Bricks, Masonry, Asphalt and Concrete - concrete deck around the pool

Hi,
I have a concrete deck around my 15 year old pool. It is holding up very well, with a couple crackes that developed at one end the first winter(settling), but the crackes are tiny and not a problem.
My question is that in one corner under an evergreen the concrete has turned a little blackish. And around the rest of the concrete it is a bit dirty looking.
What do you people think would be the best way to clean this up. I was thinking mixing some bleach and some kind of soap, and making a solution and trying to scrub it. What do you people think is the best thing to do. I really donèt want to fool with muriatic acid and then have to re-seal the concrete.
I await your answers. Thank you very much.
proud father of a former Marine(but still a Marine)
George

I would try a mixture of bleach 25% in water with some tide. Wet the surface, apply some solution and scrub in a bit. Let it sit for 5 minutes, and hose clean. This should clean the concrete and remove the mildew. Be sure to rinse any nearby plants that come in contact with the solution, as it is quite caustic.

Hope this helps.