The 4' wide concrete walkway to my front door has become stained and
unsightly. Part algae, part burn marks from burning palm seeds dropping on
it, part just a discoloration of unknown origin.
If I use Clorox bleach on the concrete, that would be as starting point to
clean it up. My question is, will chlorine harm the concrete?
We don't know how deep and severe they are. It will etch the surface
like the pressure washer. There are various blast media that are less
abrasive. A local could help with the answer.
Perhaps an acid etch and stain would be the less costly approach.
I agree with Bob. The bleach can kill it, but it will still need to be
removed and that is the job of the power washer.
When it comes to power washers it is all about BOTH the PSI -and- the
Gallons per minute.
Very true. Most powerful machines have a means of reducing the pressure
or you can simply stand back a little more. But if the machine does not
have what it takes to start with, there is nothing you can do. Frankly most
people only look at the psi and never give a though to the volume. The real
point I was trying to make was to be sure to get enough pressure and don't
ignore the volume as most people tend to. Most consumer machines have OK
pressure and poor volume.
I should have been more clear with my original answer.
Since most posters suggest pressure washing, would my 1800 psi 1.7 Gal/m
washer hack it? Might be worth a try.
Otherwise, I guess I could stain or paint the concrete to make the blotches
look more uniform.
never ever paint concrete, its a slippery every year maintence
whatever you do the seeds, which i am not familiar with can do it
some things are better ignored because the possible fixes arent wort
the money time hassle and dont last
washing. Trouble with concrete is that you
can write your name on it with the pressure washer, eroding the
concrete, and not get all the stains. I would try
scrubbing with 1:10 bleach/water, or just hose it on with a hose end
sprayer. Bleach doesn't bother our plants, as
I have used bleach on the outside of our condo, but I would rinse area
well. For the burn marks, if there aren't too many, you might try
some acryllic paint to camouflage them........I did that on a concrete
deck in our atrium after a neighbor
got walnut stain all over it. It is sheltered and not a lot of sun or
weather, but it stays on concrete. I used
small bottles of craft paint and just mixed it to get the color right.
Stain maybe if you get that concrete really really clean first. Don't
paint. The only painting of concrete I would recommend is the cement floor
of a garage and then only if you are ready to do the intense prep that it
requires for a good job and if you buy the expensive top quality true two
part epoxy materials.
Sandblasting certainly will get it clean. However even home
sandblasting can damage the concrete. They typical sidewalk will have been
finished to bring some "cream" to the surface of the walk to provide a
strong smooth surface. The sand blaster can eat through that.
I would reserve it for the final try. I have some curbing that has been
very difficult to clean. I have been holding off getting the sand blasting
outfit out, but I may do it this summer. I will cut back on the power
Probably not, but the chlorine may harm other things in the runoff
(trees, shrubs, grass, metal, etc). I wouldn't go any higher than 1
cup Clorox per gallon of water. A pressure washer with plain water is
the tool to clean concrete.
Don't waste your time. Go to a janitorial supply store, rent one their
hairiest power scrubbers and buy the compound they recommend for
cleaning concrete. Take it home and work your butt off (been there,
done that). Rinse it off and let it dry, then if it looks decent,
apply a sealer from the J. S. store. If successful, take better care
of the walk. If not, tear up the walk and replace with something more
compatible with your eco system, like pavers or some such. HTH
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