| Building and Living In Paper - 2018 |
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Paper is principally wood cellulose, which is considered a fibrous material. Cellulose is the second most abundant material on earth after rock. It is the main component of plant cell walls, and the basic building block for many textiles and for paper. Cellulose is a natural polymer, a long chain of linked sugar molecules made by the linking of smaller molecules. |
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| Cellulose hydrogen bonds. |
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| The links in the cellulose chain are a type of sugar: ß-D-glucose. The cellulose chain bristles with polar -OH groups. These groups form many hydrogen bonds with OH groups on adjacent chains, bundling the chains together. The chains also pack regularly in places to form hard, stable crystalline regions that give the bundled chains even more stability and strength. This hydrogen bonding forms the basis of papercrete's strength. |
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 | Viewed under a microscope, it's possible to see a network of cellulose fibers and smaller offshoots from the fibers called fibrils. |
| Fibrils are offshoots of fibers. | |
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 | When these networks or matrices of fibers and fibrils dry, they intertwine and cling together with the power of the hydrogen bond. |
| Fibers and fibrils network to form a matrix, which becomes coated with Portland cement. | |
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Coating these fibers with Portland cement creates a cement matrix, which encases the fibers for extra strength. Of course paper has more in it than cellulose. Raw cellulose has a comparatively rough texture. Kaolinite or China clay is used to add smoothness and semi-gloss to paper. Varnish is added for the glossy look. Then there are various inks and other chemicals added. Many types of paper are treated with dyes and bleach that can contaminate soil and plant-life. They are extremely persistent in soil and cannot be broken down by bacteria. It makes sense to encase them in Portland cement, keep them out of the landfill, and do something useful with them.
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| Samples made in a coffee can showing shrinkage. From left to right: No Portland cement, 50-50 cement to paper, 60-40 cement to paper. |
Portland cement is an integral component of papercrete. It is usually not used in fidobe or padobe. A simple paper and water mix takes a great deal of time to dry and it shrinks about 15-25 percent. Adding Portland cement in an amount equal in weight to the paper cuts drying time by about half and reduces shrinkage to about 3-5 percent. If nothing were added to paper and water, it would be less strong, highly flammable, and less resistant to bugs and mold.
No matter what mix you settle on, the great thing about generic papercrete is how it traps air. When the water drains out and evaporates, it leaves thousands of tiny air pockets. This is what makes the material light and a good insulator. Adding solid material to the mix (sand, etc.) affects weight and insulating quality. The best mix is the one which best fits the application. |
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| Because there is so much waste paper in the United States, it is probably the best fibrous material to use here. But there are many other natural fibrous materials, such as f lax, hemp and jute, which could be used to make papercrete in other parts of the world . Less obvious candidates include: straw, wood fiber, kenaf, wheat, barley and cane. Natural fibers have the advantage of being renewable. Also, many natural fibers, including pineapple leaf fiber and water hyacinth, are waste products and are available at minimal or no cost. Research is now being done to incorporate composites of these materials in ways previously unimagined. Ford Motors, for example, is committed to using wood and natural fiber-reinforced composites for structural purposes. Doing this would take these materials well beyond their present cosmetic uses in trim. Ford has even predicted that car bodies themselves will be constructed from natural fiber composites in the medium term.This brings us back to some of the derivatives of papercrete - fibrous concrete, padobe and fidobe. Fibrous concrete (a.k.a. fibrous cement) is fibrous material (usually paper), Portland cement and water. Padobe (paper adobe) has no Portland cement. It is a mix of paper, water, and earth with clay. Fidobe (fibrous adobe) is like padobe, but may contain other fibrous materials. Actually, classic adobe was made with clay earth and straw - so is adobe actually fidobe? I would guess so. There are no hard and fast rules, but recommendations are on the horizon. |
