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Re: Woodchip Clay Brick [Re: D L Bahler] #24264 08/22/10 06:26 PM
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Cecile en Don Wa Offline
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Here is a clay block wall in a workshop I built some years back, as a sort of limited illustration for the topic as there were no timbers involved in the wall construction.

The blocks are compressed clay with a fairly corse agrigate - up to roughly 4 mm- of river sand and hemp or flax (once the fibers from the dried plant stocks are removed, this by-product is left over, lets say the shredded outsides of the stems. I made a pile the other day with my daughter when we were making rope).

The mortar is more or less the same stuff the blocks are made of - even breaking up and using the blocks themselves is ideal because as mentioned, the mortar has a certian relationship to the brick/block used and should not just be arbitraily chosen.

I understand the idea about using woodchips as a filler and I'm sure it has been done but I am sceptical about using it for this purpose. Wood chips don't seem like a very stable medium and wood shavings seem rather useless because the fibers are all shorn through. It takes me more effort to pull apart a stem of flax or even a piece of straw then it does a shaving of wood and wood chips and shavings attract moisture. So there are no structural advantages to wood and what's more they may weaken the structure. As for the insulating value of wood we all know that it is a shitty insulator whereas straw is not bad and hemp and flax are very good insulators particularly regarding sound insulation. I've just never heard of anyone who regularly works with clay and has easy access to wood chips and shavings using them in combination. For many of the same reasons I don't dispose of my wood chips and shavings by using them in the stall or chicken coop I wouldn't use them in the clay. Wood chips are better destined for smoking your ham or covering your path.

Re: Woodchip Clay Brick #24265 08/22/10 06:55 PM
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D L Bahler Offline OP
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I am sitting here thinking of this idea of bricks... What other materials could conceivably be used to make infill bricks

What I mean here by an infill brick is a brick or block of some sort that has a relatively high insulating value that is intended to be used in the space between framing members, and does not necessarily have any structural strength of its own -not something that has to be able to support a roof structure in other words.

Perhaps a bit of historical reflection would be in order here...
In the Middle Ages, Europeans devised a number of methods of infilling their timber structures. Just about everybody came up with wattle and daub.


Bricks were also used later on, particularly those bricks that were of inferior quality and so w=could just be tucked away somewhere inside a wall and covered up.


Since the days of the first Viking settlements, Icelanders built timber framed houses that were infilled and enclosed with huge turf walls several feet thick


Medieval Scandinavians built Stavverk buildings, such as the great Stave Churches that one could say employed a wood infill, as the boarding on these buildings are placed between the framing timbers, not on the outside.


Central Europeans used at times a similar system


This occupies a strange gray area somewhere between infilled timber frames, boarded frames, and log building.

Other techniques used in the past include Stone infill, mud bricks, and so forth.

In the 1960's and 70's, Germans were faced with the prospect of repairing a large number of half timber buildings that had been damaged during the war, and patched with temporary and inferior methods afterward. This sparked a revival in traditional methods, and also great innovation. It is from this that the light clay infill methods developed.

Now I am thinking of straw and wood chip blocks in terms of blocks of rigid insulating material stacked between timbers. Thinking on those terms, I wonder what other materials might be usable in a similar sense, particular natural materials or waste products.

So I have thought of a few materials that might possibly be made into bricks:
Cellulose
Charcoal
bast fibers
Cambium, or inner bark, of certain trees
sawdust, as opposed to woodchips
tire shreds

All of these would be used in conjunction with some type of binding agent that would also inhibit burning, and most would also require something that would protect against insects. Things like clay, lime, or cement (remember, there are types of cement other than portland)

Of these, I know a bit about the thermal properties of charcoal.
Charcoal is produced by forcing volatile chemicals out of wood, leaving behind almost pure carbon. In the process of forcing out the chemicals and leaving behind carbon, a lot of 'extra' space is left. The piece of coal is about 60 to 75% the volume of the piece of wood it once was, but only 20-30% the weight. That means it is now mostly air. You can tell this when you pick up a chunk of charcoal because it is very light relative to its size.
To make charcoal you have to heat wood up to at least 500 degrees fahrenheit, and the finished coal can retain this temperature for hours or even days after it is removed from the kiln. In addition to this, you can be holding a piece of coal in you bare hand while it is flaming red hot just a few inches away and not be the least bit uncomfortable.
It does tend to put off a very fine dust, and it is also really flammable. But I think that enclosed in clay both of these problems could be dealt with (straw for example can have both of the same problems. If you don't believe me, try working in the loft of a barn where straw has been stored. It's very dusty) I have seen already where a trailer load of straw from the field spontaneously erupted into flames because of the heat produced by the stacked bails as they dried. I have also seen barns burn down for the same reason (and I have seen grain bins explode when being loaded with soy beans when the bean dust ignited from friction or static electricity)

Last edited by D L Bahler; 08/22/10 06:56 PM.

