Weird Spent Sealer

Doing a concrete cleaning job for a 50 year old building. Pretty straight forward, 20,000 sq ft basic cleaning. Had one section about 200- sq ft that looks like at one time it had a coating or sealer of some kind. Someone put something down and mopped it around breaking down the sealer. They did not pick up the door mats so the original coating is still on the surface at those spots as evident by the water beading only on those areas. The client is happy with the cleaning, but would like to get the mop lines out if possible. Was doing expansion joint repair as the second part of the job so I told them I would test several strippers and see what works and I can give them a price to treat that area as a separate job. They are great with that. Problem is, I can seem to find a stripper that will touch it. Here is what I have tried -

  1. Prosoco Seal and Cure Remover
  2. Prosoco Fast Acting Stripper (their strongest stripper)
  3. Prosoco Dicone NC15 - this is a silicone stripper
  4. 40% Sodium Hydroxide mix
    Nothing phases it at all. Anyone have a suggestion?
    Here is the spot under the mat showing the water beading. This “proves” some coating is on it.

Here is the main area showing the spent sealer mop lines

Might be water based sealer try muriatic acid do small test spot

That BrownStuff from pressureworks indicates it strips wood decks of sealer, maybe it can do what you need it to.

It may but depending on his location he may not be able to get it. They dont ship their products

I can get it. I believe it is primarily sodium hydroxide (one of the most common chems in strippers). I tried a 40% sodium hydroxide mix (btw - I do not recommend people make a mix that strong. It is dangerous stuff - my pump-up was dancing around and didn’t last more then 30 minutes after).

Its worth a try but I thin muriatic acid will be the solution