Lime mortar & wood ovens?

[david s]

Re: Lime mortar & wood ovens?

Only just discovered this thread. Two points Firstly never mix lime with calcium aluminate cement.It simply acts as an accelerant and makes the brew "go off" faster than it's already rapid setting rate. Secondly, the carbon in the wood we burn is carbon that is already in the system. We are not adding extra carbon like when fossil fuels are burnt. Sorry these remarks relate to comments very early in this thread.

[brickie in oz]

Re: Lime mortar & wood ovens?

never mix lime with calcium aluminate cement.It simply acts as an accelerant and makes the brew "go off" faster than it's already rapid setting rate.

Rubbish.
Lime has the ability to keep cement based mortar workable for longer especially on hot windy days, the hotter it is the more lime you add to your mix.

[david s]

Re: Lime mortar & wood ovens?

Read my post bricky. I said lime and CALCIUM ALUMINATE cement are a bad mix. Lime and Portland are compatible.

[brickie in oz]

Re: Lime mortar & wood ovens?

Read my post bricky. I said lime and CALCIUM ALUMINATE cement are a bad mix. Lime and Portland are compatible.

So why did you add lime to fire cement? I presume thats how you found out?
I dont get it, no one would add lime to fire cement.

[david s]

Re: Lime mortar & wood ovens?

Because calcium aluminate cement and lime are both refractory materials and I was attempting to create a cheaper brew. I do a lot of experimenting with different materials. Actually the Forno Bravo has a recipe also that quite incorrectly suggests using these two materials in combination.

[silverman]

Re: Lime mortar & wood ovens?

[QUOTE=TrevorML;15870]Seriously Dave... chill...

all I am doing with this post is for my own information... and those that are interested... in the use of pure lime mortar for building an oven...


Over in Yahoo Groups, there is a bright "brickie" fellow that uses lime putty for building..
I copied a post from him a while back regarding lime putty.. I'm reposting it here FYI.. I dont have this experience of building with lime putty, he does, I am just reposting this because of the interest generated, and my own interest in using lime for my oven.

** Re-post below**

Hi ya'll, in Pa we have Lehigh brands, a division of the Heidleberg Cement Global,
who bought them out a decade or so ago.
Nevertheless, their Lehigh White 'N' Masonry Cement is very close to a refractory,
since it contains such a low content of the ferrous compounds,
that makes standard grey portland unable to stand continuous, repeated temps above 800+ degrees.

SO, the recipe is...
3 parts lime putty (simply buy the bag of hydrated lime,
and taking (2) 5 gallon buckets with 1/3 water in each,
slowly dump the lime powder divided evenly between the two.

It will be near the top, but, will wet and then take your slow (0-750rpm) drill motor and starting slooowwly
...mix the two parts of each bucket, till you get a soft 'peanut butter' consistency...
adding only part of another quart of water to each..as necessary..as you go.

DO NOT OVER WATER...then, you simply have a 'lime wash'..NOT..what you want.
After sitting at least a week, covered to prevent drying, you can use this 'lime putty'.

BUT, to get a 'set', you need to use the above-mentioned Lehigh White N Cement (NOT..!..portland..).

THAT recipe is to evaluate what you need in the next 12 hours,
and proportionalize the equivalent of (1) part wetted (again..) Lehigh white cement,
of 1/3 to 1/2 max the lime putty needed to make a 1/1 ratio of final product,
the final product being ...(taa..daa..!)..
1/1 ratio of 'mixed' lime/cement 'binder' equaling (1) one part, to the >combined< (1) one part of 'binder'.
NO CLAY..!

Now, under practical testing of repeated cycles of firing a full arched (IE hemispherical/pompeii oven) oven,
the dome above the fire being upwards of 1,150F (the IR thermometer topped out..!)
this mix has performed well.

This is also, minus the clay, very close to a mix used by Pennsylvania Germans in their
brick bake ovens of 2 centuries ago.

Now, clay maybe added, as the above recipe, would have used 'low fired',
locally burnt lime, and sometimes clay, sometimes more, or, less sand.
I have found one 140+yr old oven, still intact with small joints,

and what I scratched out seems to be just lime putty, as I could detect no sandy particles in it.
(that was with a crude test of taking a pencil eraser sized part and slowing crumbling
it between my teeth, swishing around the front of my mouth,

so that your tongue pressing it against the back of the front teeth caused it to re-hydrate
with saliva into a slightly sticky mass, I presumed lack of clay, for the clays around that
locale always have a sand/particulate component.

Now, you have to sample a lot of mortars in this way, as I have to get a 'handle' on their respective 'stickiness',
'gritty-ness', and rough proportion of content....short of acutual lab/microscopic testing..!)

** end repost**

Cheers..