I am planning on purchasing unfinished furniture, painting two coats of water-based paint, then applying a coat of coarse pumice gel mixed with paint and applying on furniture to give the furniture a more concrete look. Do you have any suggestions? Will the gel stay on the oak furniture without chipping and peeling?
As long as you achieve proper adhesion of the wood to the paints first, the Coarse Pumice Gel (CPG) should hold up fairly well. After applying the paint, lightly sand and wipe clean (with damp cloth) before applying the CPG.

Add about 20% of the GAC 200 into the Pumice Gel to increase the adhesion and strength. You may wish to experiment with several blends of CPG and GAC 200 to see which combination offers the toughest surface and yet still looks like concrete.

Allow the CPG to dry thoroughly. I'm guessing at least a week. You may also want to seal the surface with Satin Polyurethane, but there are lots of ones that yellow severely so choose wisely. There are no guarantees with something like this, and how well it will hold up, and for how long, will depend on how much wear and use the furniture will endure.