concrete patio - green gunk growing

We have a concrete patio that is somewhat shaded by the house from the afternoon sun.
We have a problem with green gunk growing on the surface... because after it rains, the water does not get the sun to dry quickly... so green gunk.
After we power wash the patio, is there something we can put down to help seal or inhibit the growth. I think I've read about the usual sealers being not good as they cause the concrete to become slippery when wet... along with the need of the concrete to "breathe"..
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On Tue, 15 Jan 2013 22:25:31 -0600, "ps56k"

I'd try washing it down with clorox & see if that is enough.
If the patio was done right, with a brush finish, no amount of sealer will make it slippery. [epoxy might-- but sealers will soak in and leave the texture.]
Caution with the sealer-- It is a *sealer*. It will seal in, not cover up, any stains, dirt, vegetation-- Make sure it is *really* clean before you seal it.
Jim
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On 1/15/2013 11:25 PM, ps56k wrote:

Florida? Lots of green mold there, and more, IIRC, when palms are blooming (lots of shed pollen). Concrete grabs dirt and organic stuff because of the rough texture, and sealer won't change that. I'd throw some bleach on it, rinse, and forget about it. If water pools on the patio, sweep it off after rain. Lots of folks put tile on their patios, which might lessen the mildew/mold growth. Then you only have to worry about slipping or sealing the grout :o)
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Consider calling a 'slab jacker' and have the concrete sloped enough to drain as it should have in the first place. No water = no green growth (with luck). The process will not affect the surface, just tilt the masonry a bit.
Joe
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