Straw Bales as Concrete Void Form for Garage Floor
Wpg Man
form" for a concrete garage pad?
Typical garage pads in my area are made on top of a gravel base that
is deeper around the edge. This gives a one-piece concrete pad that
is "thickened" around the edge for strength. These pads are pretty
good, but they are only "thickened" around the edge and can still
crack.
I want to dispense with the gravel completely, and use hay bales as a
"void" form as follows:
Place bales in a series of solid 8ft x 8ft squares on the ground.
Between each set of 8ft squares would be an 8 inch gap. If you can
imagine, the concrete is poured over the while thing. The concrete
would go down into the 8" gaps, giving an integral concrete "beam"
every 8 feet. So instead of a "thickened" edge beam only, this pad
would have a matrix of beams every 8 feet. Of course there would be
rebar also.
The hay bales are basically there to "save money" on concrete (instead
of pouring a 2 foot thick floor). I think this floor would be so
strong that you could lift one corner and the whole thing would stay
together (no cracking due to frost etc).
I am wondering about these hay bales though. I really don't care if
they rot after the concrete sets. Does anybody see any problems? I
would probably put plastic on top of the bales to seperate them from
the concrete. Do you think I should also put plastic underneath them
so they stay dry forever?
I think the cost would be less also. Typically, you need 2 feet of
gravel under the floor to raise the grade of the garage floor. With
the bales, I automatically get a 2 foot raise in the grade, as well as
the extra strength from the beams.
Also, if you really want to go nuts, the beams can be made deeper (or
the grade can be raised) with very little cost by stacking bales on
top of each other. If you were to stack 2 bales (instead of one), the
beams are deeper and it would not take much extra concrete.
I also like the fact that the beams (both in the middle and around the
edge) are nice and "square". The "thickened edge" garage pad has a
beam around the edge that is formed by the sloping gravel beneath it,
giving a "not so pretty" beam.
Thanks.
tonyg
would be better off using concrete with extra rebar. tonyg
----------
In article <6b65e7e9.04040...@posting.google.com>,
Mike Dobony
"Wpg Man" <wdo...@yahoo.com> wrote in message
news:6b65e7e9.04040...@posting.google.com...
What you are describing is a bad way of making a structural concrete garage
pad like a parking ramp construction. Bare in mind that these structures
are heavily reinforced with pre-tensioned rebar and high strength concrete.
It takes special knowledge and skill to do this. you risk having your car
drop 2 feet into a hole when, not if, your floor fails. Stick with gravel
and go with a 6" pour instead of the standard 4" and go a good 10" around
the perimeter for an integrated footing.
--
Mike D.
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Trai' La Trash.
I've seen it used for walls but not floors.
If you want to save just backfill with old material.
Nehmo Sergheyev
> Does anybody have any thoughts about using straw bales as a "void
> form" for a concrete garage pad?
- Nehmo -
Crushed stone of the type you use under concrete in Kansas City runs
about US$25/yard^3 delivered. It's about the cheapest thing there is.
--
*********************
* Nehmo Sergheyev *
*********************
SQLit
So what is going to hold the concrete up when the bales decay? Please send
pictures when you do this and the failure that will surely happen.
DanG
Sounds like a carton form slab.
It was suggested as an option on a high plastic index job. We
elected to use lime slurry injection as a less expensive option
that project.
I never got into the details of designing the bearings for that
slab.
Carton forms are usually used to create expansion voids under
grade beams. I know that hay was used for this void in the past,
so your idea has merit. I would guess you simply need a strong
enough slab to span the voids.
Waffle slabs have decks as thin as 2", though I would tend more
toward a thicker slab. Post tension might be considered.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Keep the whole world singing. . . .
DanG
"Wpg Man" <wdo...@yahoo.com> wrote in message
news:6b65e7e9.04040...@posting.google.com...
Eunoia Eigensinn
Straw-bale-formed waffle slabs have been used on a number straw bale homes,mostly
in Quebec, so it is something that has been done. The intention was that the
straw bales would serve as insulation, as an alternative to foamed plastic
insulations.
