Coal in concrete

[swaggywaggy]

Has anyone ever heard of coal in concrete I was cleaning my freshly poured slab inside my new pole barn and noticed little spots in the floor with black stuff coming out of them. So I talked to the contractor and he tells me there's coal in it and its the concrete company's fault but he would help me take care of it by calling them and having them come check it out. He said he has seen this once before and the company took care of it by skim coating it and paying for a epoxy floor covering. Any help would be greatly apreciated

 

[rsanter]

I have hear of wood chips because they were using crushed concrete as aggregate and there was wood junk that got crushed in the mix

Bob

 

[LegacyIndustrial]

Skim-coating is weak and would need to be ground off prior to epoxy coating.

 

[Bib Overalls]

I have not seen that but I am not surprised. In some areas mine tailings are used for aggregate in concrete. No big deal if it comes from a gold mine but if you are in coal mining country there could be a problem at times. Did you order fly ash in the mix?

 

[Thedroid]

Coal is added to cement grinding ball mills in order to clean them out before certain maintenance operations. This is the most likely source of the coal.

 

[RAYJAY]

coal is very soft, not like gravel , wounder what it did to your structural property's of the concrete

 

[ConCretin]

I wonder if your contractor is referring to fly ash, which is a supplementary cementitious material produced by coal burning power plants. Concrete producers replace a portion of the cement in their concrete with fly ash because it can enhance the characteristics of the mix and is slightly less expensive than cement.

I've never heard of fly ash containing actual coal but I suppose anything is possible. Seems very unlikely though.

 

[swaggywaggy]

Not sure if they ordered the fly ash with the mix the contractor told me ky state laws allow 2% coal added to the mix he also said it would float to the top and now it's leaving little pits. It's a 30x 40 pole barn and there's prolly around 50 spots

 

[swaggywaggy]

Here's some pictures

 

[swaggywaggy]

Here's a close up this hole is about the size of a dime

 

[ConCretin]

I found an article that appears to describe your issue;

http://www.concreteconstruction.net/concrete-articles/lignite-coal-causes-surface-problems.aspx

Unfortunately, it's too late to follow the advice provided for dealing with the problem. Even so, I wouldn't willingly accept the slab. I'd raise hell with the supplier AND the contractor.

 

[Red05GT]

Here in southwestern Ohio the ready mix supplier we use has had a problem with their
gravel mix containing a black shale which when used in exterior flat work has a tendency
to pop out after winter. The solution has been to pay extra for limestone aggregate mined from a quarry.

 

[swaggywaggy]

Welp im waiting to bear back from the contractor he called the supplyer this morning and there coming out to check it out. And yes they did order fly ash with this batch. I was wondering if i had any legal rights if neither the supplier or the contractor will fix

 

[swaggywaggy]

Ok so I talked to the concrete supplier and he said he would take care of the problem by coating down a epoxy floor. He said he usually uses the valspar that lowes has to offer but if I had a preference I could use anything I like. So I guess my next question is what's the best epoxy floor out there since someone else is footing the bill ?

 

[LAROKE]

I've only seen coal used with concrete (on purpose) in a Bruce Goff house

 

[retfr8flyr]

For a really good epoxy you will want primer, base coat, flakes and clear top coat. When you start talking with your contractor about $2000 epoxy jobs, instead of $200 from Loews, he will most likely change his mind.

I would contact Fred with Alpha Garage, Justin with GarageflooringLLC and Scotty with Legacy Industrial about what's best for you.

 

[swaggywaggy]

So, I've decided against the epoxy floor instead the supplier is gonna refund me for half the concrete so I was ok with that. So my next question is when we were hangin the garage door it left little scuff marks from our boots on the fresh poured slab I'm gonna seal the concrete and was wondering the best way to get those out or not worry about them I'm gonna use Kure and seal WB

 

[LegacyIndustrial]

Fill with a good epoxy based filler. Seal afterwards.