Concrete Countertops

[f350ca]

Finished the grinder, seems to work quite well.

But quality control isn't happy with the top layer of cement.

Not sure what happened, the coloured cement seems porous and as a result not very strong, the grinder is pulling some of the stone out. May be able to squeegee a thin coat of portland slurry over the ground surface before polishing. Was getting dark by the time I finished so no photo's of the surface.

[TomG]

Perhaps too much water in the mix? I cast my living room fireplace in concrete and had to re-do a couple of pieces for that reason.

BTW, what happened to QC's tail?

Tom

[f350ca]

If anything I may have kept the mix too dry but I don't think so. It formed a slurry on surface but sure no water came to the top.
Have to check tomorrow with the concrete place I got the water reducer from, he called it a plasticizer, they use it when they make concrete blocks, he said something about making micro bubbles to help reduce shrinkage. Come to think about it cement blocks look porous on the surface.
Good catch on Sadie's tail, must be swung off to the side, there's usually no hiding it.

[f350ca]

Finished the rough grinding. Not impressed with the quality of the cement but I think I can pull a product out of them.

Have worked a coat of straight portland into the surface to level it out, now need to try polishing.

[Mayhem]

I hope it works out for you greg

[Micktoon]

My fingers are crossed for you too, it deserves to work out for the amount of work you have put into the project. Hope it comes out for you.

Cheers Mick.

[DaveH]

Fingers crossed Greg

DaveH

[f350ca]

Thanks for the finger crossing guys, I think it worked.
Set up a wet table to polish on,
These are two of the pieces with the portland worked into the surface.



First stage of polishing with 50 grit pads, looking much better, still need to work another layer of portland into a couple of spots but looks like a sellable product.



Quality control looks like she's hiding her head though, not sure we'll get the final approval.

[TomG]

Looks pretty good from here Greg.

Does the surface stay pretty flat when you polish given the varying hardness of the cement vs. the stone? That rear cross section looks a little scary, hopefully there's enough steel in it.

Tom

[f350ca]

The marble chips are harder than the cement, so they carry the pads as you polish. You can detect the cement is undercut but not a noticeable effect. Yah this piece is fragile, they wanted a massive sink, I wouldn't want to fill it with hot water.