Failed concrete question

[Streetcar]

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

Calcium is frequently used in Ohio for unreinforced concrete. With only one section of slab having problems it appears finishing problem not freezing

 

[Tractor Seabee]

Calcium is frequently used in Ohio for unreinforced concrete. With only one section of slab having problems it appears finishing problem not freezing

In #9 the OP indicated he had spalling throughout. Difficult to evaluate a problem of this nature you cannot see and probably has missing pieces of important information; like, how much excess water was added. Extra water reduces the heat of hydration and accelerates surface freezing.

Ron

 

[ddbackhoe]

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.

Our concrete guy uses Manufacturer & Installer of High-Performance Resin Flooring | Stonhard

 

[Jeepnford]

They sprayed the water out of a pressure tank on the truck with a hose nozzle, no measuring. The last truck I had to loan a pick ax so he could break the concrete out of the chute on his wash out. There’s some sporadic spalling in other areas, nothing like the last pour. We had a pretty good snow last night but might try to get pictures later. I’m about 20 miles away.

 

[ruffdog]

It sure sounds like a mess to me. :confused2: I like my concrete solid, strong, and finished nicely and am willing to pay for it. I like a 6 bag mix with fiberglass/rerod and burned black if it is inside. Hope you find a solution that satisfies your expectations. How will you feel each and every time you walk or sweep that slab?

 

[EddieWalker]

Did you take pictures of the pour, or of the rebar before the pour? I've seen so many pictures on here of rebar laying on the ground during the pour that it's become common. Rebar has to be on chairs, there is no other way to keep it off the ground. If they did not have the rebar on chairs, that is further proof that they finisher didn't do a quality job. Pictures will also show the slump of the concrete to some degree. If it's soupy, it will be obvious if you have pictures.

 

[Industrial Toys]

Too bad. It seems that it's probably easy to take chances with the weather when you aren't willing to take responsibility.

We always made it a point, never to allow calcium in our concrete.

 

[Ford850]

Years ago my wife and I drove by a condo being built by a builder we were working with when planning our new house build. He recommended we pop in there while it was not quite finished, for ideas etc. About a week later he asked if we had time to stop in there. I told him we did, but didn't stay long because rain was coming in quick and we had to head home. I also told him I was surprised his concrete contractor was pouring the drive that day, and they were trying to finish it as we left, before that rain came in. He shook his head, saying they didn't get it finished and it got rained on. He made them tear out the whole driveway and turnaround, and start over. Oh, and it was colored concrete too. Big bucks for sure.

 

[Jeepnford]

Some photos of the worst area.

 

[Streetcar]

Hit with hammer to see how tough it is

 

[Jeepnford]

And the not so bad. It looks worse than it actually is in this photo because there is some dirt on the floor. The concrete from the first photos got worse over time. As you can see, a complete re-pour is out of the question, but that痴 not really what I知 after.

 

[Gary Fowler]

I wouldn't want any part of that for a shop floor. If needed, go to court to get it resurfaced or as Seabee suggested, pour another slab on top of it. Looks like you already have a building put up so that may not work out.
You might be ok by using a Scabbler or bush hammer to remove an inch or so of material and then put an overlayment on top. You would need to make sure that you got all the spalled concrete removed prior to putting on an overlayment otherwise it would just spall off later. You likely need to have a concrete design engineer or at minimum a professional concrete contractor to evaluate the slab for design strength. You can get core samples to test for actual strength done for a few hundred $$ which is what I would do prior to going to court (you will need this to prove damage or inadequate placement by contractor.
From your description several things happened 1) Water was added to the mix 2)Calcium added which is a no-no 3) Concrete was on the truck too long prior to placement 4) Freezing conditions encountered prior to concrete setting 5) Concrete was not covered and allowed for rain to fall on it before it set.

The rain falling on it could have been mitigated by just covering it with plastic but the other 4 items listed especially the freezing definitely destroyed the strength of it which about the only thing you can do now is place another pour on top.

