Hi everyone,

 

For context, this is my first concrete project and I'm looking for some advice around finishing. I used the Buddy Rhodes ECC blend in a semi-flowable mix, with acrylic/PVA fibres and scrim added. The countertop was cast-in-place, with substrate/edges built out of form ply. Since removing the forms I've given it a light hand sand with 220g, just to take the edges off. Nothing else has been done to it.

 

The edge forms were removed about 1 week ago and I'm keen now to move onto finishing, however I'm slightly unsure about how best to go about it. I'd like to keep the lightly burnished 'cream' look, however would prefer the top working surface to be flat and smooth (currently the texture on top is quite rough from the troweling). Ultimately, the finish I'm aiming for is a raw, lightly burnished concrete, with smooth matt top.  

 

To achieve this I was planning to firstly fill the holes in the edges with Buddy Rhodes Bone Paste, then either lightly sand the entire countertop using a handheld random orbital sander, working through 80g - 400g, before sealing. Alternatively, I thought it might be better to just polish with a 200g/400g diamond pad, either wet or dry, then sealing. I'm looking to seal with either TK6 NanoCoat in low gloss (worried it may still be too shiny for what I want), or Surecrete's XS-327.

 

Any advice or feedback on how best to achieve the desired finish would be very much appreciated.

Cheers,

Chris

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I would probably start polishing at 50grit then work up to 400grit. But hard to say by the pictures how flat your top is. I am guessing if this piece is a couple weeks old its probably a little to hard to take all the imperfections down with a orbital sander. But like I said tough to tell how flat it is by pics. You could also open it up with acid then sand with your orbital sander.

Thanks Josh, that's helpful!

I've captured a couple of photos to show the worst of the surface, but acknowledge that it's still difficult to see. I'd describe it as reasonably flat and consistent, with minimal fibers showing and a few rough spots that are maybe 0.5-1mm deep.

If I start polishing at 50g, will it remove the cream layer entirely? I'm trying to ideally preserve the raw, lightly burnished look, while smoothing out the top slightly to create a practical working surface. Also, do you think I could attach the polishing pads to my orbital sander and just dry polish, or would you recommend I hire a wet polisher?      

Thanks again - Chris

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I see so If you don't want to remove cream layer I would start probably at about 200 grit with your orbital sander and go to 400grit. Do you use densifiers? I would sand at 200 grit to open the concrete then put a densifier on it then sand with 200 again then 300 then densifier then 400 then densifier then 400grit and seal with ICT! But ICT is just my choice. Putting diamond pads on your orbital sander will probably not give you the desired finish you are looking for I would not recommend doing this ever. I also would not recommend wet polishing.If you want to keep the look fill the holes and sand.

Chris,

I would agree with Josh.  First these tops look very nice, good job for a first time trying to pull off a nice finish trowel finish.  

Here would be the steps I would recommend, I do understand your uneven surface and it can be evened out nicely.  Start by hardening the surface, I would soak them for about 10 minutes with a ChPrep diluted with 50% water.  This will soak into the concrete nicely and harden the surface to prevent further scaring with sanding.  A micro fiber sponge works great to do this.  I would then cover the piece with the BR paste, as you planed on doing.  Once the slurry dries overnight, use your ROS do sand off the any extra paste you leave on the surface and smooth the total finish, a 200 or 400 grit should work nicely.  I would then soak the tops again with the diluted ChPrep to really harden the slurry with the rest of the countertop.  Let this go overnight.

My choice would be to finish the sealing with 1 more good wipe on of ChPrep, then if TK6 is your preference this would the be time to use it.  If not, then I would finish the counters with ICT for a durable product.  

Thin applications of Tk6 will work with ICT, after the Prep process if that is the direction you want to go.

Feel free to contact me on FB and I will give you a call if that would help.  

Jon

Awesome advice, thanks guys! I'll follow the suggested steps of ChPrep -> slurry -> sanding -> CHPrep/sealing. 

 

From a DIY POV I'm a little scared by the ICT process (particularly temperature control), but seems it's the way to go. Jon, I watched your vids on the application and it's all fairly clear, however I've got a couple of quick questions if I may:

 

1. Do you prep/seal the edges in the same manner as the top surface?

2. I assume the final coat of ChPrep (prior to ICT application) should be done at 100%?

3. When all the prep/sealing is complete, would you suggest running over the entire top with a high grit burnishing pad and wiping a vapor coat of 100% Clean & Set?    

4. Is there an easy way to control temperature through the process without a thermometer, or does it need to be highly precise?

 

Many thanks for your help.

Chris, trust me I hear this many times. I believe you will find with anyone that is using ICT it is a pretty easy system.  

Send me an e-mail and I will send you a copy of the instructions of how we apply in our shop.  But to answer your questions.  jon.schuler@yahoo.com

1. We do all the surfaces first and finish the surfaces, then concentrate on the edges when we are done.  We just find it easier this way.

2. yes, only the extended dwell time soaks are done with the diluted 50/50.  After that 100% concentration is used.

3. Sure, we use either a wool bonnet or a 1500 to 3000 cps pad works great.  A hogs hair pads works very well as well to give the finish the final pop of sheen.  We set our buffer (Makita 9227C) on 4 for our final buff.

4.The application temperature is 70 to 90 degrees.  If these pieces are already in place then simply keep the room warm and you will be fine.  

We just finished a CIP job on a new constructions.  The first diluted applications were done to 65 degree concrete tops, as the job site is not fully heated.  When we came back to apply the final wipe on applications I used a small roofing torch just to bump the concrete temperature up about 10 degrees.  It only took about 5 to 10 minutes to heat up the pieces, pretty easy and quick to do.

Here is what we use when we need to bump up the concert to a comfortable application temperature:  http://flameengineering.com/collections/roofing-equipment/products/...

Perfect, that's cleared-up any lingering confusion.

Thanks again to both of you for your timely replies - your advice has really been appreciated.

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