Failed concrete question

[RNeumann]

If you used an unlicensed contractor and you paid for the concrete then you are the contractor! You are responsible for the work. That’s the liability you take on when you don’t hire a contractor. Mother Nature got you- not the finisher or the concrete plant.

If your finisher is willing to float it, have him do it. He’s going above and beyond to make it right for you. If you still don’t like it R and R it later.

 

[jrh009]

If you can find it , MG crete is a topping that will work. Will work down to 1/16" of an inch. It comes with an activator, needs to be applied without any sun light on it. You can set up to screed it on for a flat surface. Steel tools need to be constantly cleaned as it will not come off if it sets up on them. The product sets in 20 minutes or so to pretty much full strength.

I used it on a commercial wharf in Parry Sound about 10 years ago to resurface an area 20' in width by 40' in length to repair a spalled surface. Still there today. Good colour blend with the concrete as well.

I know the product is still around, at that time it was distributed by a firm in Hamilton, On. By the way, I doubt the lack of air had anything to do with your issue. Usually that's a result of guys screwing around with the mix design by adding water on site. That is a strength killer. For shop floors I generally do not specify air and generally spec a surface hardener. Hardeners and air are tough to use at the same time.

I am a structural engineer, with 40 yrs of experience . End uses of shops vary a lot, so some design attention needs to be applied case by case.

 

[fried1765]

I had a 40x60 slab poured for a new shop late last year. Apparently a little too late. Anyway, the concrete plant didn稚 use air entrainment because they were told the concrete was going indoors, which was true, just not that day. The concrete was poured and the last section got wet and of course that night it rained, got much colder than predicted and it spalled. Looks horrible. The concrete guy and the plant are pointing fingers, mines pointed at the finisher. The finisher thinks he can overlay it. I have serious doubts. I imagine I値l end up in small claims court before much longer. I don稚 know anyone who痴 had an overlay. For those of you in the know, is an overlay viable or is my contractor just trying to delay the inevitable? I知 really disappointed it痴 going this way, I宋e used the concrete guy several times with top quality work but he sure dropped the ball on this one.

Fifteen years ago I used a two part epoxy product made by Ameron coatings (PPG company?).
They have many different two part epoxy coating products, for both steel and concrete.
I did a badly spalled 50 old sea wall here in Florida.
The wall looks as good today as it did after I applied the product.
For a spalled floor you could probably do a squeegee application, with several coats.
Great stuff....but it ain't cheap!

I would consider adding micro-balloons to the mix, if the spalled pockets are deep.

 

[Deere Dude]

I did a garage on my house and worked it to much and over the course of time I was constantly getting cement dust coming up no matter how much I swept or vacuumed the floor. Finally I waited until the weather was nice I two part epoxied it. It needed two coats but looked very nice and 10 years later was still very nice. No dust.

If there was a spot that is unusable I would replace that, wait for it to dry, like a month or two, the epoxy the whole floor. I think I used Rustoleum epoxy but am not sure.

 

[MickeyDBC]

They added the calcium to heat it and try to make it set faster (it is an accelerant in the curing process) when they realized it was going to freeze. If you pour too wet (what it sounds like they did) the cement portion of the mix can settle down away from the surface giving you a (what we used to call) a farmer concrete surface (a lot of old farmers would cut the mix with sand and even dirt) that is light on cement and heavy on sand and aggregate and not very durable out of either frugality or necessity. Try chipping it down in the worst looking area and if it gets stronger the deeper you go, chip out the top bad layer and do an overpour but use something like 5 or 6000 psi with fiber reinforcement and make sure to coat the old areas with "monkey milk" which looks a lot like Elmer's glue that will greatly help with the bonding. If you do that it should be fine an not ruffle too many feathers. Good luck but it should be fixable.

 

[Jeepnford]

I’ll try to get over there and post pics tomorrow.

 

[/pine]

This brings up a good point for anyone that uses bagged concrete mix from box stores etc...in regions where freeze/thaw weather is prevalent...it is advised to add an air entraining agent to all batches in the mix...
I'm really surprised it was omitted by the ready mix co. even if it was intended for an enclosed pour...!

 

[s219]

I've been pouring footings for a new pole barn over the last few weeks and we've had freezing weather on and off. I protected the footings with layers of insulation and tarps to keep the concrete from freezing and it worked well.