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Re: Woodchip Clay Brick #24294 08/25/10 05:27 PM
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Wow great post.

I've been thinking about this too. I haven't liked clay bricks or straw/clay, or adobe or rammed earth for us here in the NW because low R value and maybe not so good in the rain (not to mention earthquakes). However, in keeping with my desire to use local materials, I've been thinking about pumice. There is a lot of this red pumice mined around here for gravel roads. It's full of air, it's light weight, combine it with cement and you have a strong light weight warm wall, yes? I believe there is a man in NM doing something like this:

http://www.pumicecrete.com/Hybrid-Building-Applications.htm

Re: Woodchip Clay Brick #24298 08/26/10 05:23 PM
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I read somewhere that this infill methods will have approximately r-2 per inch of thickness, compared to Owens Corning rigid foam insulation which has r-5 per inch.

Here's some r-values fro comparison:
Extruded polystyrene 5.00 per inch
Expanded polystyrene 4.00 per inch
Polyisocyanurate & Polyurethane 6-7 per inch
Blown in Cellulose 3.70 per inch
Fiberglass Insulation 3.14 per inch

compared to the estimated 2 per inch of a light clay infill.

However, R-value alone doesn't tell you the whole story. Clay also acts as a thermal regulator, meaning it holds on to heat. That means that heating systems don't have to run as much to keep a building in a comfortable temperature range. However, a light clay system likely won't do this enough to be of much consequence.

One thing about charcoal that I did not mention earlier that could be a possible drawback is that it is highly absorbent. However, charcoal will absorb a certain amount of chemical and then simply stop absorbing. To my knowledge, it does not then diffuse those chemicals into the air later. It likes to hold on to them. Which might actually be a good thing, the wall might absorbe the various toxins that are floating around in a home when it is first built such as paint and glue solvents, and so forth.

This weekend I plan on making some experimental bricks out of a variety of materials such as Charcoal, Wood chips and shavings, straw, and maybe waste paper. I also plan on subjecting them to a number of tests once they are dry, like testing their fire resistance, conductivity (not very scientifically though) and how well they hold up to water. I'll post my results when I have them.


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Re: Woodchip Clay Brick #24300 08/27/10 01:06 AM
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Here a some pictures of my experiment.

I made some bricks using clay and charcoal, and experimented with different ratios of clay and coals.

I have decided that it works best if you have a really wet slip, as it mixes in with the coals much better. Too thick and the clay tends to get stuck to a small clump of coals and won't mix in very easily. Too thin, however, and it will be too weak.

You can see in my picture of the formed up bricks where I changed the mixture a few times. It is better to have a little too much clay than not quite enough of clay, because if you do not have enough it is far too difficult to get the bricks out of the form without them crumbling.

Sloppy slip

real wood charcoal, made in my own kiln[

Smaller pieces work best, which is good because they aren't useful for other the things that I use my charcoal for!

The mix

the form, a little oil on the sides helps the bricks to come out easier

lets make some bricks! A small batch of 25 bricks made for test purposes.


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Re: Woodchip Clay Brick [Re: D L Bahler] #24312 08/29/10 04:28 PM
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Cecile en Don Wa Offline
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Hi,
regarding clay in general, you must distinguish between different compositions in relation to its use as a building material. Maybe these distinctions will come back in America if this material were to become more generally used again. In England what is commonly used in relation to building is called, loam, (here called leem). This is a clay based material, containing aggregates for binding, (clay is the binder but a binder must necessarily have something to which to bind), strength and stability. Sometimes fillers are added for insulation, weight reduction, increased mass or structural advantage.

The only use for more or less pure clay, which is the inert remains of what was once organic material, in relation to building would be in the form of a sort of rammed earthen floor - unless you want to include baked tiles. Even these floors were traditionally stabilized. First of all, like Tim Beal writes there, by letting the natural clay stand under protection out doors for minimal 1 year - better three - to degrade imbedded organic material and break down it's inherent structure, and then further with the addition of horse urine and/or old beer, adding lime to increase hardness.