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Papercrete is mixed with Portland cement to obtain a very good R-value (2-3 per inch), an excellent sound absorption quality, to be flame/fungus retardant, and bug/rodent resistant. Since it is relatively light and more flexible than earth, rock or concrete, it is potentially an ideal material for earthquake-prone areas. It can be used in many ways -- as blocks, panels, poured in place, augured, pumped, sprayed, hurled, troweled on, used like igloo blocks to make a self-standing dome or applied over a framework to make a roof or dome. Papercrete is a very forgiving material, but like any other mixture, varying the mix, admixtures and curing procedures results in tradeoffs in its properties. For example, adding more sand or glass to the mix results in a denser, stronger, more flame retardant material, but adds weight and reduces R-value. Heavy mixes with added sand, glass, etc. increase mass and strength to a point, but reduce workability. In other words, a "light" mix with just Portland cement is easier to cut with a chain saw and drive rebar through than a mix with larger amounts of sand, clay, etc. Adding more than the minimum amount of Portland cement to the mix increases strength and resistance to abrasion, but also reduces flexibility somewhat, adds weight and may reduce R-value. So the trick is finding the best mix for the application. Making walls calls for a lighter mix than stucco. Roof panels will probably be a different mix than sub-floors. |
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| A tow mixer being pulled behind a pickup truck. |
The most common mixer in use is Mike McCain's tow mixer. See Mixers. It has a capacity of about 200 gallons (900 liters). The following is a starting formula for a 200-gallon batch of blocks. A 200-gallon batch will make 25-30 blocks in forms one foot (30 centimeters) wide x two feet (61 centimeters) long x five inches (13 centimeters) thick.. See Forms.
A starting formula is just that, a place to begin experimenting. Some people prefer "lighter" formulas without sand. If you plan to cut out windows, doors or other openings in the walls after they are erected, you will want to avoid using sand. It will dull your chainsaw blades very quickly.
But a typical starting formula for a 200-gallon batch is 160 gallons (727 liters) of water, 60 pounds (27 kilograms) of paper, 1 bag or 94 pounds (43 kilograms) of Portland cement and 15 shovelfuls or 65 pounds (29 kilograms) of sand. The sand adds thermal mass, reduces flammability and shrinkage, and packs down the slurry for a denser, stronger block. See above for caveats regarding sand.
Half a bag of Portland cement will work too, but the slurry will dry more slowly and will shrink more. The blocks won't be as hard or flame retardant when dry. Some people use two bags of Portland cement in areas where strength is most important - for blocks at the bottom of walls, roof panels, and for floors.
Clyde T. Curry's recent formula for one yard (about 200 gallons) of papercrete incorporates 25% reground Styrofoam. His formula calls for three sacks of Portland cement added to 75 pounds of hammer-milled cellulose insulation and 25% reground Styrofoam. This cuts the amount of Portland cement he normally uses by one full sack and significantly reduces shrinkage. He makes his interior plasters using six sacks of Portland cement per yard, which makes the plaster fire resistant and forms a flame/vapor barrier equivalent to half-inch drywall. |
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If you are opposed to using Portland cement, you should try some experiments with paper and clay and with other binders (see Other Binders below). There are some interesting websites on the internet, which give some fascinating insights into "paperclay." What you need for fidobe (any fibrous material and earth with clay) or padobe (paper and earth with clay) is a fibrous material or paper, and earth with high clay content. The clay content of the earth should be at least 30 percent. With regular adobe, if the clay content is too high the adobe may crack when drying, but adding paper fiber to the adobe mix strengthens the drying block and gives it some flexibility, which helps prevent cracking. The earth (with clay) to paper ratio can be varied for different applications. Since earth is different in every location, do some baseline experiments with 4-to-1 ratio - earth to paper, by weight. This is a good place to start in order to find a mix for a strong, lightweight block.
If Portland cement in small amounts is acceptable to you, you might try ratios like 6:3:1 or 7:2:1 paper, earth, cement. Basically, the more clay in the earth, the more paper you can use, but the binder should not fall under ten percent.
In the above ratios, keep in mind that the paper should be pulped with water before the other ingredients are added.
