Have been meaning to dig into my notes and share this with you for about a week but have been too busy with my project to stop and hunt this info up.
Here is some information I gathered from reliable, experienced sources regarding using asphalt emulsion in soil -- and in soil and paper fiber -- mixes. It mostly comes the experience of those making adobes -- which are more dense than papercrete.
Am also including some info, deeper in, on cactus juice and cow manure and some other stabilizers that help with adhesion and water resistance.
First a few notes on the amount of asphalt emulsion to use. You can experiment, using this info as a guide, to find your best mix:
1.
Bitumen
(kwcnote: Bitumen means asphalt.)
Bitumen is added in the form of an emulsion that is in suspension in water or another liquid medium. On drying the bitumen forms a thin film which coats the soil particles. The main effect of adding bitumen is to improve cohesion and water resistance. However, if it is added
in excess the compressive strength can be reduced.
Normally the quantity of bitumen to be added (excluding the solvent or water) is 2 to 3% for a cutback (solvent-based), or in the following proportions for an emulsion:
- 4 to 6% for a soil with a high sand content;
- 7 to 12% for low sand content soils;
- 13 to 20% for clayey soils.
The bitumen needs to be mixed with a small quantity of soil before mixing it with the remainder; the mixing needs not to be excessive to avoid breaking down the emulsion and making stabilization less effective.
-- http://sheltercentre.org/sites/default/files/PA_AdditivesClayMineralsSynthetic.pdf
2.
This is the mix Quentin Wilson uses in Adobe brick making:
"Adobe with about 4% asphalt is quite waterproof. In the USA the asphalt is quite emulsified through chemical magic and mixes easily with water. ...Do not put on an exterior sealant. Many types of sealants have been tried and if they do not breathe, any moisture that gets into the adobe cannot get out and breaks the bond of the sealant at the surface of the adobe. Asphalt will do the job."
-- http://www.greenhomebuilding.com/QandA/adobe/mixes.htm
"..."I would stick with the asphalt emulsion stabilizer. The amount I favor is about 12 to 16 ounces per wheelbarrow. That's about a 3- to 4-cubic foot load in the wheelbarrow. Actually, I mix in a mixer but after several loads counting shovelsfull, I can judge how much is in the mixer before I pour it into the wheelbarrow. At that low rate of asphalt, the mixture is still moisture vapor permeable. It has held up well on the exterior of the church here in El Rito with some touch up over the past 20 years.
"I have used Elmer's Glue but only on interior walls and then only when the soil was very sandy. Most good adobe mixes work on the interior without metal netting or any admixture. I would not use both stabilizers in the same mix. I get emulsified asphalt from Elf Asphalt which I think is nationwide. They supply to the highway and driveway repair industries. They may have quirky requirements in the amounts they will sell and into what kind of containers they will deal with. There might be other asphalt suppliers in your area."
-- ibid
-- "I find that 8 to 16 liquid ounces is about right to stabilize a cubic foot of my soil's adobe mud. That is about 1/2 to 1% by weight. It is not fully stabilized but will give enough protection to preserve the adobe for my lifetime. Another way to add is to put 5 gallons of emulsion into a 55-gallon drum and fill it the rest of the way with water. That way the water has 10% asphalt. It is a little nicer to work with than full strength emulsion."
-- http://www.greenhomebuilding.com/QandA/adobe/mixes.htm
3.
On the use of various stabilizers for strength and water resistance:
Q: Can you give me an idea of the percentage of material to adobe I should begin with?
A: Emulsified Asphalt: 1 to 5%; Cement: 3 to 7%; Lime: 2 to 9%; Fish oil emulsion: 1 to 3%; Carpenters glue: 1/2 to 2%; Resina or latex/acrylic: 1/2 to 4%. Every soil is different in its clay/silt/sand ratios so it just takes fooling around. I can usually tell when the mud just begins to feel a bit more sticky. As soon as it will not slide easily off a trowel or shovel, it is too much. If it sticks to a trowel or shovel to begin with before any admixture, then there is too much clay and the bricks will probably crack. Then the soil needs more sand. There are whole books written about this such as the UN Handbook: "Soil-Cement, its use in building". See this page. Have fun."