These floors can be adopted even for modern housing but in my opinion are better suited for barns, stalls, workshops. There is no better floor than this for a blacksmith's workshop, being fire and shock proof.

That said, there is this clay floor and there are composite clay, (in American terms), floors. That just means the material has been adapted to whatever particular conditions call for where it is used. And if I were to claim to be making a point at this point it would be that the uses of clay in making buildings are pretty limited. If I were to add anything practical that would be that a person can come to some conclusions about the ground under his or her feet with a simple test. Put some ground in a clear glass jar, let it settle, and it's possible to see its composition and their ratios to each other as the various components separate into layers .

Don Wagstaff

Re: Woodchip Clay Brick #24315 08/29/10 05:17 PM
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Soil is a general classification of various amounts of primarily Clay, Sand, and Silt. These three materials are essentially the same thing broken down to varying degrees, which are various mineral crystals that vary by region. Certain minerals break down easier and so are more likely to be in clay (lending clay its unique properties) while others (such as quartz) don't break down as easily and are more likely to compose sand. Thus native minerals will determine your soil type, its ratio of sand clay and silt.

Soil can contain suspended amounts of decayed organic matter such as peat. But peat itself or other organic materials are not a true soil. Organic materials suspended in soil are beneficial to farming, and it is the suspended particles that contain the nutrients needed to grow plants. The soil itself primarily affects drainage characteristics.

Loam is a mixture in varying degrees of Clay, sand, and silt. A medium loam has nearly even mixtures of the three. Loam therefore contains aggregate and binder premixed for you, so it is tremendously useful.

in Indiana a we have a topsoil that is a medium loam of some sort, with an subsoil that is clay, the deeper you go the purer the clay. The topsoil can vary over a very small area from a high clay loam (especially on 'clay knobs") to a silty loam, to a sandy loam in lower areas.

If you are to mix in straw, than you should search for a high clay loam. You can use straight clay, but you might want to mix in some sand as an aggregate. Even fired clay bricks must contain aggregate for stability. Modern bricks are 50% clay and 50% ground shale. Older bricks were made of soft clay with at least 25% sand.

-This knowledge of soils comes from growing up in a life where the soil is very important, and so knowing the soil is important.

For my bricks, as an example, a very high concentration of clay was desirable. That is because I have an aggregate already present, charcoal. So I need primarily a binder. A small amount of sand is good but not vital. I do not want a good loam because it would not be 'sticky' enough or strong enough.

By introducing lime, you are increasing the calcium content. we do this all the time on our fields because we have acidic soil (because our land was mostly peat bog 100 years ago) Calcium hardens the soil, which is why we use it for walls, and if you have a loam of a neutral pH then it will kill microorganisms. In acidic loam it will actually encourage microorganism growth which is one of the reasons we use it for farming. microorganisms are a vital part of the life cycle of a plant, but not as vital in your wall.

here is a handy diagram from Wikipedia showing the soil types and how the relate.


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Re: Woodchip Clay Brick [Re: D L Bahler] #24316 08/29/10 06:58 PM
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Hi D L,
you are right to point out that these characteristics can also be inherent and are not necessarily a product of any particular recipe.

You call your charcoal, (an interesting idea), an aggregate, comparable to sand, crushed seashell or gravel.... Why not a filler in the category of straw or flax...?

Here is what I have found are some of the working properties.
Too much sand and there will be no strength.
Not enough sand and cracks will develop.
Too much water and there will be excessive shrinkage.
Too little water and the mixture will dry out overly fast and not harden or adhere properly.
Mineral additives, namely vermiculite or too much lime in my experience, weaken the bond of the clay.
Albumen, egg white, casein, are examples, increases the fastness once it has dried, that is it will not give off dust when you rub it so much.

It will be interesting to hear how your bricks come out when dried.

Don Wagstaff

Re: Woodchip Clay Brick #24317 08/29/10 10:12 PM
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The biggest problem I had using the clay subsoil was that our red clay is very dense and fine-particled. This means that when you start to mix it with water, the clay will absorb a certain amount of water and then proceed to clump together. I experimented to see if this could be avoided, and it made no difference whether I first ground the clay into a fine powder or just threw in large lumps. So it took quite a bit of effort to get it to mix evenly without too many lumps. In the future I need to use a method other than hand-kneading as this take a very long time.


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Re: Woodchip Clay Brick #24319 08/30/10 09:46 AM
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