Making Your Concrete Driveway More on the White Side
If you have access to a power washer, it's probably the
Oil & Grease
Fresh Oil -- The universal solution for fresh spilled oil is kitty litter. If you change your own oil or your car leaks oil, keep a bag of it in the garage and put a handful or so on the oil puddle. If the oil spill is recent but, has already soaked in, this stuff will also draw some out of the surface so, try it before going to the next step.
Old Oil -- This one's harder. People do different things for oil that has soaked in. I saw a test on TV where they divided a large, seasoned stain into four areas and tried different methods on each area. They worked all cleaners in vigorously with a push broom.
On two of the areas they used home remedies. One of these was Coke. It didn't do anything. The other home concoction was a mixture of laundry soap, with either bleach or ammonia and TSP. Also, little improvement.
On the other two areas they used Gunk brand degreaser (which is what I've always used) and Swab a driveway cleaner product made by Gunk. NOTE: This was not a Gunk Commercial.. Both improved the situation but did not clean away the stain entirely. The driveway cleaner did a better job but was more trouble to use. The degreaser left an undesirable wet looking sheen, the driveway cleaner didn't do this. On alt.home.repair I've seen good comments about Castrol SuperClean and a similar (maybe the same) product called PurpleStuff. A likely place to find Gunk or Castrol SuperClean is an auto parts store.
Here's a novel proposal. I don't know anyone who's tried it. It's not obvious to me why it would work better than a combination of the above methods, but who knows.
Michigan State University Extension Service says ". . wet with clear water. Apply a hot solution of 2 to 2 1/2 ounces washing soda or 1/2 ounce trisodium phosphate per gallon of water."
There's no completely safe method. You probably want to start easy and move up to the ugly
stuff. If you have colored concrete you should test any method on an inconspicuous
spot to see if
it affects the color.
Oxalic acidremoves rust stains from most things. A grocery store cleaning product named ZUD contains it. Trying this would be the mildest approach. I have removed some pretty longstanding rust stains on our walk by wetting the area, then sprinkling liberally with ZUD and spraying it until the powder was wet. I let this sit for a few minutes, then scrubbed it with a brush. Repeating this a couple of times removed the rust stains.
Real oxalic acid is often sold as wood bleach, a powder -- check the ingredients. Dissolve in warm water until saturated. ('Til no more will dissolve--residue of powder on bottom of container.) Brush on. Let sit for several minutes. Rinse thoroughly. It's mildly toxic. Use rubber gloves, goggles and keep a hose or bucket handy to rinse it off skin quickly.
If this doesn't work go to Almost Any Marks or Stains below.
Dirt and Mildew Stains
I clean mine with a water blaster/power washer followed by spraying with a 1:2 or 1:3 bleach water solution. If you don't want to use a power washer dave_fr from alt.home.repair says Jomax and bleach does a good job.
The only thing I know to do for this is use a power washer. If you know another solution please let me know.
For white crystalline or powdery deposits go here.
Almost Any Mark or Stain
If nothing above works you have to go for the ugly stuff--muriatic acid (dilute hydrochloric acid). Try it cut about 4 to 1 first. If this doesn't do it then, move on to the strength it come out of the bottle. This stuff cleans by etching away the concrete so, you want to rinse it off as soon as the stain's gone.
WARNING: When they say ACID! this is the kind of stuff they mean. Be very careful. Protect your eyes, face, hands body, etc. When diluting, pour acid into water--never pour water into acid. Have a garden hose ready to flood any areas it gets on that it shouldn't.