-- ibid
4.
On prickly pear cactus goo:
"...If you have prickly pear cactus around they can be chopped up in a fifty-five gallon drum and left to percolate a bit. After a while a green sticky goo is produced that can be lifted out and added to mud to make a fairly waterproof plaster."
"..."I would say that you might cut up purple and green cactus and put them in separate five-gallon buckets and cover them with water. After a week or ten days they should ferment and if you keep stirring daily it should turn into a gelatinous mess. Then you lift out the mess with some fork-like device and leave behind the spines. The gelatinous mess can then be used to make plaster and I think around a pint per wheelbarrow is a ratio for starting. Maybe a quart. Every soil is different in how it reacts to admixtures.
Then you just have to scientifically monkey around till you find a mixture that can be troweled, does not crack upon drying, and demonstrates an enhanced resistance to water erosion. It will not be perfect, but if you can go from standard soil mixtures which have a one- to three-year life expectancy on a wall to a five-year or greater life, then you have made progress."
-- ibid
5.
Manure
"..."your use of horse manure is perfect. The closer to single fibers, the stronger the bond of straw to adobe. Big, heavy wheat straw is slippery and stiff and does not bond as well. Ancient cultures discovered it is a lot easier to let the horse do the work instead of chopping straw all day. Hassan Fathy thought that if the mud can sit for three days that the microbes present begin to make lactic acid which strengthens the adobe bricks. I am not sure this has ever been verified in a laboratory, but history is the best laboratory."
-- ibid
6.
Manure AND Cactus Juice
"For your water resistant plaster, the higher the clay content, the more resistant the plaster. For some reason, traditional wisdom tells us that cow manure is better for this water resistant plaster mix than horse manure. The Australians say, "the fresher, the better." In Northern Mexico and at Simone Swans in Presidio Texas there is interest in combining a little cow manure with prickly pear type cactus fermented in a drum for a period of time. The gelatinous goo is mixed in with the plaster at about a quart per wheelbarrow."
-- ibid
---
7.
More on asphalt emulsion.
The prices information is completely wrong by now. (This was written, I think, around 2005.) And the company in Albuquerque has a different name now. It's now called:
Wharton Dewwy
500 Tyler Rd NE
Albuquerque, NM 87113
(505) 350-7709
"Q: I was wondering how much asphalt emulsion is needed as a ratio to make mud cement and how much does a 50 gallon can of asphalt emulsion cost ..
"A: Each soil will react differently to asphalt emulsion so in New Mexico the definition of a stabilized adobe is a functional definition. That is, an adobe placed on a porous, water saturated surface for seven days may absorb no mare than four percent moisture by weight. Adobe producers will tell people that they use 2 to10 percent asphalt emulsion but do not mention if that is measured by volume or weight. I find that 8 to 16 liquid ounces is about right to stabilize a cubic foot of my soil's adobe mud. That is about 1/2 to 1% by weight. It is not fully stabilized but will give enough protection to preserve the adobe for my lifetime. Another way to add is to put 5 gallons of emulsion into a 55-gallon drum and fill it the rest of the way with water. That way the water has 10% asphalt. It is a little nicer to work with than full strength emulsion.
"The cost of 55 gallons of asphalt had been about $75 until the prices of oil products began to go up the last couple of months. My guess is that it is well over $100 by now. A source of emulsified asphalt in New Mexico is Elf Asphalt on North Edith Street in Albuquerque. Their minimum sale is by the 55 gallon container. You have to have your own barrel hopefully one with a removable top. Plan on splashing some asphalt on the cab of your pickup truck as a badge of honor."
-- http://www.greenhomebuilding.com/QandA/adobe/mixes.htm
8.
And, special bonus, some interesting facts about the paper we are using in papercrete:
- One three foot stack of newspapers is equal to one tree, approximately 30 feet tall
- One three foot stack of newspaper weighs 100 pounds.
- To make one ton of virgin paper uses 17 trees (3-2/3 acres of forest)/.
(Sorry, didn't record my source for those three facts.)
Hope this helps,
ken winston caine
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