There have also been forensic studies done on the above slabs (when they were
about 10 years old) and as you would expect, the straw did show signs of decay so
you should not have any expectations for the straw be there permanently.
Without doing any number-crunching, my wild-ass guesstimate would be that the
slab between the ribs would need to be at least 200 mm thick, with reinforcement
designed for 2-way action (ie Lots of engineering calc time + lots of time
placing reinforcement)
I also think that the bottom line would be that an unreinforced thinner slab,
(non-waffle) cast on compacted crushed stone fill would likely be more economical
and just as serviceable.
Wpg Man
you think I'm crazy, he he).
Your description of a "waffle" was just what I had imagined. If you
were able to look up (from below) it would look like a "coffered"
ceiling.
Yes, the biggest concern is the strength of the slab between the
beams. Of course that would require an engineer. However, I can't
imagine a problem with an 8x8 ft slab. I've seen lots of untensioned
8 foot spans (for example in small "man" tunnels under roadways etc).
As for gravel. A 24x24 garage pad with 2 feet of gravel requires
approx $1000 of gravel. If you don't want to break your back tamping
every 6" of the stuff, it's gonna cost another grand for the labour.
The hay bales would cost almost nothing (less than 100 bux, or you
could scrounge some for nothing). I think the labour is less with the
bales (still a bit of work though). Even if the cost of gravel were
"zero", I hate the results because any settling or frost just cracks
the slab. I want that sucker so strong that you could flip it over in
one piece.
Mark my words, I will start a revolution in the construction industry.
Soon we will see office towers constructed with the "hay bale"
method!
"DanG" <dgri...@7cox.net> wrote in message news:<sOQcc.101$6y6.81@okepread03>...
> Sounds like a carton form slab.
>
> It was suggested as an option on a high plastic index job. We
> elected to use lime slurry injection as a less expensive option
> that project.
>
> I never got into the details of designing the bearings for that
> slab.
>
> Carton forms are usually used to create expansion voids under
> grade beams. I know that hay was used for this void in the past,
> so your idea has merit. I would guess you simply need a strong
> enough slab to span the voids.
>
> Waffle slabs have decks as thin as 2", though I would tend more
> toward a thicker slab. Post tension might be considered.
>
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> Keep the whole world singing. . . .
> DanG
>
>
> "Wpg Man" <wdo...@yahoo.com> wrote in message
> news:6b65e7e9.04040...@posting.google.com...
> > Does anybody have any thoughts about using straw bales as a
> "void
----SNIP
Trai' La Trash.
Nehmo Sergheyev
- Nehmo -
For those of you who didn't follow the link, it leads to a site selling
metal-frame tents and frameless covers that can be used for garages.
But the way I see, OP can make a box about the size of a bale of hay,
with one side angled. The opposite side can also be angled but it would
be movable like a piston. Place a bale of hay in the box and use a
bottle jack to push the piston and compress the bale. The product would
be a bale in a truncated-wedge shape (a cross-section would be an
isosceles trapezoid).
With these bales and some regular bales, OP can assemble an entire
barrel-arch garage!
Eunoia Eigensinn
Nehmo;
Nice idea but the reality is that straw bales alone are not really a material
that is suited to pure compression structures like domes or vaults.
While it is true that straw bales are strong in compression and it is possible to
build straw bale vaults, vaults built using bales alone (in the manner you
describe) tend to collapse eventually, and in a spectacular fashion.
The problem is perhaps best understood by looking at a masonry arch. As you may
be aware, it is possible to erect a masonry arch leaving out the mortar in the
lower half of the joints and have the arch remain in the air.
When using bales compressed into trapezoidal wedges, the most highly-compressed
portion of the bale is in the zone which would experience next to zero
compressive stress. Moreover, as "an arch never sleeps" the portion of the bale
under compression will continue to compress, ultimately leading to collapse of
the vault or arch.