Before mixing the above ingredients, screen the rocks and small stones out of the earth. Again, the earth should have 30 percent clay or better. If you are wondering how you determine the amount of clay in earth, there are two easy ways. First of all, make sure you are testing earth with no organic materials in it. Usually that is found below the roots of plants and grass a foot or two underground. If you want to test a large volume of earth for clay content, make sure you a get a few handfuls from different points in the sample area and mix them together before screening. If there is any clay present, and it is the slightest bit moist, (spray some water on it if necessary) it will stick and cake up on your shovel making the shovel quite heavy. Take a handful of this damp earth and squeeze it. If it stays intact in a lump, it has some clay in it. If it can be rolled out into a "worm" without breaking up, it has more clay in it. If the worm can be draped over the edge of your hand about three inches and stay intact, it has quite a bit of clay in it. |
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| If the earth stays in a lump after squeezing, it has clay. | If a worm can be made, it has more clay. | If the worm will hang, it has a lot of clay. |
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To determine a fairly exact percentage of clay, do a simple "shake test". Using a vertical-sided transparent jar or glass which will take about a quart of liquid, fill it about two thirds full of water and almost the rest of the way with earth. (Leave a little space for shaking.) Then shake vigorously for at least two minutes. Set it down and start watching the separation. Earth should have some percentage of sand, silt and clay in it. Each material is basically a little more coarse and heavier than the other. Sand and heavier particles with fall to the bottom almost immediately - within a few seconds to a minute. Silt will settle on top of the sand in a few minutes to several hours. Clay will settle on top of the silt within several hours to 24 hours. Best to wait 24 hours for an accurate reading. There will be a faint but discernable delineation between each layer of material present. Of course, if any of the three materials - sand, silt, or clay is not present, there will be no layer. The percentage of clay can be determined by measuring the layers, and figuring the percentages, based on 100% of the total height measured. If the clay is about thirty percent of the height of the earth, you can make blocks. If it's within a few percent, you may want to use a little Portland cement to make up the difference.I have seen something which makes me believe that going totally without Portland cement could be a problem - termites on the surface of a papercrete block. I was visiting a building site in New Mexico. Several hundred double fist-sized pieces of papercrete had been tossed in a pile and over a period of weeks had settled into the damp worksite soil. I began turning over pieces looking for any kind of damage. For some time I found nothing at all. Pieces embedded in damp mud for a long time were perfectly clean and intact. Then I found one, which had a small piece of unmixed paper embedded in it, which had been in contact with the damp soil for some time. The paper was not coated with Portland cement. There were a number of termites around the unprotected paper. The paper and mud scraped off very easily and I carefully examined the rest of the surface of the piece. It was completely clean. I then tried to break the piece into smaller pieces to look inside. It wouldn't break up and the small pieces that did come off left completely clean surfaces - no dirt tunnels or other evidence of termites. I believe that the uncoated piece of paper was the only thing drawing the termites. I have heard that some people put a shovelful of Borax in their mixes to discourage bugs. I have examined other buildings, five to nine years old, which I'm sure were built without Borax and they showed no obvious signs of bug attack.
Please consider a safety note on formulas. Unless you add a significant percentage of non-flammable material to any mix, both papercrete and fidobe (or padobe ) will burn. Papercrete made with a 4-to-1 ratio of cement to paper, by weight, won't burn at all, but that may be too much cement. Papercrete made with a 1-to-1 ratio of cement to paper, by weight, will smolder like charcoal, but does not burn with an open flame. Smoldering with no flame could result in unlikely but dangerous scenarios.
One practitioner is particularly sensitive to the possibility of a roof collapse should wide areas of a papercrete wall smolder for hours without detection. Another practitioner tested this possibility and thinks that such an occurrence is highly unlikely. He bored a three-inch hole in a papercrete wall and emptied an entire can of lighter fluid inside. He managed to get the papercrete to begin to smolder, but it would not continue to smolder for long because of lack of oxygen. It was suggested that fireproof mortar (high percentage of Portland cement or other fireproof binder) be used between the blocks, and fireproof stucco be used on the outside of the home to "encase" the blocks in fireproof "containers". This would limit a smoldering fire to the destruction of only one block, if it should ever occur at all.
