So, I've been wanting to redo our countertops with polished concrete, but it's a significant job. I decided to first try my hand at making a concrete computer desk. My main struggle was that I don't want to invest in the polishing equipment for a one time project, so I set about trying to come up with a way to make a polished concrete look, without actually having to polish the surface. My first stop was instructables.com, where I found several references to Cheng Concrete, which led me to chengconcrete.com. These two resources helped me along my journey.
Here's what you'll need:
3 60 lb bags of 5000 psi concrete.
2 Boxes of Cheng Concrete Countertop Pro-Formula Mix.
1 3/4" sheet of plywood.
2 8' 2x2 or 2x4.
2 Pieces of scrap lumber to make molding radius.
1 8'x2-1/4" silicone concrete edge molding.
1 3'x4' dry-erase white board.
2 Sturdy sawhorses.
12 2" x 5/16" bolts.
4 1/2" x 27" hairpin legs.
1 2-1/4" piece of 1-1/2" pvc.
Step 1: Come up with a plan.
I struggled to find a way to develop a high-shine finish, without actually polishing the concrete. I wanted it to be as smooth as glass, which led me to my first idea, a pane of glass. However, after reading the information on chengconcrete.com and instructables.com, I realized that I was going to have to beat the heck out of the form in order to vibrate out all of the bubbles. And I know me. That would result in broken glass. My next thought was to use melamine and fiberglass the surface, but then of course, to get it perfectly smooth I would spend a ton of time sanding and polishing the fiberglass surface, which wasn't any easier than polishing the concrete surface, so that was out. Finally I settled on using a big white dry-erase board. Although they are available, I had a hard time sourcing a reasonably priced 4'x3' white board. If you do this, make sure that you see it in person (i.e. don't buy it on line) and make sure that the surface is as close to perfect as possible.
For the edge I decided to go for a split-face rock surface. I bought the silicone molding on eBay. I wanted the table to be about 28"x44", so an 8'x2-1/4" piece was perfect, since the back face of the desk would face the wall and needed to be flat. For that I used a 2-1/4" piece of the same dry-erase board cut to length.