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I've been searching google for awhile but can't find a straight answer (every link is about walls/floors):

Can I polish (or sand to be smoother at least) a concrete pier block?

I have this one from Home Depot. I want to put it somewhere where it will be exposed and currently they are extremely flaky on the bottom (and somewhat sharp even) and a bit smoother on the sides. I would like it to be smoother so it looks nicer and doesn't shed everywhere. Then I plan to seal it to protect it from the elements. Is this possible or is this type of concrete not right for sanding/polishing/sealing?

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    If the concrete is still in good shape yes. It doesn't cost much to try... – dandavis May 30 '18 at 5:15
  • If it's flaking, that's a red flag. It may continue to flake after the grinding/polishing process. – Bryce May 30 '18 at 17:43
  • I don't think I've seen a single one that is not flaking/rough on the bottom. The sides and top are not flaking. I'm open to pouring my own, but that is a lot more work than trying to make one of these work. Just wanted to see if its feasible before investing a lot of effort in sanding. – James Jun 1 '18 at 19:01
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Definitely can be polished!

Step 1. Grind the flaking on the bottom with a 3"or 5"diamond cupwheel any grit will work. OR JUST CHIP AWAY WITH HAMMER AND SCREW DRIVER

Step 2. Use polishing grout or rock hard setting powder cement and fill the porosity in the block with a 6 inch metal spatula. It may take 2 coats and let dry overnight.

Step 3. take a 100 grit polishing puck and with your hand smooth the block out. Once smooth use a lithium silicate densifier. I recommend endurapolish by H&C one gallon about $35. apply 4 -5 coats Since its porous. Let dry 4 hours or overnight the longer the better but overnight is more than enough. This creates the hard surface that makes it possible to polish.

Step 4. Polish and Seal, Burnish Polish with 400 ,800, and 1500 or even 3000 grit polishing pucks your choice. You may be satisfied with the 400 grit. Either by hand with a single 3" puck or with 5" polishing pad on a variable speed polishing hand grinder. Note if densifier will still absorb add coats between the stages of the polishing phase. Once satisfied with the mirror shine and look apply and Outdoors UV Penetrating Concrete Sealer preferably high shine or we look. Don't over do it just as apply one thin coat with a microfiber pad or rag. Let dry and burnish with a 5 inch 3000 grit burnishing pad on a hand grinder at a high speed at least 3000 rpms. Repeat as needed.

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You can "polish" the cement up a little and it will be smoother. Although pier blocks are not designed to be polished they are high strength and other than a rough surface they can be buffed up. I prefer painting to grinding but have used masonry grinding disk to shape some blocks in the past. Make sure to. Wear a dust mask as the dust is not good to breath.

  • I did invest in a respirator for this. I don't think I can just paint it without smoothing it out first as the bottom is rough and flakes a bit. The sides and top could be easily painted w/o much sanding. I think the rough layer is potentially just detritus from other blocks (and/or a rough cut since that part is meant to be in a hole?) and I'm hoping I can just hand sand/wash it off. – James Jun 1 '18 at 19:06
  • I have always used a grinder but with patience you could sand it. I would find a out of the way sidewalk and rub it on that or a concrete block to rub it on but it can be done. – Ed Beal Jun 1 '18 at 19:40

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