One time I had some extra concrete that I dumped out at the end of the day and it was out in 20F temps unprotected overnight. You can see where the water in the concrete swelled when it froze and it pushed the concrete apart. Pretty powerful to see it happen like that.

 

[fried1765]

They added the calcium to heat it and try to make it set faster (it is an accelerant in the curing process) when they realized it was going to freeze. If you pour too wet (what it sounds like they did) the cement portion of the mix can settle down away from the surface giving you a (what we used to call) a farmer concrete surface (a lot of old farmers would cut the mix with sand and even dirt) that is light on cement and heavy on sand and aggregate and not very durable out of either frugality or necessity. Try chipping it down in the worst looking area and if it gets stronger the deeper you go, chip out the top bad layer and do an overpour but use something like 5 or 6000 psi with fiber reinforcement and make sure to coat the old areas with "monkey milk" which looks a lot like Elmer's glue that will greatly help with the bonding. If you do that it should be fine an not ruffle too many feathers. Good luck but it should be fixable.

"monkey milk" = Concrete Liquid Bonding Agent
Available at HD and Lowes.

 

[Tractor Seabee]

Yes, below freezing. There痴 some scattered pops scattered throughout I can probably live with. The one section is terrible. The plant added calcium, water was added on site, and I think the last load was in the truck too long. I知 30 min from the plant. I don稚 want a total redo, just the one area I壇 like addressed. It痴 right inside one of the overhead doors, I wouldn稚 be able to run a creeper across it. I don稚 live in a metro area, I don稚 know of any contractors that any sort of license other than a local city business license. This is on the family farm in a county with no restrictions. I値l try to get some pictures later.

I have a lot of concrete experience and have been a QC inspector, with many training courses. If the slab froze in spite of the calcium (which nobody but amateurs use anymore) you have potential for structural failure. The plant would not have provided air-entertainment w/o it being in the order. Besides air only protects downstream after the hydration is complete. Your remedy is of a cost beyond the award capability of a small claims court.

It cost twice as much or more to remove the existing which you have a good case for demanding; so, you have that as a lever on the contractor. Yes, the blame is on the contractor. I assume he is a small business guy without any extra resources, under insured, or not insured for errors and omissions. Naturally you did not require a performance bond. You are in a good negotiating position for total replacement. If I was your QC faced with this conundrum; I would advise you: Sandblast the entire surface and remove all dust and loose particles, add a new form on top for a complete new slab same thickness as previous, install reinforcing, and construction joints making sure it is on chairs not being lifted through the concrete, you order the concrete not your finisher (more on that later), do not add water on site that is in excess of the plant mix design, finish, cut control joints (1/3 deep as slab is thick) approx every 12' each way as right then not the next day. Cold weather (below 40 degrees) cover with insulating blankets after spraying curing compound. If you finisher poo poos all this find a new one or convince him to learn your way. Quality concrete work is not el cheapo work especially in cold or hot weather.

Concrete Mix. Discuss with the batch plant mix engineer your situation and get their advice on additives to help prevent freezing, water reducing to help finishing low slump concrete (that is why back water finishers add extra water). If the building will be open for an extended period of future freezing weather the add 4-5% air. 4000 PSI strength is plenty for a slab on grade support by a solid sub-grade (your deficient slab). Strongly consider using synthetic fiber instead of steel reinforcing. Do not waste money on wire mesh unless it is solidly installed on chairs and is not walked on. Contrary to popular opinion you cannot stand there and lift it with a hook and have in the right place. Any reinforcing needs to be 2" from the bottom of the slab.

Calcium: That is old school, the concrete will weep salt crystal to the surface for a long time every time it gets wet, lowers concrete strength, and corrodes reinforcing and surface mounted metals. I am surprised the batch plant even did it as it is a no no today.

Plus: It will cost the contractor 1/2 or less to top a new slab than tear-out of the previous. If he wants to got to court be sure and get your credentialed concrete expert witness and ope your wallet for your lawyer.

Concrete is now a science that is mature but improvements occur every year, experimentation and testing are a continuous process. Become the resident expert: go to Amazon books and buy "The Contractors Guide to Quality Concrete Construction" It is only $83, cheap education. I have given many away to friends planning concrete work.

Ron