Lime mortar & wood ovens?

[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..

[david s]

Re: Lime mortar &amp; 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.

[brickie in oz]

Re: Lime mortar &amp; 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 &amp; 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 &amp; 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 &amp; 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.

[KraemerBAC]

Re: Lime mortar &amp; wood ovens?

Very interesting thread and quite a bit of "food for thought"

Thank you everyone

Peter

[adam2]

Re: Lime mortar &amp; wood ovens?

I wouldn't. The thing is, once a brick is broken its 'innards' are exposed. Although brick is fired, the interior is usually much softer. Lacking the external shell, the interior wears much faster*.

Much older brick will be harder inside - longer hardening time (like concrete, brick continues to set up long after being fired - it's just much slower) - but no brick is ever as strong once broken. You can reuse them for a variety of things, but a fireplace undergoes some pretty extreme temperature changes which have been known to crack full brick - a broken brick is not likely to take it well.

Conversely, brick in brick ovens are often cut. But most are also firebrick which is better suited to oven conditions.


*I'm going by what I've read on the subject. It's not something I've read extensively about so don't take it as gospel. I think it's correct or I wouldn't mention it but I'm not as sure about this as I am about other topics I've read more about.

Thanks for the helpful advice, but since my last post, I went ahead and made the wall out of the broken brick. It looks rustic, but fine for outdoors.

I forgot to mention there already is firebrick lining the interior, this brick is outside of it, I guess mostly for structural support and looks.It is just a firepit for casual after dinner fires. I use it maybe twice a summer.

[brickie in oz]

Re: Lime mortar &amp; wood ovens?

Where are the real life examples?
And net examples?

Here are some bad repairs using cement based mortars.

[dmun]

Re: Lime mortar &amp; wood ovens?

Here's a link to a Penna. based lime mortar manufacturer, much good info on site:

Lime Works.US

[Tscarborough]

Re: Lime mortar &amp; wood ovens?

The reason the brick broke is because the portland cement based mortar is harder than the brick. Any stress is thus relieved through the brick instead of the mortar. You can reuse the brick, but the rule of thumb is that no piece should be less than 1/4 of a whole unit.

FYI, there are no structural advantages to using portland cement mortar. It has advantages in initial set and moisture resistance, but ultimate strength does not apply outside of highly engineered masonry structures.

[Archena]

Re: Lime mortar &amp; wood ovens?

I wouldn't. The thing is, once a brick is broken its 'innards' are exposed. Although brick is fired, the interior is usually much softer. Lacking the external shell, the interior wears much faster*.

Much older brick will be harder inside - longer hardening time (like concrete, brick continues to set up long after being fired - it's just much slower) - but no brick is ever as strong once broken. You can reuse them for a variety of things, but a fireplace undergoes some pretty extreme temperature changes which have been known to crack full brick - a broken brick is not likely to take it well.

Conversely, brick in brick ovens are often cut. But most are also firebrick which is better suited to oven conditions.


*I'm going by what I've read on the subject. It's not something I've read extensively about so don't take it as gospel. I think it's correct or I wouldn't mention it but I'm not as sure about this as I am about other topics I've read more about.

[adam2]

Re: Lime mortar &amp; wood ovens?

Oh yeah, the whole reason I joined this forum is because I had a question about rebuilding a brick fireplace out of broken bricks. Anyone have any advice? I was going to reuse any bricks that are broken in 2 (or maybe 3) but the smaller pieces I was going to set aside.

For those interested, the whole reason the bricks were broken and in many cases completely in shards is because the previous owner used quickrete with bricks. Over the past few years the quickrete has separated from the bricks due to moisture.

I'll be using a lime mortar to ensure good adhesion and longevity for the fireplace. I am also probably going to use a pure lime/sand/water mix. The fireplace is only 4 feet tall so it does not require any of the structural advantages of using portland cement.

[adam2]

Re: Lime mortar &amp; wood ovens?

I own a home in Hamilton Ontario built in the 1880's. The entire house is made of lime-based mortar of that era. The brickwork is all original and still in impeccable condition. it is a 2 1/2 storey home. Over the past couple years I have been using lime mortar with great success to repoint the basement.

A bit about the brickwork:
~~~~~~~~~~~~~~~
A structural engineer inspected the house and said she has seen homes that are 10 years old with brickwork in worse condition! All the bricks are perfectly level and the only damage is in an area where they failed to put up proper eavestrophes and dripping water has eroded the brick over the decades.

The basement is stone and needed repointing last year. I hired a couple of masons with experience working on old churches and cathedrals in England and they educated me in the lime mortar. I also learned how to properly mix, apply and finish mortar to joints. Needless to say, the original structure was built with lime mortar and lasted 130 years, and I was told their repointing work should last another 40-50 years. The stonework is now done and absolutely beautiful.

A bit about concrete repair:
~~~~~~~~~~~~~~~~
As mentioned before the house was built in the 1880's, and there have been many previous owners. Over the decades, it is evident parts were patched with concrete. In all of these areas, moisture has built up around the concrete but had nowhere to go since concrete is impermeable so the water has pushed the concrete out and separated from the stone. In some cases it took parts of the stone with it and produced spalding. The concrete has been chipped away in these areas and repointed with lime mortar. Another interesting thing I learned was the "healing" properties of lime mortar. When cracks develop, they end up sealing themselves from moisture pushing up against the lime joints. Any gaps get filled in with lime from the mortar due to moisture that seeps around the joints (this is a perfectly normal situation with lime mortar). Again, this type of joint has lasted thousands of years in many buildlings in europe (including all buildings of historical interest in Italy).

What brought me to this forum was my outdoor brick fireplace that was there when I purchased the home. It is obvious all the joints are made from quickcrete. The bricks are all spalding and splitting. I just recently noticed that as of this summer NONE of the bricks are adhered to the concrete joints. This isn't surprising - as I stated before - the moisture gets in between the brick and the concrete and pushes against the concrete and separates - this is the risk of using concrete with bricks exposed to any moisture).

The conclusion that I draw is that quickrete or pure concrete is an absolutely horrible thing to use for joints of bricks with any porousness. Lime mortar is an excellent medium to use for joints between stone and brick. The lime mortar is the sacrificial material - you NEVER want the brick to be the sacrificial material because then your structure will fall down. mortar can be repointed a lot easier than replacing all the bricks.

[jpmort]

Re: Lime mortar &amp; wood ovens?

I am considering making my low dome pizza oven from clay, some red bricks, and lime mortar. I wonder if there is any feedback from those who have used this material? I understand that homemade ovens in Italy use lime mortar because it is able to be less brittle than concrete, and therfore does not crack in the same way.

I am also interested in how how a temperature the lime mortar can withstand, and if I need to mix in anything in with it to make it withstand 450C degrees?

Many thanks,

John