I use this method on my concrete aggregate deck:
EZClean 15 in. Surface Cleaner (pressure washer attachment)
Gas Pressure Washer
Pump Sprayer with undiluted bleach
Wet-Dry Vac
A helper (nice but not necessary)
I purchased an EZClean 15 inch Surface Cleaner to attach to my pressure washer, as I have a large amount of concrete in the form of courtyards, walkways, patios and a very large driveway.
When the day came to clean my pool deck, I moistened the deck with water via a hose. Then, I put straight bleach in a pump sprayer and sprayed the pre-moistened deck, and allowed it to sit for about an hour in the early morning hours. I wouldn't do it in the direct sun, as it wouldn't seem to be as effective.
When using the EZCleaner, the water will kick out one way, it's best to test which way it will go so as the bulk won't go into the pool. Work it so the water, debris, sand and whatnot will head off the deck or into a drain. If the water pools up too much, you can either stop periodically and use a wet-dry Vac to clear it away or have a helper suck up the debris as you continue on.
I searched on google for the EZClean 15 in. Gas Surface Cleaner, and there are a few videos. YMMV!