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Bhoward 11-16-2008 06:42 PM

New cememt patio stained by wet leaves
My cement patio was replaced about 6 months ago. My patio doesn't get much sun on it during the day and I have noticed now that the leaves are coming down they are staining the patio after it rains. I try to get the wet leaves off as soon as I can but not always possible. The patio is now stained in a black color with blotches all over . I have called the contractor back who poured the patio, but I just wanted to get some background as to why this might be happening, Since I have no experience with cement I wouldn't know the truth from an excuse. It seems the only way of cleaning up the blotches is power washing the patio, which is not an option since I live in a Condo and I'm sure the water has been turned off by now. (I live on Long Island, NY) Should this patio have been sealed after it cured? The contractor said nothing about sealing it after the job was completed. Thanks in advance for any insight about the stains.:)

rjordan392 11-16-2008 07:27 PM

Yes, it should have been sealed. I think concrete needs a couple of days to dry out before a sealer is applied. You can find out for yourself by checking the sealer bottle instructions. With the weather as it is, you might have to wait till Spring to either scrub out the stains or use a power washer.

dorothyolive 11-16-2008 11:12 PM

The power washer will work. I've had the same problem. I haven't sealed the patio yet. Also, common household bleach works to remove the stains. Be careful with the bleach though, it will kill your lawn.

Bhoward 11-17-2008 08:22 PM

Thanks for your reply, I'll check back and let you know what the contractor says when he comes to look at the patio this week. I wish the contractor would have said something about sealing when he finished the job. I never heard of sealing concrete before. Thanks again for the comments.

yes.itsconcrete 11-18-2008 09:29 AM

most conc's NOT sealed other'n curing agents, etc,,, usually these're paraffin based, control the rate of hydration ( curing ), & do NOT provide stain protection,,, your patio's no different than any exterior conc - susceptible to dirt,,, because it doesn't get sun, leaves can stain it.

we use clr, lime-away, bleach, muriatic acid, or dawn dishwashing detergent,,, sealers now avail in ny have low or no voc's therefore you're restricted to lo-grade sealers that must be replaced/restored annually,,, a better solution, impo, would be cleaning & applying silicone siloxane.

be prepared to pay more as this isn't a normal part of conc replacement,,, btw, cement is an ingredient of concrete,,, btw, stains're always more noticeable when conc's new rather'n aged.

Bhoward 11-18-2008 05:24 PM

Thank you so much, great information. I now have some background when I see the contractor.:thumbup:

Nestor_Kelebay 11-18-2008 07:20 PM

I can't help but think that the only black or "blotchy" stains you could get on concrete would be from mildew growing on/in/under the wet leaves. Mildew can live a long time between exposures to moisture, so it won't disappear just because the concrete dries up. However, mildew, like everything else on this planet also needs a source of food to survive, and as long as you remove dead leaves and such ontop of the concrete, the mildew can't survive without food.

As was previously mentioned, a 10% solution of bleach in water will kill any mildew in your concrete, and you can just spray it on with a hand held spray gun. If the bleach kills it, then you can be certain it was mildew or mold, and not just ordinary dirt.

You should be aware that putting a coat of sealer on your concrete will make it more slippery when wet. You might be much better off putting something like polypropylene carpet on your patio. Polypropylene is the most water resistant fiber used to make carpet from. All Indoor/Outdoor carpet is made from polypropylene. Carpets called "Olefin" are made of polypropylene as the word "olefin" means a double carbon=carbon bond, and the only carpet fibers you find those in are those made from polypropylene. You cannot dye polypropylene by conventional means. The only way of colouring polypropylene plastic is to add tiny coloured particles to it before drawing it into a fiber. Since the coloured particles are encased in the polypropylene plastic, you can use harsh chemicals like bleach straight out of the jug on a polypropylene (or 100% Olefin) carpet without harming the carpet. Ditto for strong solvents like acetone and lacquer thinner.

In my opinion, a better solution to sealing the concrete is to put a 100% Olefin carpet over it. That will give you good traction when the patio gets wet, and if the mildew from leaves starts to grow in the carpet, just spray the carpet down with a 10% bleach solution, and you're good as new.

If you feel that installing Olefin carpet over your concrete is a plausible alternative, you would have little to lose by buying one of those car floor mat size samples of 100% Olefin carpet and torturing it with bleach just to confirm for yourself that it won't harm the carpet (but will kill any mold or mildew living in that carpet).

yesitsconcrete 12-03-2008 11:35 AM

:huh: not sure how it happened but forgot to post this, also,,, had our d/w replaced last yr & we've had the same thing happen - yucky leaf stains :furious: called the contractor to complain but then remembered i did it myself :censored: conc does get dirty when its outside as i recall :laughing:

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