I recently replaced a floor drain in my basement around which I had dug out the concrete, gravel and clay soil. When I sealed it back in, I laid down a bed of gravel and sand, and then used a standard concrete mix for the top several inches. By standard, I mean it was a typical Quikrete mix with gravel, sand and portland cement. As I was working the top of it with a float, I realized it wasn't going to dry anywhere near the smooth-ish texture of the rest of the floor. I'm guessing that's not achievable with such a gravely, sandy mix. I was correct; the floor in that spot now has a pretty gritty texture and shows lots of pebbles.
If I can figure out what product would make for a smooth finish, I may just break it out and do it again as it didn't take long and was not difficult. It doesn't need to be sheet-of-ice smooth, but smooth enough that it wouldn't, say, skin a knee if bumped. My assumption at this point is that the pro concrete guys probably lay down standard concrete, but then do the top 2 inches or so with something smoother, like a mortar or cement mix without gravel or pebbles. So here are my specific questions:
- Can I buy a premixed product that will finish smooth?
- How thick should that top layer be?
- Do I need to let the concrete under the top layer completely cure before applying the top layer?
Best Answer
It's a process, not a "special" material. A good steel trowel job can give a glass-like finish on standard concrete. It's partly technique, and partly timing (or timing is part of the technique.) Troweling knocks down larger particles and brings up smaller ones, resulting in a smooth finish. In many places it's too smooth, IMHO - easy to sweep, but also easy to fall on, especially if damp/wet.
On large jobs a 4 (or more) bladed power trowel is used.