36" Pompeii in DC

[ATK406]

Re: 36" Pompeii in DC

RS, I think I read something from Stonecutter that said a 2-2.5:1 ratio of sand to portland was best and to be sure it was course sand not rounded. Take a look at the latest posts on Gulf's thread for the specific quote/context.

As far as "grinding now" or filling with the slurry I don't know what advantage grinding now would give you, since you will have to grind it down after you lay the slurry anyway. Maybe grinding now would allow you to control the placement of the slurry coat. I'm only thinking out loud...you are WAY ahead of me on this....But I am watching and learing from your experience...Looks very promising so far.

Thanks for sharing.
Regards,
AT

[fallstonray]

Re: 36" Pompeii in DC

Great build! Thanks for sharing.

[rsandler]

Re: 36" Pompeii in DC

Poured my second experiment, face down last night. Hopefully I'll actually be able to get the mat back out!

Russell: Yep, I picked up a bonding agent when I got my other supplies, and I'm planning on using that for my slurry.

AT: I saw that post from Stonecutter too. IIRC the context there was a mix for the whole countertop, but since the slurry in the indentations is going to be relatively thick, probably best to go with a similar mix. For the small volume I need to mix, using a little more white portland is no biggie.

My thinking with grinding before filling with slurry was twofold. First, by getting rid of the little ridges along the sides of the indentations, it might make getting the right amount of slurry in easier. Second, to the extent that grinding exposes bugholes in the raised black areas, I could easily fill them with black slurry, and then any excess white slurry on the raised areas can just be ground away.

I think what I'm going to do is try it both ways. It's an experiment, right? For experiment #1, since I'd really like to deal with the ridges anyway, I'll grind it, patch any holes, then fill the indentations. With #2, I'll fill the indentations right away after removing the form and grind it all together once it has cured a few days.

[rsandler]

Re: 36" Pompeii in DC

Well, I took experiment #2 out of the form just now. Moral of today's story: if you're going to pour concrete facedown onto a mat, make sure said mat is glued down! Thing was buried a good 1/8th of an inch deep...

The pictures tell the story pretty well. Surface turned out nice and smooth where it wasn't chipped and ugly

As an aside, one of the places online that described making pavers using cardboard tube said the forms could be re-used. For reference, this is nonsense. Both times I've had to cut the cardboard to get it off, and then peel little scraps of cardboard off the sides of my paver...

If I dare, experiment #3 will be to try another one face down, but applying spray adhesive first.

[rsandler]

Re: 36" Pompeii in DC

Poured an experiment #3 last night, this time spraying a new piece of mat with adhesive, then sticking it to the melamine before pouring concrete. In retrospect, I should have waited until the glue was well and thoroughly dried before pouring, rather than ~5 minutes while I mixed my concrete. There may be an experiment #4...

Also, Thursday night I did the initial grinding on experiment #1, going from 50 up through 400 grit with diamond pads. Yesterday I applied a black slurry to patch the bugholes, and then filled the indentations of #1 and #2 with a slurry made of 2 parts sand, 1 part white portland, and an acrylic bonding solution/fortifier for most of the liquid, with a splash of super-plasticizer making up the rest.

Today, finding that the slurry seemed "pretty hard" I went ahead and finished the polishing. Results attached below. Experiment #1 is the clean looking one. I'm starting to get skeptical that this will work for countertops, but I'm learning a lot.

What I've learned:

• When grinding, make sure *everything* is more or less smoothed out, or else the slurry will fill it.
• Don't put too much slurry on--I had to back up to 100 and 200 grit pads to actually uncover the black areas. This of course exposed new bugholes
• Pouring face up seems to work out just fine, in priciple. The edges got ground away, and the finished surface was plenty smooth.
• If I put a dark slurry on to patch bugholes, I need to actually let it set before adding the light slurry (that's why I ended up with a cookies and cream look in places).
• Either the thick layer of slurry in the indentations cannot be polished smooth, or it needs more the 24 hours to cure before it can be polished.

So, for #3, assuming that the mat didn't come loose when I vibrated the form and is impossible to get out, I think I will grind after 6 days, then fill holes with dark slurry, then wait a day, then add light slurry, keeping as thin a layer as possible on the raised areas, and then wait several days before finishing the polishing process.

[david s]

Re: 36" Pompeii in DC

Thanks for sharing your experiments. I was down at our local hardware shop (Bunnings) to purchase an item and while browsing noticed the exact same rubber mat. Had to buy it of course. I walked out with 5 items. This always seems to happen to me. When time permits I hope to make some castings with it. Thanks.

[Gulf]

Re: 36" Pompeii in DC

I'm enjoying this experiment very much. I love what you are trying to do and with the spirit of this forum I/we are learning from it . The mat idea is original and worth pursuing. This just a suggestion, one that I would/will try if you don't.

