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Revision as of 07:57, 10 May 2008

Template:305inprogress

Description

This project is an exploration of compressed earth bricks. Mostly because they're awesome.

Opportunity

CCAT, the campus center for appropriate technology, has recently relocated and their new grounds have many uncontrolled hillsides. With general erosion problems and hazards posed by downhill water flow over clay, the need for retaining walls is immediate.

Literature Review

Compressed Earth Brick (CEB) basics

Compressed earth bricks are building blocks formed from stabilized or un-stabilized compressed earth. The compression ranges from several hundred pounds total, to several tons. Because of the great gains in durability un-stabilized bricks are only used where nothing is available to stabilize the bricks. In addition to stabilization, the earth the bricks are to be made from is calibrated for durability, workability, and survivability.

When a brick is compressed it looses 30% of its volume. This is due to the mechanical compression of the press driving out air pockets and aligning wet clay particles and compacting the clay around the sand particles.(http://www.networkearth.org/naturalbuilding/ceb.html)


Stabilization

There are many stabilizers that can be used. They can be broadly classed into natural and manufactured. They include such wondrous things as plant juices, whey, resins, molasses, wood ashes, and lime just to name a very few. Here in the United States, the presence and low cost of cement makes it both physically and economically efficient( App. Bldg. Mat. p.33, Bldg. Mat. Dev. Co. p.33). Some sources don't even recommend using stabilizers other than cement even when building in developing countries()


Paper as a stabilizer

Papercrete, a cement and paper building material, has been fairly well researched and tested.(http://www.livinginpaper.com/mixes.htm) The paper in papercrete is proported to have great effect as a stabilizer. Amongst the problems with papercrete are, mold, shrinkage, and slow drying time.(http://www.greenhomebuilding.com/articles/papercrete.htm) ( App. Bldg. Mat. p.33, Bldg. Mat. Dev. Co. p.85)

Criteria

critirion personal project adjusted success
Teamwork 7 | .5
7 | 7 | 1
10 | 10 | .8
2 | 6 | .5
4 | 1 | .8
10 | 10 | .8
10 | 10 | 1

Project goals,

research, practical testing, education, team work, experimentation documentation



research,

The research has been the most challenging part of this project. Most of the information I've been able to find is out dated. Most of the people holding real practical current knowledge are companies that are in the business of selling some sort of product. I hope that the work I've done here encourages more people to do practical and experimental work and document it for the general public.

practical testing,

The practical experience of using a CINVA-ram to make bricks reveals that it is quite a bit of work. The physical process of harvesting, sorting, mixing, and, pressing a brick, is, in the end, a lot of work.

Not including set up and strike, I would estimate that I average 9

bricks an hour, at best. The real average, all time included, lands around 3 bricks an hour. Though experience and good teamwork will do amazing things to these numbers, this process does no seem to make financial sense in the current American economic climate.

education,

I got to teach about two dozen people how to make bricks with the press. Additionally, about another two dozen received peripheral exposure to the technology. I was also able to enter one of the bricks in a sculpture show at Muddy's Hot Cup, under the umbrella of art another hundred some odd people have gained exposure.

team work,

Though I think many of my classmates may have resented my chastising harshness, fun was had by many. Shenanigans were even present at one point and I learned a valuable lesson about hose control when using the hose as a motivational tool. Overall the experience was a great one for a team, it seemed that about 4 to 15 people could have a good time making bricks in the sun for half a day.


experimentation

My work with integrating paper went marvelously. The addition of 2 percent paper by weight allowed for the reduction of cement from 10% to 5% with no apparent change in brick strength. This is as yet unverified by practical testing. Certain is that bricks with paper are much easier to handle right out of the press.


documentation

The documentation process has gone splendidly. I have personally gained two fold by both learning wiki code and process, and also by forming my experience into consolidated bits of information. That this is now part of the public information set is truly grand.

Cost

      Sand
      Cement
      Boric Acid(ant poison)
      Trashcan
      Plywood
      Rakes(2)
      Shovels
      Storage Structure


Preparation

Earth calibration: After testing your soil, preferably in multiple locations, you will have an earth mix that is about 75% sand and at least 10% clay and less than 35% clay, by volume.(App. Bldg. Mat. p.223) The amount of cement needed will be relational to how close you are to this ideal, ranging from 3-5% to 10%.( App. Bldg. Mat. p.33, Bldg. Mat. Dev. Co. p.53). Now to think about making some compressed earth bricks...