Fidobe or padobe made with 3 parts soil to one part paper, by weight, supposedly won't burn either. Again, that may be too much soil. The intention is to be safe, but not sacrifice the qualities (R-value, light weight, strength, etc.), which make papercrete and its variations attractive to use in the first place.
More testing needs to be done on papercrete and fire. |
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There are alternatives to Portland cement, which can be used as binders, either alone or in combination with Portland cement. They include fly ash, bottom ash, rice hull ash, Plaster of Paris and lime. There may be others. Fly ash is ash left over from burning coal, which in the past was allowed to fly out of the smokestacks of power plants into the atmosphere. It is now caught in giant air filters, bagged and sold. I examined several structures built with papercrete block using fly ash and Portland cement in a 35 percent to 65 percent ratio as a binder. They were five years old and in excellent condition. Using fly ash as 35 percent of the binder cuts the Portland cement cost nearly in half and helps recycle fly ash. Bottom ash is heavier than fly ash so it sinks to the bottom of the furnace. I have heard of bottom ash being used, but have not seen papercrete made with it. Rice hull ash is burned in power plants in areas of the country where rice is grown. We currently have 100 pounds (45 kilograms) of rice hull ash on standby for tests. Test results with rice hull ash will be posted in Tests soon. Plaster of Paris is a variety of calcined gypsum. You probably have seen it in the form of drywall sheets. In powder form, it is really quite expensive, but in situations where it is necessary to join papercrete and wood, it is very effective. A small sample made with it was placed on a 2 x 6 piece of wood and was very difficult to pry off with a trowel. The papercrete seemed literally glued to the wood.
Hundreds, if not thousands of years before Portland cement was discovered, lime was used as a binder, mortar and plaster. The Romans used it in their stone construction. It can be purchased in most home improvement stores.
More tests need to be done on all of these binders. We will be working on testing them later this year. |
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It took me some time to get over my skepticism about papercrete. I mixed up small batches and tried different formulas. Since I have no allergies, and was used to thinking in terms of bricks and mortar, I just felt more confident using Portland cement. I found some recycled plastic five-gallon buckets to work in and bought an "X" shaped stucco-mixing blade for my heavy-duty drill to do the mixing.
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| X-shaped stucco mixing blade. |
The drill won't win any RPM contests, but has great low-end power. I would advise staying away from the normal kitchen blender for doing experimentation. I burned out a blender and a circular saw (I had custom adapted it for mixing.) before I realized that those tools are really meant for high speed and relatively low torque. Recently, I was told that a heavy-duty food processor works well to mix papercrete samples. What you need to mix papercrete is power. You need to tear the paper apart and mix it, which requires a good deal of force. This is the reason that Mike McCain's tow mixers work well - they provide the power of an automobile engine to tear apart everything from office paper to phone directories.
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| 1250 pounds on block made of paper and water only. |
After carefully weighing the components with a three-bar scale and mixing small batches, I poured samples in open-ended coffee cans and placed them on shade cloth to drain. I usually waited about an hour to remove the coffee can. The samples dried in about four days in the hot and dry weather of the Phoenix area . I recommend that anyone considering papercrete do a little experimentation to build confidence in the material. My confidence soared when I let down a front tire of my truck - over 1200 pounds (545 kilograms) on a bread-loaf size piece of papercrete made with just paper and water. It didn't leave a mark on the papercrete. Supposedly, computerized algorithms could tell me what would happen if I left the truck there for 200 years.
now adding some type of adhesive to the mix of paper and then adding your cement and Earth don't forget your additive this terms ordinary earth inot clay. |
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Anecdotally, a lot is known about papercrete, but not much has been formally tested. We will be testing as many parameters as time and funding permits. As results become available, they will be posted at the end of this section. In order to gain visibility and acceptance in the marketplace, a battery of tests will have to be run, standards set and quality controls initiated. Some of the tests which need to be run, after a standard mix is established, are as follows:
Material Characterization - Compressive strength, tensile strength, shear strength, long term deformation (creep), water permeability, fire resistance, heat and sound insulation, long term behavior (degradation).
