How do I get water stains out of a porous, stained concrete floor?

I would try CLR.

It looks like a can of paint has been sitting there? If so, you may be able to 'float' the stain off the concrete. If it was an oil based stain, then plenty of mineral turps on a wet sponge or cloth.

If not paint, or not an oil based one, try a pretty sloppy paste of bicarb soda with a smallish amount of white vinegar, Allow it to sit as long as you can then draw it out with plenty of dry paper towels.

And those paper towels can then be used in your compost bin or around the base of citrus tree to keep pests at bay!

Try Borax! It does a lot of different things!

Did you try TSP?

I would also try Borax...

Since mayonnaise works on furniture maybe it might on concrete. Guess it can't hurt to try.

Vinegar and baking soda or vinegar and borax I would make it into a paste and let it sit for a while and scrub it

Try mureatic acid. Cover it with burlap or cloth and pure a little every hour for 5 hours. Then remove cloth and rinse.

Maybe try a little paint to match concrete, and blot in a little at a time. You also, may have to thin paint out. Looks like the color has been rubbed out of the concrete. Hope this helps. Anything else properly will wash it out more.

Thanks to everyone who took the time to reply to my question. I will surely find a resolution to my problem with so many good suggestions. Thanks again!

Gary

I haven't tried this technique on regular cement, but I have tried this to remove stains on terrazzo floors, which are made of marble chips mixed into Portland cement, polished to a very smooth finish.

I found the following technique after pouring through countless internet blogs - and it worked perfectly for my terrazzo floors.

First, I thoroughly cleaned and scrubbed the floors to remove old waxes and sealers.

I purchased a powdered hair bleach and crème developer at a hair supply store and mixed the two together into a paste, as you would if you were to bleach your hair.

I then applied the hair bleach paste very thickly onto the stains and applied heavy-duty plastic over the hair bleach solution and taped it to the floor. The airtight plastic over the hair bleach paste slowed the drying process of the bleach solution, so that it worked as a poultice to draw the stain out of the Portland cement into the bleach.

After about 5 to 7 days, the bleach paste was dried to a powder - full of the former stain! If the stain has not vanished completely, repeat the process again. I remember having a couple of large stains that weren't completely gone after the first treatment.

This worked a miracle on my terrazzo flooring. They were a beautiful, stain-free creamy color when I finished bleaching the stains

After the stains were gone, I applied many coats of a high traction sealer, then a finishing sealer (also high traction) to keep the floors slip-proof, stain-free and glossy. (Unfortunately, I was unable to find a diamond polisher to rent and again had to be resourceful.)

As luck would have it, after I worked very hard to restore my floors, best I could in an amateurish way, I learned about a nearby company that would have professionally restored them in the proper way...

If all else fails, you could try this technique, but I don't know how it would work on regular cement.

Just cleaned a garage floor, utility room floor and a shop floor with all kinds of stains. Muriatic acid worked best. Got it at Lowe's Home Improvement store. Be sure to have the area well ventilated while using it. I had a oscillating fan going and a hose ready to rinse area afterwards. Cleaned all spots.

Don't ever use clr on stained concrete. I ruined my floor doing that.

Spray the water spots thoroughly with the vinegar solution, saturating them completely. Let it sit for five minutes.

Scrub the stained areas with a nylon-bristled scrub brush to remove the stains. Spray more vinegar solution if it dried up.

Rinse the concrete with plain water.