#11  
Old 02-26-2011, 04:24 AM
Peasant
 
Join Date: Jan 2011
Location: Canada/Tanzania
Posts: 39
Default Re: Tanzania/Canada

Thanks Dave,

Thanks for the continued encouragement.

The formula that I am using is a slightly modified fireclay mix which is in the plans (1-portland cement, 1-lime, 1-fireclay, 3-sand). In my testing I tried to use ground down soft clay bricks that are made here for the fire clay and didn't feel comfortable with the results. I thought the use of termite mud gave me better results.

Mind you, the testing proceedure was pretty rudimentary!...making pucks out of different mixtures and roasting them on a grate over a wood fire. Not exactly a proper cure of the mortar before the high heat! I can only hope that I made the right choice. Time will tell!

In any event the termite mud that I get from the brick man is already processed by being sieved, premixed 4 parts termite and one part sand and let to stand for quite some time. By the time I get it the mix is moist and I think it has been passed through the brick making machine(large meet grinder) once and let to stand again under cover for a time. When he makes his final bricks he uses this material. The bricks are fired at about 900 degrees for about a month using smoldering rice husks. They come out amazingly hard.

I have a bucket of this mud which is moist and about as sticky as you can imagine. So what I do is take 5 cups of mud (premixed at 4-mud and 1-sand),
11 cups sieved sand, 4 cups lime, and 3.5 cups cement. That gives me the 3-1-1-1 mix being a touch light on the cement.

I will let you know how things go with the curing.

Sorry about the pictures in these posts. I have registered this site with imageshack and for a while the images were ok and now were back to the frog in the icecube and you have to click on that....at least that is what I'm seeing.

Cheers SteveS.
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  #12  
Old 02-26-2011, 11:23 PM
cobblerdave's Avatar
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Location: brisbane australia
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Default Re: Tanzania/Canada

SteveS
Pics are good so don't worry. Your works looking very neat especially considering you doing the brick cuts with an angle grinder!!! I recon it will be a little harder now you'll have cut the brick size down as the curve at the top gets "tighter"
Any thoughts on the insulation layer over the dome your using a local plumice mix arn't you?
Thanks for the info on the "Tanzania Home brew mortar". Thought it would give a good mix because after the termites digest the stuff the only thing left is clay and sand any thing of an organic nature is long gone. Nothing will grow in it... thats why it used to make tennis courts in the bush I recon.
The drips of home brew mortar that I found after I had burnt out the ply brace that supported my oven construction were still hard but a bit lighter than just the normally dried mortar lumps. Recon the heat broke down the cement leaving the clay lime and sand. You samples turn out the same way?

Regards Dave
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  #13  
Old 02-27-2011, 07:39 AM
Peasant
 
Join Date: Jan 2011
Location: Canada/Tanzania
Posts: 39
Default Re: Tanzania/Canada

Yes Dave, I am planning on covering the exterior with the pumice stone cement mixture.
Since I don't have a thick layer of refractory over the bricks (infact the soldier coarse has none) is it okay to just use regular cement sand mixture with the pumice for insulation?

Cheers, SteveS.

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  #14  
Old 02-27-2011, 12:37 PM
cobblerdave's Avatar
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Default Re: Tanzania/Canada

Dear StevS
Cant see why not. Don't know how you "mix' will act... might be hard to trowl?
You might have to consider a cage of wire to contain it till it dries but which ever way go for a good 4 inches thick. can't think of anything else which could be of use....

Regards Dave
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  #15  
Old 02-27-2011, 05:29 PM
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Default Re: Tanzania/Canada

Why sand? Just use a 5 to 1 pumice/cement. That's what I did, works fine. just don't add too much water. Make it a dough like consistency and just trowel it on in big chunks. You can make it what ever shape you want.
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  #16  
Old 02-28-2011, 12:40 AM
Peasant
 
Join Date: Jan 2011
Location: Canada/Tanzania
Posts: 39
Default Re: Tanzania/Canada

Thanks lwood! I will try that for sure. It will be much easier and faster. Just a quick question though. Since I don't have a coating of poor mans mortar around the outside of the soldier coarse do I have to worry about too much heat from the back side of the bricks breaking down the insulation layer?

Cheers SteveS.
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  #17  
Old 02-28-2011, 04:03 AM
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Default Re: Tanzania/Canada

If you add sand to your insulating mix it will make it stronger, but will also reduce its insulating value because you are filing lots of the air spaces between the pumice with the sand. The purpose of the cement is just to hold the pumice in place so you can stucco over it. Degradation of the cement in the insulating layer doesn't matter once it's in place.
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  #18  
Old 02-28-2011, 01:01 PM
Peasant
 
Join Date: Jan 2011
Location: Canada/Tanzania
Posts: 39
Default Re: Tanzania/Canada

Just thought that I would share a picture of the application of the lower level of the pumice cement insulation. Used the 5-1 ratio. Thanks lwood. Seems to be setting up just fine. Hope to finish the dome tomorrow.

Cheers SteveS.

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  #19  
Old 03-02-2011, 03:01 AM
Peasant
 
Join Date: Jan 2011
Location: Canada/Tanzania
Posts: 39
Default Re: Tanzania/Canada

Hello All,

Pumice insulation application is now complete. Thanks for advice on the mix lwood...worked well. Stucco application next...never done this before either. Any advice anyone? How thick?(both rough coat and finish coat or just one coat), what type of finish is better...smooth or textured?...paint?

Any quick advice will be greatly appreciated!

Cheers SteveS.

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  #20  
Old 03-02-2011, 12:40 PM
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Default Re: Tanzania/Canada

SteveS
Here's a Mugs version of Render
The art is to started at the bottom get some mix on your steel float and Push the mix on Up and the the right or left at angle of 45 or so. you can then smooth it of. Remember Push the mortar on and it will stick. Check the pics out and your finish looked alright on the dome but did you play with the mortar with you hands?... we all do I think.
Don't know whats avaliable in Africa as a seal coat at a pinch you could try a flat plastic paint. I say Flat not Gloss as a gloss shows up all the lumps and bumps.... flat is more forgiving and gives you a softer finish
Hope something here helps

Regards Dave
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