Structural Elements - Strength in pure bending, strength in axial force and bending moment, strength in shear, effect of reinforcement.
Although we may not be able to accomplish all of this testing in the near future, these are the types of tests which will be required over time to provide architects and design engineers the information they need to establish papercrete as a mainstream building material.
 | We have tested more than 50 different combinations of materials. We are looking at various percentages of Portland cement, Portland and sand, Portland and fly ash, Portland and rice hull ash, clay, Styrofoam, lime and paper mill sludge. We first look at compressive strength. Then we examine thermal properties, creep and pull tests. We have also investigated cure time by testing identical samples over time. Blocks made adobe style vary from blocks made in a press. Pressed blocks are much stronger, more regular and water efficient. |
| Test samples drying on shade cloth. | New TECHNICAL REPORT now available. |
The basic constituents of the test mixes are:
1. Paper/Portland Cement
2. Paper/Portland/Sand
3. Paper/Portland/Fly Ash
4. Paper/Portland/Rice Hull Ash
5. Paper/Portland/Styrofoam
6. Paper Mill Sludge/Portland./Fly Ash
7. Paper/Portland/Glass
8. Paper/Portland/Clay
9. Paper/Portland/Lime
*10. Hammermilled paperAfter initial tests on these mixes, we will narrow down the alternatives and try cross-over mixes based on which initial mixes test best. For example if, the Paper/Portland/Styrofoam combination has a superior compressive strength, we may want to try Fly Ash as a substitute for a percentage of the Portland cement to see if we can reduce the costs of the mix. Other tests involving ground low-grade paper and cardboard are also planned.
We recently sent a sizable sample of junk mail, paper packaging, and other paper collected around the house to Schutte Hammermill in Buffalo, New York. They are helping us research the proper hammermill and screen size to use for "hammering" low-grade mixed paper into a dry fibrous mass, which can be more easily handled and mixed than un-milled paper. Using "hammered" paper would allow mixing in a conventional rolling mixer or even a cement truck with a rolling mixer.
Specifications for papercrete do not yet appear in ASTM and extensive engineering tests have not yet been run on papercrete. We have begun contacting officials in the ASTM organziation and the ICC to determine a procedure for seeking approval of one or more of the mixes we are testing. More testing needs to be done in recognized and controlled engineering environments. That having been said, there are a growing number of homes and other structures built of papercrete (some of which have been standing for many years) so there is little doubt that papercrete works well as a construction material.
The compressive strength of papercrete has been measured a number of times and is variously reported to be in the 140-160 lb./sq. inch range -- but compressive strength is probably not the most accurate way to judge papercrete. Compressive strength is a measure of load at the instant of failure. This works for concrete because when concrete's load is exceeded, it literally explodes. When that point is reached, the compressive strength is known. But papercrete never fails catastrophically, it just compresses like squeezing rubber. So a more accurate measure of papercrete's strength is its stiffness - in other words, how much does it compress under what load? We have found that this value is less than the compressive strength of concrete, but many times greater than would be needed to support any kind of roof combined with just about any roof load. So with papercrete, you don't have the sudden catastrophic fragmentation, which is characteristic of concrete or earth, just a slower squish. When the load is removed, papercrete actually rebounds a bit in an attempt to return to its prior shape. What does this all really mean? It means that papercrete has no problem with strength. A structure several stories high can be built with it. The next issue is creep. What will happen to a papercrete wall under constant load over time? Will it slowly compress or will it keep its shape?
