You may want put concrete adhesive (you can find it in hardware stores, like Home Depot) on your existing concrete, then lay the pea gravel. Then put a sealant over the gravel to give it the shiny/wet look and seal it in place. A good site with concrete information is: http://www.wrmeadows.com/wrm00025.htm

I'm planning on doing the same thing, except just as a patio. Good Luck!