On 1/15/2013 11:25 PM, ps56k wrote:
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"..

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 )