water and the heat of hydration, it'll be fine.

In terms of a gentle cure, it might still help to soak the surface and put some blankets or plastic on it. You don't want the top drying out too fast.

[kurt]

Yes. I'd be doing the usual hose and visqueen cure, but even that's probably not necessary.

It'll be fine.

[John Dirks Jr]

Great! I just leave it be. But it is interesting to learn details about curing.

Thanks to everyone for their opinions.

[kurt]

Posts #28 & 29 (Meiland/Fabry) are probably the best condensed tutorial on placing concrete I've read anywhere.

If there's a next time, pay attention to the principles outlined in those posts.

[John Dirks Jr]

Posts #28 & 29 (Meiland/Fabry) are probably the best condensed tutorial on placing concrete I've read anywhere.

If there's a next time, pay attention to the principles outlined in those posts.

Yes, I surely do appreciate that information From David and Chad. In my case, by the time I began this discussion about the pending concrete pour, the wheels were in motion. I chose to place trust in the contractor. I've been satisfied with the quality of their work. It's been the delays that pushed me to the edge.

Vehicle doors are all that's left to do as far as contract obligations. That is supposed to be done next week. I'm eager to pay when contract is fully satisfied.

Thanks again everyone.

[mjr6550]

Great! I just leave it be. But it is interesting to learn details about curing.

Thanks to everyone for their opinions.

Probably too late to do anything at this point. Moist curing is usually a good idea, but I'm not sure about that if temperatures could drop below freezing. The link below has some good info on curing.

http://www.lmcc.com/concrete_news/0110/ ... lments.asp

[John Dirks Jr]

The door installer did a really nice job. The receptacle I installed for the openers doesn't reach so all I have left to do is fix that. Extension cords are powering them now. [:-bigeyes

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[Marc]

The door installer did a really nice job. The receptacle I installed for the openers doesn't reach so all I have left to do is fix that. Extension cords are powering them now. [:-bigeyes

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Never noticed until now but are you using the siding to brace the walls?

Marc