pouring concrete for countertop

[Ozzie_]

I tried pouring my first concrete countertop (an L shaped bar top) down in my parents' basement. I used a high strength bag mix, but I'm pretty sure I made it too wet and overworked it.
I took the forms off after a week and started sanding. I went from 60/80 grit to 100 to 150 with an orbital sander and water.
now, after drying, it's still super gritty! When I rub my hand over it, I keep pulling up a sandy texture, and I'm starting to expose some of the bigger aggregate (1/8'').

Am I doing this wrong? Should I just keep sanding and power through the grit, or am I wearing out my cheap wet/dry pads too fast? Do I need to buy proper diamond pads to get this thing smooth? Help a DIYer out!

 

[icyolaf]

Not sure if I'm right too but that gritty texture that keeps shedding fine sand is most likely a layer of soft cement paste that formed on the bottom of the mold. Regular wet/dry paper is silicon carbide, which is technically the right abrasive, but it clogs up almost instantly when faced with that soft slurry and then just smears it around. I think that's why you are tearing through pads so fast. But the short answer is that yes, switching to a set of proper diamond polishing pads is highly recommended because they are designed to cut through that surface effectively and consistently without clogging. It'll save you time and money on sandpaper in the long run and give you the professional smoothness you are looking for. Good luck!

 

[the reflection]

That's a poor finish on the bottom of the mold and happens easily with excess water in the mix. When you use too much water, the fine cement paste tends to separate and settle which your sandpaper is just tearing right off to reveal the stronger sand grains below. But for a truly smooth finish I suggest you invest in proper diamond polishing pads, which can attach to an angle grinder or a random orbital sander with a special backing pad.

 

[Ozzie_]

if it has too much damage, OP should also consider redoing the countertop. you may need to consider repouring a new countertop
the weakening from the excess water and overworking may make it impossible to achieve a smooth, durable finish