[lifesaviors] Fiber-reinforced building techniques
- From: "Lion Kuntz" <lionkuntz@xxxxxxxxx>
- To: "Art Krenzel" <phoenix98604@xxxxxxxxxxxxx>
- Date: Mon, 21 Jul 2003 22:31:45 -0800
Hi Art
Sooner or later, if I intend to be part of promoting my ecocity ideas, I will
be asked serious questions. You asked good questions, and I hope you don't mind
if I use you to rehearse my answers for when the day comes that I am expected
to have answers.
Near the end of the Ecocity e-conference I did a back of the envelope
calculation for concrete costs. I don't like nasty surprises so I try to work
with very conservative figures -- then if anything pops up, the wiggle room is
already factored in. I used steel reinforced (rebar) slabs and walls and came
up with a figure of about $450,000, which was not bad divided by 118 units.
People would have been charged, pro rata $4k for concrete at US wholesale
delivered prices per residential unit. Meanwhile, I ran some other numbers and
computed that fiberglass rebar concrete posts could do most of the loadbearing,
with some judicious use of expensive materials.
Well this time the numbers came down: concrete posts and hydralically-pressed
earth bricks for infill can build 18 feet of wall, ten feet high, and consume
ONE SACK of portland cement. Each earth brick itself (having been pre-squashed
at 100,000 pounds of pressure) has a loadbearing rating of 1,000 pounds per
square inch, or 140,000 pounds per brick measuring 10 inches by 14 inches. This
is one-third the compressive strength of 3,000 psi concrete. That 18' brick
wall is rated to carry 1,050 tons, not counting the triple strength of seven
posts (3 ksi) spaced one every yard (or meter).
Since 3.33 cubic yards would have been consumed (plus all that rebar) at US$150
per yard, and $166 of concrete has been replaced with less than $10 worth of
concrete, suddenly using very expensive strengthing materials in small
quantities. Some carbon fiber ties and rebars suddenly become an affordable
detail, and still the cost is lower.
I went through the 8.1 quake in SF in '89. A few months later in Mexico city
they had a 7-something that pancaked lots of residential projects. I don't want
to be in a building, or read about a building I helped design, that killed
people.
There are new illustrations queued up for posting on my website which tell the
step by step details of building a palace that will ride through intact from an
8+ quake.
That 18' feet of wall takes 450 earth blocks, a half-hours production from
AECT's deluxe machine (900 blocks per hour), uses one gallon of diesel in half
hour. The blocks go up in 15 minutes using two unskilled workers (2,000 blocks
per hour, rotating teams every two hours).
In a multistory structure, at progressively higher floors the strength
considerations become decreasingly important, so switching from carbon fibers,
aramid fiber and e-glass becomes the intelligent thing to do. At every level,
decreasing the weight descreases the strains below, so there could be
justification for using more expensive materials in upper floors also. That's a
matter of doing what-if computations and steering a course which gets the most
bang for the buck.
Here's the back of the envelope computations on that 18 feet of wall: 18' was
determined by the amount of cement in one 94 lb. bag, could make 7 posts 3.5"
by 10'. $8.55 of concrete (including purchased sand and aggregates for posts.
$10 fiberglass rebar, $15 block laying labor. The earthblocks cost whatever the
machine costs divided by its productive lifetime output, labor to operate,
labor to keep the hopper filled. The machine uses 2 gallon of fuel per hour,
$2.00 per half hour. The critical issue appears to be earthblock machine, and
operation expenses. If the earthblocks are half of concrete blocks (say $0.50
each, than it is $225 for 450 bricks, higher than using steel-reinforced
concrete.
By comparison, a concrete posts and octet truss wall, can be formed on a
backboard form with shotcrete in the same half hour to a thickness of 4".
Double ultimate strength, much lower materials costs (@ $0.50/brick). Better
water-proofing (shotcrete is used in swimming pool construction). Ultimate
labor costs include sprayer and forms building. Much higher CO2 impact. The
most critical issue is the cost of disposal of excavations on the site. If the
trucking figure is high, and a significant tipping fee is charged, it may be
cheaper to dispose of the excavation dirt as building materials within the
building itself. However. a majority of the excavation may be unsuitable for
building use, and the building cannot absorb beyond a specified limit.
Shotcrete is highly beneficial in ground-floor exterior walls in every location
where flooding is a possibility.
If it becomes desirable to build with earth blocks, then there exists a
practical plan for using them in a manner which is strong and safe. It uses a
spectrum of materials and techniques, from space-age materials to stone-age.
