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My tried and true Formula for building with stabilized adobe block:
Bonnie's tried and true Formula for making stabilized adobe block.
The building is 20' x 16', and the blocks are 12"x16"x4". Walls are 12" thick.
The walls are of stabilized adobe blocks. These are made with adobe dirt, with a little sand and cement
added. 7 adobe dirt to 1 sand to 1/2 portland cement (parts) for the blocks;
For the mortar: For the bottom layers, I used 9 to 10 parts adobe dirt, 6 parts sand, 2 to 3 parts cements. note:
the mixing of dirt/cement with dried clumped dirt is virtually impossible, requiring the premixing of the sand/cement
with water as also soaking the adobe dirt with water also. Then mixing the two wet mixtures together.
(Adobe dirt requires a long soaking however, due to the clumps of clay, by hand that is. A mortar
mixer would be the most effecient way to mix it.) There are no plans to stucco the walls, and the adobe blends
in beautifully with the type of terrain surrounding it.
For the top layers, (half way up and higher) I lowered the amount of cement, and
towards the top, I quit adding cement to the mud except for where the blocks are resting on
the header above the windows and door. But where I used cement, I soaked the dirt with water for
several hours in a wheel barrow, then when it was the right consistancy, (not too runny),
I mixed about 1 shovel or less, of cement with water separately, and then added this to the wet wheelbarrow
full of mud. This way the mud dries harder. The mud works better without or
with less cement, and you do not have to worry about finishing off the entire batch so soon if you don't
use any cement.
To find the perfect adobe dirt, with some research and a friend's notes, one
can test the adobe dirt to see if it will be pass the test, by putting the dirt in a jar with water, let it sit for awhile
to soak, then shake the contents and let it settle in layers. Ideally, I'm told, this is the percentage
of fine, course, silt, and clay, making up the adobe block (unstabilized with cement).
19 % Course sand
42 % Fine Sand
22 % Silt
17 % Clay
3 % Colloidal
Around Terlingua and other areas in the Big Bend, Texas, there are locations that have naturally occurring ready-to-use
adobe dirt. However, much of the area consists of the wrong type of clay, such as bentonite clay, which is
a very high absortion clay, therefore high rate of cracking would occurr in blocks. Some ranches have, historically,
dug good adobe dirt in areas, where there is no foliage growing, and by digging a small pit, water drains and accumulates
there, and grasses or plants begin to grow, where previously would not.
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