The tensile strength of papercrete also seems sufficient to the task. Just try to pull a single sheet of paper apart by pulling laterally on the edges. It has great strength. Ripping a piece of paper is much easier than pulling it apart. So the shear strength of paper is not as great as its tensile strength. But a papercrete block is the equivalent of hundred of pages of paper - almost like a catalog. Papercrete has very good sheer strength as a block. Lateral load involves sideways force - the wind load on the entire area of an outside wall for example. Because papercrete walls are usually a minimum of twelve inches thick, and usually pinned with rebar, they are very strong laterally. No extremely long lengths of flat wall built with any kind of material should lack reinforcement. The reinforcement might be internal - using mesh or rebar, or external by curving the wall or connecting the wall to perpendicular walls at reasonable intervals. Structural testing will tell us the best way to design for papercrete construction. Again, papercrete is not yet part of the Universal Building Code, but in practice works very well.
"R-value" is a measure of a material's resistance to heat flow. The R-value of papercrete is reported to be between 2.0 and 3.0 per inch - the higher the number, the better. I have seen documentation from the Department of Energy, which was done on two samples of Lex Terry's blocks. Lex uses a 1:1 mix of Portland cement with Fly ash to paper, with about 12 shallow shovelfuls of sand added. His two samples came back from DOE with R-values of 2.24 and 2.16. The percentage of Portland cement and fly ash was 65% Portland cement and 35% fly ash. Lex makes his blocks 12 inches (30 centimeters) thick. He adds an average of about an inch (2.5 centimeters) of papercrete exterior stucco and about the same amount for interior finish. That means that his total R-value will be at between 30.24 (14 x 2.16) and 31.36 (14 x 2.24). That's quite good compared to an older standard wood frame wall of R- value 19. The R-value of hollow masonry block is only 1.75.
Fire -
There have been several reported incidents involving papercrete and fire. One of them was a case of arson. A gallon can of gasoline without its top was thrown on the roof of a papercrete shed – followed by a lighter. The accelerant eventually caused the papercrete to begin smoldering like charcoal. A volunteer fire group responded and had to return several times before they understood that papercrete smolders and does not burn with an open flame - they thought the fire was out. When they thoroughly doused the smoldering area with water and scraped out the blackened material, they put it out. Firemen in larger cities routinely do this when putting out fires in blown-in attic insulation, which is similar to the pulped paper in papercrete.
Another fire was caused by a plumber, while sweating on copper water-line connectors with a torch. Apparently he didn’t use something to shield the paper blocks from the torch. No one noticed that a block had started to smolder. When someone did notice, 36 hours had passed. The blocks in a four-foot square section of wall had been reduced to ashes.
While the issue of fire should never be minimized, I think a wider perspective is helpful. In my area of the country, several construction fires caused by grinders, torches or welders make the evening television news each year. There are numerous other fires, which are contained by workers themselves and don’t get broadcast. In some cases, these fires result in spectacular losses, which occur in less than 20 minutes – and once in a while people get hurt or killed. When these things happen there is never a suggestion that wood should be outlawed for construction purposes.
My point is this. I would rather live in a structure, which would give me hours and hours to locate and fight the fire than in one, which would incinerate me before I can get to the front door.
Having said that, caution is always the best policy. Watch what you’re doing with anything that gets hot or produces sparks or flames around this material, or wood, or fabric or anything else that might burn. I once pounded a piece of rebar into a papercrete wall, which veered off vertical and came out through the wall right where I wanted to locate a door jam. I didn’t want to go through the trouble of extracting the rebar so I decided to cut it back from the door jam by slicing into the block with a grinder. I knew there was a fire risk so I had a bucket of water nearby. I sliced into the block with the grinder and cut off the rebar in a hail of sparks that lasted several minutes. I thought I would surely set the block on fire, but it didn’t burn. I stuck my pinky back in there when the rebar had cooled, and watched it closely for a few hours while working in the area, but no fire. Maybe it was because I use quite a lot of Portland, fly ash and sand in my blocks. The more inert ingredients in something, the more difficult it is to burn.
I think the question is does papercrete catch on fire more easily than other materials and I really don’t believe that it is more flammable than anything else under normal circumstances. Anything - even rock - can be burned when the conditions are right.