On the other point you brought up: the Octet Truss has very few internet
references. It simply is not understood or used, so there are no test results
from anybody on Octet reinforced concrete, fiberglass wrapped or not.
Steel and concrete buildings use a corrigated or ribbed steel decking, upon
which a slab is poured. The strength to weight ratio of the steel reinforced
concrete determines the distance between supports. Steel is not a suitable
material for use in 100-year lifespan buildings. It rusts, swells, cracks the
concrete, and ultimately fails. Internally this process is retarded
considerably, but used in weather barrier walls and decking, it does not last.
In modern business it lasts long enough so that everyone who profitted from
constructing the building is long gone as it dies.
Steel is energy intensive, as is portland cement. Glass, aramid or carbon
fibers are also energy intensive, but the carbon is five times stronger at one
quarter the weight in a similar conformation (say "I" beam of certain length,
width and height). That is a multiple of 20 times savings: lower weight means
lower strains on supporting members, higher strength means do more with less.
Steel softens in a fire, bringing down the concrete and steel. So reducing the
weight by using carbon, and using geopolymer, means that a lighter load can
span a greater interval between supports. The supports cost money and the load
supported costs money. But it is not just the materials costs.
Steel fabricated buildings are a capital-intensive operation. The parts in my
building are designed to snap together like lego blocks, and reduce the labor
costs and especially the capital-intensive labor costs (crane operators, iron
workers). The reason I decided on 3.5 inch diameter posts, after looking at all
sizes in half-inch increments up to 12", is because at 100 pounds two workers
can carry it from the truck to position and raise it vertical without
equipment. Each post can bear a rated 14 tons. A 10 foot 2"x4" made of
octet-reinforced concrete weighs 75 pounds. The weight of the reinforcement is
a trivial issue compared to the strength, and safety issues.
The parts can be made in a climate-controlled factory (actually a Palace ground
floor is ideal, with ample solar thermal for curing kilns). Everything is
modular, truckable, gender-friendly construction. For most building assembly
jobs it takes 15 minutes training unskilled workers what to do. That applies
both in parts fabrication in the workshops as well as on-site building
fabrication.
Considering the large number of Palaces required for 100 ecovillages, or 1,000
ecocities, it is a good thing they use such thoughful labor-intensive methods.
I was stumped on how to make the sewage treatment water-reclamation operate
without moving parts: all solid state, and gas/water pressures. I solved it
during writing this letter. Did you like the water distribution scheme I
illustrated? The sewer water scheme uses (some of) the other part of the water
electrolysis -- the oxygen "waste product". Want to know how it works? I need
to know if my explanations are getting through. I use graphics-heavy
illustrations because there was an international audience in the ecocity
e-conference. I'll put up some pictures of the sewer thing in a while -- my
backlog of "to-do" is stacking up.
-- Later
Lion Kuntz
----- Original Message -----
From: "Art Krenzel" <phoenix98604@xxxxxxxxxxxxx>
Date: Sat, 19 Jul 2003 09:34:21 -0700
To: "Lion Kuntz" <lionkuntz@xxxxxxxxx>
Subject: Re: Testing, 1, 2, 3....
> Lion,
>
> I can certainly help you on patent searches. I just put the finishing
> touches on a patent yesterday and sent to the Patent and Trademark Office.
>
> I have good friends who are in the model aircraft racing business and are
> all "wrapped up" in carbon fiber. They have told me that the most
> economical fiber for beam construction is e glass. Carbon fiber is used
> because they have gone well beyond the concept of economy and are working in
> the arena of "win at any cost". In a cost/benefit evaluation, the low cost
> but medium strength of e glass makes high volume construction an economical
> venture. The use of carbon fiber in such a low tech, high volume
> application such as building beams renders the final product too costly for
> use by the general public IMHO.
>
> I downloaded some information from the links you provided last night and
> read more information on Geopolymers. I did not read enough information but
> became very interested in Indigenous Materials. I love things with no
> moving parts, low cost and indigenous.
>
> In my discussion, I did not tell you that I have a hydraulic press with 20
> ton capability and a skid steer loader to make the movement of heavy objects
> a breeze. I feel that everyone should have a skid steer loader or fork lift
> to take the grunt out of life.
>
> It would seem that the Civil Engineering Societies would have already done
> some of the testing on the fiberglass coated beams but I have not searched
> as yet and do not know. They made quite a big deal out of coating all the
> concrete supports with fiberglass some years ago on the freeways in San
> Francisco to prevent the explosion of the concrete on overload. Did you
> follow that?
>
> I am glad we re-connected.
>
> Art Krenzel
>
--
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