Asphalt Emulsion Stabilizers

[M J Epko]

At 09:23 PM 10/6/96 -0400, Pat Newberry wrote:

>Yo I'm here!!!!

        Thanks Pat, and Willow too. I don't know what the problem was (or if
in fact there ever actually was one), but it seems to have cleared itself
up. Maybe it was just a touch of ergot in the bread.

>I heard that some folks put asphalt emulsion in there cob to stabilize it.
>is this the same as some foundation and roof coating which contain
>asphalt and Petroleum Distillate

        I have a book from the '40s called Build Your Own Adobe which
suggests just that thing - adding it to the adobe mix for waterproofing. I
seem to recall a post on the SB list recently saying that it is indeed the
same stuff used for roofing, that it's available in 55-gallon drums, and
that it's cheap.
        I suspect that this stuff would come in different degrees of
viscosity for different applications; the gallon-can I got for some roof &
gutter repairs last summer was like peanut butter, but the five-gallon
buckets of driveway sealcoater is like paint.
        From that book:
        "The emulsified asphalt we used ... named 'Bitudobe' ... from the
American Bitumuls Company. Many large oil companies also sell these
emulsions, or stabilizers as they are sometimes called. ...cost per gallon
is low and adds very little to the cost of the house...
        "... To determine [how much emulsion to add], build yourself a rough
box 12"x12"x12". Obviously this will hold a cubic foot and is as good a way
to measure that amount of earth as any we know.
        "Put enough [of your *dry* cob mix] in the box to fill it when
shaken down but not tamped in hard. Dump the [mix], so measured, in a trough
or metal wheelbarrow and dampen it [with water] ... add two quarts of
emulsified asphalt and mix it... until the whole mess is a uniform color.
Make several small sample bricks... and let them dry until hard.
        "When these specimens are dry, immerse them in a pail of clear, cold
water for six hours or so. (Shannon! - that's where I got that weird dunk
test thing from!) If the samples do not soften or discolor, the amount of
stabilizer is correct. If the sample bricks take up water or soften
appreciably, new ones should be made using up to three quarts of emulsion to
a cubic foot of dry [mix]."

        That said, I think I'd personally avoid using it - an unneccessary
expense and extra work - and instead design the roof with ample overhang,
providing small-but-usable sheltered outside storage, work and leisure areas.

>Does this mix with water.

        I wouldn't think so. Oil and water? Both are used in the mix, of
course, though. The book says that the idea is to coat the clay particles so
they don't take up water. Coating the sand isn't a concern because it
doesn't absorb water. So I suppose once a person had their proportions
determined, the clay soil and emulsion could be mixed, then the sand and
water added. Probably doesn't matter.

>I may add some portland cement to the earth plaster for the outside. 
>Any one know of any success with this.

        Isn't cement-based stucco the most common (though perhaps not the
best) exterior coating used? I'd think that a cement-stabilized earth
plaster would be fine, and has surely been done before.
        The cement would reduce the 'breathability', wouldn't it? But so
what. The rule of thumb is to have the less-permeable material on the warmer
side of the wall, right? - wouldn't that be the exterior down there in GA?
So you're okay anyway. I say it's a good idea, do it.

>Well let me know if anyone read this.
>I'll start my cob building in March or April

        I'll look forward to updates on that.
        We'll be putting our house on the market about that time, but want
to spend a year on the land before we finalize any building plans. We'll
probably live in our bus the first year, or maybe buy an old trailer house.
10x40s can be had in the area deeded, moved and blocked for ~$4000.



       M J Epko    duckchow at ix.netcom.com
        http://www.netcom.com/~duckchow/