Concrete Countertops

[f350ca]

Promise there will be metal working involved in this build.
Time for another revenue generating project.
For someone who doesn't particularly like pouring cement I seam to be doing a lot of it lately.
This is a set of concrete counter tops in kit form. Was a good load for my little Ranger pickup, 15 - 50 pound bags of marble chips, 88 pounds of white portland, 16 - 66 pound sacks of cement mix 4 lengths of rebar, a sheet of square mesh and a weeks worth of groceries, about 2000 pounds. The blacksmith shop is turning into dry storage for the moment.



Will pour them in the shop then grind them flat outside on the sawmill frame. Thats where the metal working comes in, need to fabricate a grinder head that uses a 7 inch diamond faced wheel. Will make it to fit the tracks on the sawmill. I ground the last set in the shop, never again, I was a week getting the dust off the machines.

[TomG]

Greg,

I'm very interested in your technique to pour these concrete countertops, will you be documenting the entire process? I hope to be building a bathroom rustic vanity for the UP North cabin this winter, patterned after the furniture I've been building and I'm thinking a concrete countertop on it would look. I could include some local stones to make it look more at home in the cabin.

Tom

[f350ca]

Certainly can document it seeing as your interested.
I pour a regular concrete base about 1 1/2 thick, it contains rebar around the edges and 6 x 6 mesh through the body. This concrete is strengthened with fiberglass chop and I use water reducer or plasticizer depending on where I get it. Think this makes a big difference, from what i've read micro cracks are common and accepted, I've never had them in the ones I've poured, now it will happen. Then I pour a 3/4 inch layer of decretive stone and cement with no sand. Sand separates the stone chips. I've been using white portland for this part, you can then dye it with powdered dies for mortar. The white base gives truer colours. Again i use water reducer in this mix.
Once this is set the grinder comes in, I cut about 1/4 inch off the top to expose the decretive stone. The first one I did with an angle grinder, worked BUT you need to do this wet and Makita grinders aren't water proof. I had to wear rubber boots and rubber gloves to insulate me from ground. Then its polished with diamond pads to 3000 grit, again wet. I was spitting sparks by the time i was done.
I built a makeshift grinder with a totally enclosed 2 hp motor for the last one, it ran on 5x5 angle on the floor. It worked well but filled the shop with stone dust even spraying the wheel with a garden hose. I also bought a Makita wet polisher, it worked really well, and no spitting sparks.
Will post as we go this time, have the forms built, will get pictures tomorrow.

[f350ca]

While we're on the subject of tools, I used an old vibrating sander with a wooden block attached to vibrate the concrete the last couple of times. Again it works but could be better. I've seen cement pourers use a flexible shaft that vibrates to do footings and walls. They lower it into the wet concrete, and the mix instantly becomes fluid. I assume the end moves in and out. Wonder what you'd need for stroke and at what frequency.

[awemawson]

No the end is merely an eccentric on the end of the flexy so it wobbles a lot. I've an electric one, and one that runs off my road compressor. That reminds me they should both go back on ebay as I've finished with them now :)

[stevec]

I wrote this as awemawson was posting his reply.
"Greg, I don't know for sure but always assumed the business end of those concrete vibrators employed an
eccentric (off balance) weight spinning at whatever was optimum speed."
I used a pneumatic vibrator for a recent job. I applied it to the forms and then along the surface to get it to settle.
I used a little too much colourant but I'm hoping it'll fade.


   

[f350ca]

Thanks guys, I guess I've never researched them, they look pretty simple, why are they so expensive?

[awemawson]

Because your average builder wouldn't be able to make one!

[f350ca]

A little bit of welding was involved in this part of the project.
Here are some of the forms.
The styrofoam strips displace the portland base mix along the front edges, once its set a little they're removed and the surface coat worked into the space. The boxes in the middle of some are for the sinks, not easy to cut out latter. In the second photo I used cores for a rear mount faucet with styrofoam below to thin the concrete enough to mount the tap. 1/2 inch rebar around the perimeter with 6 x 6 mesh welded to it.

[f350ca]

Got some machining involved in this project to make it legit.
Went to the local village hardware store to see if they had any sort of flex shaft or if Nancy the clerk were lend me her vibrator, she wouldn't, claimed she didn't own one so I bought a cheap Chinese dremel with a shaft.
Had some small bearings in the drawer, a piece of 3/4 tube and a printer shaft. Was too lazy to change chucks to make the eccentric so center drilled it and milled away one side. A pipe plug seals the bottom and locates the lower bearing. Which may not last, they run a little warm, unknown quality from a long forgotten source.



A bit of duct tape to mate it up and we have a vibrator.



Seams to shake things up, we'll know tomorrow, the pour begins.