Preface:

This is ideally a group activity. A minimum of two people are needed to operate a CINVA-ram. Four people is nice, six people is ideal in my experience. I will briefly describe a non-mechanical brick forming method that doesn't require any more than personal conviction, and minimal tools.

Materials needed(for non-mechanized mixing):

metal rake several buckets(1-3) mixing surface(sheet of plywood, where available, to avoid mixing with cement on ground) marker shovel measurer (ruler, tape measure, stick, etc.)

You will need to determine your mix as it relates to your buckets. If you are mixing down your earth with clay or sand you should be able to use the same method I've used to determine approximate cement quantities.

First, fill a bucket full of earth mixture, deposit this bucket on mixing surface. Fill the bucket again, but only to half full, use marker to mark half way point with line all the way around, label line. For that mater, label everything. This is a group activity and as such labels will help to avoid confusion and error. Deposit the second bucket on the mixing surface, form one pile, divide this pile into 10 equal piles. This may take a little work, don't try for perfection, do a decent job of it and proceed. Carefully place one of the piles into the bucket, make tiny tick marks around the bucket at height of the soil. Repeat this process twice more. Approximate these ticks measure. Now draw a line, up this measured distance from your half way line. Label this new line, which should be some small distance above your half way line, 'cement'. This gives you approximately ten percent cement stabilization when measuring. If you are testing to determine best mix ratio, vary your cement input from 10% to 5% by halving the distance between the 'earth' and the cement lines. Then again halved between the 5% test line and the 10% line. Some documentation points to the possibility of getting the cement percentages as low as two percent. However, if you are using another stabilizer you will likely have to use twice as much.

Now to actually go about making some compressed earth bricks...

Project

I attempted to employ the old "workshop = group labor camp" ploy, with limited success. The most successful work group ended up being my engineering 305 class. In general I have to say that I have grown to believe that most Americans are not particularly good at physical labor anymore. The literature proposes that the CINV-ram we have used, which by the way was made in Bogotá, Colombia, can produce between 40 and 60 blocks per hour( App. Bldg. Mat. p.33, Bldg. Mat. Dev. Co. p.342). The best performance we could squeeze from it was about a quarter of that, with a 14 person team.


Task Number of People
Digging 4 3 2 2 1 1 1
Transporting 3 2 2
Measuring and Testing 1 2 2 2 1
Mixing 2
Filling and leveling 1 1 1
Pressing 1 1 2 1 1
Raising out 1 1
Removing and placing to dry 2 1
Total Human Power 15 10 8 6 3 2



Teamwork means that there should be a smooth flow (See Table) of: Digging – Harvesting the earth from the best site, doing a rough sort, picking out big rocks and plant mater. Moving – Transporting the earth from the harvesting site to the mesuring/sorting/mixing site. Batching – Filling the buckets to the appropriate lines. Mixing – Evenly distributing the cement, or other stabilizer, with the rest of the earth. Testing – Drop testing the mix to ensure proper moisture level, adding water as necessary. Filling – Filling the void in the press, keeping the press area tidy. Compressing – Operating the press levers to compact brick. Releasing – Operating the press levers to release the brick. Removing and Transporting – Pulling the brick from the press operation and moving it to the storage area. Stacking – Stacking the bricks and setting aside any broken bricks for reprocessing. Smooth flow requires adaptation. Jobs overlap, bottlenecks naturally occur, people get tired, communication and fluidity of everyone's role are the tools that craft and efficient teamwork system.

Press operation is as follows

Experimentation

The compressed paper stabilized bricks that I formed are still curing, I will keep them wet(so the cement can cure) and test them in a month. That said, paper made the bricks much more durable out of the press. Processing the paper for mixing was exhaustive. I used a plastic trash can to store the paper in water.

I added an eighth cup of boric acid to the mixture of 50 gallons of paper and water to prevent molding. Molding is widely pointed to as a problem with papercrete (the product closest to what I'm experimenting with)((http://www.greenhomebuilding.com/articles/papercrete.htm). Yet, boric acid can be used as a, human safe, anti mold agent.(http://www.moldacrossamerica.org/borates.htm). My paper/water/boric acid mix was easy to handle and mold free for six weeks so far.

I blended the paper in the water after a week with a drill mounted mixing blade. Then again after another week. I then laid it to dry on a screen atop a pallet. After dry I crumbled it into a bucket and used the drill mixer again to reduce the particle size. I would rate this process as margionally successful. Far too much time invested, and the end product did not have small enough particle size for even distribution.

Discussion

This is a cursory look at compressed earth brick technology. The technology has become dominated by industry and all of my references are a decade or more old.

While the process is resource conservative, it is labor and time intensive.

References

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