Our block and roof panel mixes cure into a material which will not burn with an open flame. If an accelerant like gasoline is applied to it or it's held over an open fire for a prolonged period ( 30 seconds or more) it will begin to burn slowly like charcoal rather than rapidly like wood.
| It will eventually be reduced to ashes, but a single block will take several hours to be consumed. However, I recently witnessed a way to treat it so that it will not burn at all. Artie Skeeter, from Blue Lake, California working with Shane Keller from Arcata, California, tried some textile fire retardant on papercrete. Many fire retardants are expensive and give off toxic fumes, but a mixture of boric acid and borax is environmentally friendly and will protect the block from fire. Boric acid is used in eye washes. This concoction has been used for years to treat curtains, draperies and other textiles in theaters, playhouses and dance clubs where people congregate in great numbers. |  |
The National Fire Prevention Association (Reg. 701) Standard Methods of Fire Tests for Flame Propagation of Textiles and Film (1977) provided some uncomplicated formulas. |
This paper Crete, coated with a boric solution, was held in an open flame for two minutes.
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Artie and Shane settled on 1 cup of Borax and 1 cup of Boric acid in a gallon of water. It's not too expensive and the great thing is that it seems to work. Another great thing is that it's not necessary to treat all blocks. The interior plaster and exterior stucco used with papercrete contains a high percentage of Portland cement. That in itself will not burn. So the only weak point is inside the block near electrical outlets, switches and other places where wires goes through walls, into boxes, etc. Properly wired, these places should never cause a fire, but many home fires are
 | traced back to faulty installation of wiring. So if you want to be extremely safe, we recommend soaking the outlet holes, switch box holes and anywhere wire goes through walls with the above solution before installing the boxes. This is not to say that papercrete will never burn. Any material will burn or melt if enough heat is applied - even rock. But for all practical purposes, papercrete is relatively safe (safe as or safer than wood) without being treated. It's even more safe with the boric acid solution above. |
After two minutes in the fire, it blackened but did not catch fire,
smolder or burn. | |
Wicking -
Much had been written about wicking - that is the capillary action of liquids (in this case water) through construction materials such as concrete. The idea is to prevent water from wicking from the ground through the footing and up the stem wall (defying gravity) into the papercrete wall - a potentially serious problem.
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| A simple wick test. |
Since we mentioned using sand bags for a foundation - seeFoundations , we wanted to double check that such bags wouldn't wick. We first filled a bag with what looked like sandy soil. We placed the bag into a metal basin and filled the basin with water half the depth of the bag. Within two hours, the top of the bag was sopping wet. The water had defied gravity and climbed to the top of the bag. We were amazed that this had happened since the soil we used was quite sandy, or so it appeared. We ran a "shake test" on the soil - see FORMULAS - Fidobe and Padobe - and found out that the soil was actually 30 percent clay. We then repeated the test above with "all purpose" sand purchased from Home Depot. We allowed the bag to sit in water over night and there was no wicking at all. It is not a secret that sand will not hold water, but we were somewhat confused by the fact that soil can appear so sandy and yet, in combination with clay, wick like a sponge. So, the lesson is if sand bags are used for the stem wall, make sure the sand is really sand. If the sand is not purchased - that is, obtained from a river bottom or other source - be sure to run a wick test as described above before using it. Since the test is so easy, it might be a good idea to test every load to make sure that other soil types are not contaminating the sand.
Glue -
 | These two pieces of papercrete were cut and ground for test purposes. Their finished dimension was 3 1/2 x 3 1/2 inches (about 9 x 9 centimeters). We wanted to find out how well conventional white glue would hold the pieces together so we put a medium amount of glue (several tablespoons) on the bottom piece, layed the top one in place and let them set over night.
The result was remarkable. They will not come apart. We have tried everything short of destroying the pieces to get them apart. |
This would seem to indicate that papercrete could be used in applications calling for quick assembly by cutting the pieces to size in advance and letting the user simply glue them together.
We will be posting the results of engineering structural tests and other informal test as they become available. |
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