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