My brother did a feauxe stone concrete sidewalk once by using the old Quikcrete walk maker form. What he did was use the form as a stamp for the surface rather than as a form.

Try placing very thin plastic between your mat and the pour. In an upside down pour (the press method), the concrete would have to be fairly firm as is suggested. It would have to be pressed firmly into place.

The plastic should be the type that they make laundry bags from. I have bought some cheap drop cloths from the dollar store which are a similar thickness.

For the stamp method: cut a plywood board the size of your form. With the plastic on top of the fresh concrete, set your mat. Place the board on top of the mat and tap down lightly with a hammer or rubber mallet.

Leave the plastic in place until Simi cured.

Hope this helps.

[TropicalCoasting]

Re: 36" Pompeii in DC

To add another twist to the experiment have you thought of adding broken glass ?

http://www.heringinternational.com/i...Beton6_480.jpg
it looks fantastic.

[fabby]

Re: 36" Pompeii in DC

thats a pretty cool build, thanks for sharing all your techniques. I enjoyed the read.
Where did you find the insulating board at? I am in Richmond and cannot find a supplier. It looks like I will order from Mcgills here soon.
thanks.

[rsandler]

Re: 36" Pompeii in DC

thats a pretty cool build, thanks for sharing all your techniques. I enjoyed the read.
Where did you find the insulating board at? I am in Richmond and cannot find a supplier. It looks like I will order from Mcgills here soon.
thanks.

I got my insulating board from Distribution International. They seem to have a Richmond location. In DC, the local warehouses didn't have any in stock, but even with a $30 freight charge to ship some in it was cheap. I seem to recall that Harbison Walker has a location somewhat near you as well (though it would have been a schlep for me). Look for a local boiler repair place as well--I got my blanket from one such and could have gotten insulating board for a little more than I paid for the Distribution International product.

[rsandler]

Re: 36" Pompeii in DC

Question(s) for folks:

We get enough rain on a regular enough basis here that the high-lime render just isn't cutting it to keep moisture out of the insulation. I don't have enough space on my stand to change plans and go for an enclosure (and I still want to do a tile mosaic), so I think I need to apply a water-proofer of some kind. From elsewhere on the forum, I know that if I do this, I ought to drill a hole in the top for ventilation and put some kind of rain cap on it.

The questions: What do I drill this hole with? What sort of a thing do I use as a rain cap (that is, when I walk into my local hardware store, what to I ask for)? Will waterproofing the stucco cause problems with getting tiles to stick once we get around to doing the mosaic?

[david s]

Re: 36" Pompeii in DC

You really need a core drill like the type guys who install split system air cons use, but you may be able to get away with using a normal cheap hole saw (it won't be much good after) as the lime render is not too hard. If that douesn't work a series of small holes in a circle with a normal masonry bit will do but will leave a ragged finish. I suggest you make up your own cover with whatever you can find.

If you water proof before tiling, yes you may create a problem with the tiles adhering, I think it would be better to add a waterproofer to the tile grout.

[rsandler]

Re: 36" Pompeii in DC

You really need a core drill like the type guys who install split system air cons use, but you may be able to get away with using a normal cheap hole saw (it won't be much good after) as the lime render is not too hard. If that douesn't work a series of small holes in a circle with a normal masonry bit will do but will leave a ragged finish. I suggest you make up your own cover with whatever you can find.

If you water proof before tiling, yes you may create a problem with the tiles adhering, I think it would be better to add a waterproofer to the tile grout.

Thanks, that's really helpful. I had figured on waterproofing the tile rather than the stucco, but for various reasons the tile finish is rather far down my list of projects. Certainly won't get to it until summer, maybe won't get to it this year at all. In the meantime my insulation keeps getting wet. Hmm. I think the answer may be to come up with a semi-permanent cover. Something easier to take up and down than a tarp (and hopefully a smidge more attractive).

I feel like where I really went wrong here is the point where I managed to eat up most of the 8" of clearance on the sides of my oven with 3 layers of blanket, and instead of taking it off and re-doing it to make room for the steel studs of an enclosure, I decided to punt and go for an igloo finish. :P I do really like the tile mosaic idea that is the current plan, but if the ceramic blanket wasn't so expensive I'd be pretty tempted to break off the render and start over.

[V-wiz]

Re: 36" Pompeii in DC

How about a semi enclosure . Add 4 posts and a roof, dont close off the dome, just add a roof.

[rsandler]

Re: 36" Pompeii in DC

How about a semi enclosure . Add 4 posts and a roof, dont close off the dome, just add a roof.

Mostly because I've got to finish the dome with something (my stucco job is too rough), and the oven is back up to our raised deck. If I'm going through the effort to put a tile (or other) finish on the dome, I want to be able to see it from the deck. I'm not crazy about the semi-enclosed look, in general (all due respect to Gulf and others for whom that was the preferred look).

That said, if keeping rain off the insulation becomes enough of a problem, I may well go that route!