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Re: GSBN:Leather Bales

On Aug 1, 2006, at 3:43 AM, brian wrote:

Hi to all,

I am unsure of the outcome of leather in bales, but it did prompt a question on my part. I have been contacted by an Aboriginal elder wanting to build homes for his people in Broome Australia. The humidity is high. Too high for
Straw bale. I would be interested to hear if anyone has baled plastic
bottles for building, as there is an abundance available. I would think that a cement lime render would be best if it was feesable. Does anyone have any

Brian, a Colorado (USA) architect, Doug Eichelberger, has built some experimental structures with plastic bales, and local University students did some associated testing.

I wrote that up in some detail for the upcoming book, "Design of Straw Bale Buildings"; here it is:

2.2.2  Plastic and other baled materials

Jean Nielsen built an experimental load-bearing structure of paper bales at the University of Arizona some years ago, and others have experimented with baled paper, cardboard, and pine needles, but there have been no reports as yet of promising developments.

Architect/builder Doug Eichelberger is experimenting with baled plastic water bottles, and collaborating students at the University of Colorado conducted a cursory battery of tests from which the following comments are drawn.

Figure 2.2A

Plastic Bales	

photographs courtesy
Doug Eichelberger
and George Nez


Advances in technology or changes in economic conditions can affect a building materialÕs viability, availability, and usage. As an example, plastic is a petroleum product; thus its price follows the price of oil. Today [2005] in the United States discarded water bottles have a recycled value of as much as $0.30 per pound, partly due to material value and partly due to labor and transportation costs. These costs have risen exponentially in the past ten years, and in some cases this kind of plastic used for a foundation may cost as much as concrete. However, agencies such as The World Health Organization have noted the growing problem of plastic waste in developing countries. This problem is hugely exacerbated after a war or natural catastrophe ravages an area, triggering an influx of food, water, and other aid in plastic bottles and packaging. Could baled waste plastic be a shelter solution for developing countries? Plastic as a raw material has an extremely long life, is moisture- and decay-resistant, and is lightweight and strong. The building technology is both simple and ancient: stacking blocks or bales of materials on top of each other to create walls.

Building a test structure is the best means of trying out a new material, both for its inherent properties and as a system. In the 1990Õs Doug Eichelberger built the first permitted prototype, a 36 x 48 foot [11 x 14.6 meters] barn, followed by two bale homes in the mountains of Colorado. All of the structures were constructed with plastic bale foundations and difficult-to-recycle paper bale walls.

His current project, described here, uses bales of household plastic to create both foundation and wall systems. The project starts with collecting the plastic bottles and baling them into building blocks. Previous projects had used large, heavy bales (1800 lbs. [816 kg.] each), requiring machines to move and stack. This new process involves much smaller bales that can be moved and stacked by hand, much like straw bales.

In EichelbergerÕs current project, the large bales were broken down and rebaled on site. The baler is small by industry standards (used balers like this are available all over North America for between 500 and 2000 USD), was loaded manually, and the three-wire tie-off was also done by hand. The resulting bales weighed about 40-45 lbs. [18 to 20 kg.], their dimensions were approximately 30 x 24 x 16 inches [76 x 61 x 41 cm], and they took about 15 minutes to make.

Despite the simplicity of the machine and process there were numerous variables. The baler ram force is a constant, but the actual material amount varied, so, like straw bales, the bales could expand in length from 24 to as much as 30 inches. The wires were hand-tied when the ram had the material in maximum compression; when the ram was released, the bales then expanded to the wire tension. That tension varied from person to person, and according to the time of day and an individualÕs fatigue level. Eventually the project team devised a crude tool that maximized tension at a somewhat consistent rate. Even with this improved process, however, a range of bale strengths, weights, and sizes were produced but manageable.

Stacking/ stabilization
Since plastic bales are unaffected by moisture they were used for the foundation, though the long-term durability of the wire ties is unknown. The bales were simply placed in a rough trench and pushed as close together as possible. The site slopes slightly, so the foundation varied from one to two bales deep. Colored plastic bales were used for the foundation, as they were rougher in shape. Above grade, two different wall types were constructed: load-bearing (bales flat, 16 inches high) and infill or post-and-beam (bales vertical, 24 inches high).

Due to the strength of the plastic and the confused orientation of the material in the bales, it was impossible to drive spikes through the assembly to gain stability. Also, the slick, slightly convex surface of the bales and the stiffness and memory of the bottles made tight stacking difficult.

