On Sep 25, 2007, at 9:46 PM, aws aruba_workshop wrote:
> [The blocks were light] do you have an estimate about the weight of
> your 15"x15"x4"
> What is the reasoning abou using 15"x15"x4"?
> [ with a mix of 1:1 cement / paper] is this by weight or volume?
> do you remember how much water you used?
> What is the reason you do not want to use the plans for your fences
> and blocks?
> How do you apply the prickly pear in the mix?
> Do you have an idea about the working/function of the prickly pear
> in the mix?
> What is the reasoning to reduce the cement content of your blocks?
> Do you have an idea about the working/function of the cement in the
> mix?
We were hoping to achieve near R-50 insulation so a 15" thickness
sounded about right for the block. We had a lot of salvaged 2x6 wood
so a 4" height seemed about right after shrink. A bigger block would
have made more sense. Our blocks only weighed in at 6-8lbs.
The 1:1 cement/paper measurements are based on dry weight of paper
and cement. Not by volume.
Our water usage was about 100 gallons to 60 pounds of paper and 60
pounds of cement.
The structural engineer approved block wall/fence plans was scrapped
because of the amount of cinderblock, concrete, and rebar. Plus all
the work of making blocks, waiting for them to dry and moving them
about the property in various stacks. It has been a wet year for New
Mexico all of our block and slab work had been greatly slowed due to
the weather. All that and we got into ferrocement and realized that
was a lot easier to build structures that look very professional and
take well to papercrete infill and stucco.
We have only used prickly pear in our stucco mix. We grind the
paddles in our tow behind mixer and filter out the cactus needles/
fiber with lath. This leaves us with buckets of slime. I've been
adding a gallon of the prickly slime to each 5 gallon bucket of our
stucco. The stucco mix I like the most so far is:
- half a 5 gallon bucket strained PC
- 1 gallon of prickly pear slime
- 4 cups of lime
- 2 cups of portland
- 2 cups of micro silica
I can see the prickly pear drying just like elastomeric paint. This
is easily shown in the plastic we layout to catch all of our misfires
while spraying the stucco. We get smooth rubberish sheets of PC that
have a elastic quality. I see the exact same thing when using
spraying elastomeric paints. The prickly should also function as
sealant, anti-bacterial, flame retarder and coloring agent.
Cement gets expensive in the 1:1 ratio. I'd rather increase sand,
clay, and prickly which I can buy by the ton for the same price as a
bag 94lb bag of cement.
I've played with my cement levels quite a bit. I've found when
working with only paper and cement with no other additives it is a
VERY bad idea to go below a 1:1 ratio by dry weight. The blocks are
weak and will fall apart within a year full weather exposure. They
are also quite flammable.
> I would like your opnion/ educated guess about the use of
> 2 metal roofing corrugated irons [ in your case 15" wide] vertical
> placed with reinforcement [can be 2x4 lumber ] placed on an elevated
> base of mesh wire [about a litte more than 4 " wide] as forms for
> your blocks.
> in this way you also can stack these molds horizontally so you use an
> corrugated iron on both sides.
>
> if there is enough airflow the drying time should be reduced and can
> further be reduced by making use of vibration that works two ways as
> dryer but also as compactor and/or an industrial size fan.
>
> in this way the blocks can be larger i think about 2 or 3 feet long
> and can easy be placed on each other i suggest. can you eleaborate on
> this line of thinking?
I'm a little skeptical of this PC mold idea. The corrugated roofing
irons would not let much air pass which could slow down drying. The
mesh wire for drainage can be tricky. My PC mixes were always so wet
that it would take a lot of material to not pass through most forms
of mesh. I don't see how you can have fine control over block
dimensions without a form of compression. If the blocks are not keyed
or cored there will be reinforcement and alignment issues to deal
with during construction. I do like the idea of big blocks. It is not
clear to me how you would get these large blocks out of a raised
form. Also how many could you make a day? I made 200 lousy blocks a
day with some a single 2x6 ladder form. The dry time was still about
2-3 hot dry days before they could be transported and stored for
later usage.
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