The concrete floor in question is a deep 2 car garage, recently gutted to the studs and transformed into a workshop. The final piece of the puzzle is the concrete floor. The concrete was poured in 1978, and appears to be original, meaning that there doesn't appear to have been any other topcoats of anything applied to it since it was first poured. I was born in 1977, so suffice it to say I have no idea what type of sealer they might have used back then, if any. The concrete has just about every possible type and color of stain in existance soaked into it. Also, there are a few small areas where it looks like some fertilizer granules dropped out of a spreader or something and ate the surface of the concrete just enough to give it 40 grit sandpaper texture. The slab is structurally sound, very hard, and dense.
So far I have used TSP (trisodium phosphate) mixed more than 2 times stronger than the strongest solution listed on the container. I soaked and scrubbed the floor down with this solution multiple times and it quite literally did nothing. It seemed to only clean off the thin film of dust and soil, otherwise the slab looks identical to how it did before I did anything. The only way I know that it did anything at all was due to the solution in the bucket turning brown.
I also used a Rust-oleum epoxy shield degreaser on a number of areas to spot clean and it also did absolutely nothing. I'm not just hosing the spots down and then immediately trying to wipe it off either. I'm letting it soak in really well, at full concentration, even sprinkling TSP granules into the liquid, for 15+ minutes. I am then scrubbing the every loving crap out of the concrete with a heavy duty wire scrub pad, and then washing/cleaning with abrasive sponges. Nothing is happening.
Any thoughts on what I can use to get this slab clean? (power washing is not an option for a variety of reasons)
I was hoping to just deep clean the slab and call it good, but even though the slab is definitely "clean" it still looks terrible. So my next question goes out to those of you with first hand experience working with and applying solid color sealers. If the slab is as clean as possible would I be able to apply 2 coats of a solid color solvent sealer without needing to bead blast, diamond grind, or acid etch the concrete for surface adhesion?
At the moment there isn't money in the budget to properly prep and install a 2 coat epoxy floor with 2 urethane topcoats. If I can't do it right then I'm not going to even bother giving it consideration. I can probably manage to buy enough H&C solid color solvent sealer to apply 2 coats if I don't need to invest in surface profiling, etc.
I appreciate any suggestions you might have. Thank you for your time.