Bale proportion also became a stacking complication. A typical straw bale or adobe brick has a 2:1 dimensional ratio, making a running bond easy to accommodate. The running bond creates a sort of lock to the bale courses. The baler used created a more square bale which made a running bond and its locking qualities impossible.

The solution for all this was a panelization process using vertical stabilizers and a simple form of post-tensioning. Since internal spikes proved so difficult to install, #3 external vertical reinforcing bars were sunk into the ground on the outside of the bales and tied together at each bale course, creating a series of quasi-columns. Next, poles were placed vertically at the end of each run of bales. Wires were run horizontally and tied tight, pulling the panels of bales together to create a unified wall. The next form of post-tensioning used a wood plate laid on top of the wall with wires tied over the plate from side to side and fastened at the bottom (as is often done with straw bale walls). Through this process the walls were compressed vertically as much as 4 inches. This system also allowed the top plate to be leveled. These stabilization methods were used in both wall types, and appeared to greatly strengthen the walls prior to roof loading.

A simple roof structure was installed and finished to load the walls prior to finishing. The above-mentioned top plate became the bearing point for 2x wood rafters on the load-bearing wall. External wood columns and a wood beam carry the load on the opposing wall. Corrugated metal is the roofing material. The structure was left open so that added load could be applied to test differential loading and settlement.

One-inch stucco netting was fastened directly to the bale wires and tie-down wires using cage clips and hog rings. Gaps between bales were filled with loose plastic bottles to reduce stucco thickness. A cement stucco base coat was mixed using 1/3-inch pea gravel as filler for the first/ filler coat. A typical one-coat topping was applied as a finish.

Lab testing
Testing on plastic bales was completed in the spring of 2005 at the University of Colorado1; results can be viewed and/or downloaded at <a target="_blank" href="http://www.edc-cu.org/ppt/PlasticBales.pdf";>http://www.edc-cu.org/ppt/PlasticBales.pdf</a>. The bales showed a range of strengths as follows: &#xA5; Compressive strength up to 5 psi [35 kN/m2] at strains between 0.15 and 0.28
&#xA5;  Modulus of elasticity of 30 psi  [207 kN/m2] +/-
&#xA5;  Density of 4 to 10 pcf  [64 to 160 kg/m3]

Since the wall system required a panelization/post tension approach, further lab tests will be completed on bales configured in those conditions. From those results structural design criteria can be established. Further tests could evaluate a plastered bale wall&#xD5;s insulative qualities.

In urban areas of the industrialized world, large amounts of plastic are typically available from local recycle centers. Depending on local collection processes, recycled plastic comes in three basic categories: PET (Polyethylene Terephthalate; water and soda bottles, which have the most value), HDPE (High Density Polyethylene milk jugs of lesser value), and finally colored plastics which include detergent, juice, and some food product containers. They typically are available in large bales, allowing transport of a greater amount of material in a small volume. (PVC, or Polyvinylchloride, is at once among the most useful, ubiquitous, toxic, and nearly impossible-to-recycle plastics in the marketplace.)

Potential problems
Baled, recycled plastic poses several problems that limit their utility as construction materials: &#xA5; Variability in bottle sizes and strengths&#xD0; Sizes ranging from two liter soda bottles to tiny prescription drug bottles make for highly heterogeneous bales; &#xA5; Lids&#xD0; Some bottles still have their lids while others don&#xD5;t; bottles with lids are harder to compress, and the lids make the bottles want to return to their original shape; &#xA5; Some bottles still contain some of their contents, making for potential insect or mold problems; &#xA5; Once plastic catches fire it is difficult to extinguish, and fumes emitted from plastics can be toxic. Furthermore, some bottles contain volatile materials like oil or lighter fluid; &#xA5; The reliance on metal wire ties, particularly below grade, requires long-term protection from corrosion.

The test structure appears to be a success, as it is carrying load without distress. The passage of a few years will reveal any freeze/thaw problems, differential movement, or other problems should they occur.

What is the appropriate use of waste plastic? The high cost of plastic in the industrialized world may make baled plastic construction unpractical there. On the other hand, areas of war, poverty, tropical climate, or natural disaster that already have a surplus plastic problem are also places where the availability of material and labor, coupled with the need for simple shelter, creates an opportunity&#xD1;or even need&#xD1;for baled plastic construction.

Figure 2.2B

Plastic Bale

photographs courtesy
Doug Eichelberger
and George Nez

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