 

[Streetcar]

I wouldn't want any part of that for a shop floor. If needed, go to court to get it resurfaced or as Seabee suggested, pour another slab on top of it. Looks like you already have a building put up so that may not work out.
You might be ok by using a Scabbler or bush hammer to remove an inch or so of material and then put an overlayment on top. You would need to make sure that you got all the spalled concrete removed prior to putting on an overlayment otherwise it would just spall off later. You likely need to have a concrete design engineer or at minimum a professional concrete contractor to evaluate the slab for design strength. You can get core samples to test for actual strength done for a few hundred $$ which is what I would do prior to going to court (you will need this to prove damage or inadequate placement by contractor.
From your description several things happened 1) Water was added to the mix 2)Calcium added which is a no-no 3) Concrete was on the truck too long prior to placement 4) Freezing conditions encountered prior to concrete setting 5) Concrete was not covered and allowed for rain to fall on it before it set.

The rain falling on it could have been mitigated by just covering it with plastic but the other 4 items listed especially the freezing definitely destroyed the strength of it which about the only thing you can do now is place another pour on top.

Point 1Water can be added to the truck if concrete is designed properly.water should not be added during finishing
Point 2 Calcium is only a no no if reinforced. It is common for road use.
Point 3 is correct, concrete should never be chipped out of chute
Point 4 how cold did it get the night of the pour
Point 5 how hard did it rain. I have seen similar damage from down pour, but not light rain
It will be hard to salvage that slab

 

[Deere Dude]

Wow, that is bad. No paint will cover that up. Looks like a tear out possibly. Just a thought, what about leveling compound on the whole floor about 1/2" thick?

Thanks for the pictures.
I really wish you luck with that.

 

[Gary Fowler]

Point 1Water can be added to the truck if concrete is designed properly.water should not be added during finishing (If designed properly and batched properly, water should not be needed. However some water can be added at beginning of the load to adjust for slump as long as the water / cement ratio is not exceeded. Water should never be added after the initial adjustment for slump
Point 2 Calcium is only a no no if reinforced. It is common for road use. Nothing should be added to the mix design after it leaves the plant unless it is specifically part of the mix design ie onsite use of plasticizer which is always added and mixed just before unloading the load at point of use. If you need a retarder or accelerant then the batch plant should have put it in
Point 3 is correct, concrete should never be chipped out of chute
Point 4 how cold did it get the night of the pour Per ACI 318 specs, concrete should not be placed when temps are expected to go below 40F in then next 24 hours unless plans are made to insulate or heat the concrete.
Point 5 how hard did it rain. I have seen similar damage from down pour, but not light rain Again, easily prevented by spreading plastic over the finished concrete Any added water whether added in the drum or from rain will be bad. Light rain could still cause powdering of the top fractions of an inch of the concrete .
It will be hard to salvage that slab

For sure

 

[Jeepnford]

Hit with hammer to see how tough it is

Played whack a mole. What already hasn’t went to pieces seems solid.

 

[Jeepnford]

Did you take pictures of the pour, or of the rebar before the pour? I've seen so many pictures on here of rebar laying on the ground during the pour that it's become common. Rebar has to be on chairs, there is no other way to keep it off the ground. If they did not have the rebar on chairs, that is further proof that they finisher didn't do a quality job. Pictures will also show the slump of the concrete to some degree. If it's soupy, it will be obvious if you have pictures.

The rebar was on chairs. It was done the day before. No photos of the pour, misses most of it except for the end, but it was too stiff.

 

[Jeepnford]

Wow, that is bad. No paint will cover that up. Looks like a tear out possibly. Just a thought, what about leveling compound on the whole floor about 1/2" thick?

Thanks for the pictures.
I really wish you luck with that.

I would be good with something like that or what was mentioned previously, I just don’t know if it would hold up. I’m assuming the top would have to be ground off assuming the rest of it good.

 

[ruffdog]

One time on "This old house", they used a slurry pour to level a basement floor. Maybe something like that?

 

[MickeyDBC]

If you search on youtube for "repair concrete surface" there are a lot of good videos that show up.