As mentioned, straw bale vaults have been built and have been approved by the
Code authorities in California, most notably the one built for the late
musician/composer Lou Harris, by Skillful Means Construction (see www.skillful-
means.com ) and one by Mikal Jakubal.
Images of the Jakubal vault can be seen at the SB-r-us Yahoogroups site, in the
PHOTOS section.
http://photos.groups.yahoo.com/group/sb-r-
us/lst?.dir=/Vaults&.src=gr&.order=&.view=t&.done=http%
3a//photos.groups.yahoo.com/group/sb-r-us/lst%3f%26.dir=/%26.src=gr%26.view=t
and also at
http://www.asis.com/~edexpert/strawbale
Eunoia Eigensinn
> Thanks for the reply, and thanks to all others that replied (even if
> you think I'm crazy, he he).
>
> Your description of a "waffle" was just what I had imagined. If you
> were able to look up (from below) it would look like a "coffered"
> ceiling.
>
> Yes, the biggest concern is the strength of the slab between the
> beams. Of course that would require an engineer. However, I can't
> imagine a problem with an 8x8 ft slab. I've seen lots of untensioned
> 8 foot spans (for example in small "man" tunnels under roadways etc).
>
> As for gravel. A 24x24 garage pad with 2 feet of gravel requires
> approx $1000 of gravel. If you don't want to break your back tamping
> every 6" of the stuff, it's gonna cost another grand for the labour.
> The hay bales would cost almost nothing (less than 100 bux, or you
> could scrounge some for nothing). I think the labour is less with the
> bales (still a bit of work though). Even if the cost of gravel were
> "zero", I hate the results because any settling or frost just cracks
> the slab. I want that sucker so strong that you could flip it over in
> one piece.
Why ? Are you in the habit of flipping over concrete garage floor slabs ?
> Mark my words, I will start a revolution in the construction industry.
> Soon we will see office towers constructed with the "hay bale"
> method!
I'm not going to hold my breath waiting.
I think that we'll see Iraqi Saddam Hussein loyalists hugging/kissing Americans
before we see any office towers constructed with the "hay bale" method.
However, about 30 years ago in Quebec, the walls of about 20 homes were built
using 3"-thick concrete joints (horizontally and vertically) between the straw
bales, creating a structural concrete grid of columns and girts. The description
of their construction is available from the Canada Mortgage and Housing
Corporation. www.cmhc-schl.gc.ca
Wpg Man
Again - thanks for all the replies. I'm getting the distinct
impression that you guys are not too hot on this idea!
Anyway, I notice a few of the responses refer to the bales not
providing enough support. I just want to make it clear that I do not
intend for the bales to provide any support. They are simply a void
form. A cheap way to displace the concrete while it cures. I
wouldn't care if the rotted away (in fact I would prefer it). I was
even pondering some method (chemical disolving or fire) to get rid of
the junk after the concrete sets. I only see them attracting rodents
and moisture later.
Eunoia Eigensinn <Eige...@BVI.com> wrote in message news:<1104_10...@news.vif.com>...
------SNIP
> under compression will continue to compress, ultimately leading to collapse of
> the vault or arch.
>
-----SNIP
Trai' La Trash.
> Hi
>
> Again - thanks for all the replies. I'm getting the distinct
> impression that you guys are not too hot on this idea!
>
> Anyway, I notice a few of the responses refer to the bales not
> providing enough support. I just want to make it clear that I do not
> intend for the bales to provide any support. They are simply a void
> form. A cheap way to displace the concrete while it cures. I
> wouldn't care if the rotted away (in fact I would prefer it). I was
> even pondering some method (chemical disolving or fire) to get rid of
> the junk after the concrete sets. I only see them attracting rodents
> and moisture later.
>
What ever happened to a good'ol back fill? I'm pouring another slab on
block and throw anything solid in the hole. Old lollie poles,scrap block
rocks ect.
nicks...@ece.villanova.edu
> Place bales in a series of solid 8ft x 8ft squares on the ground.
> Between each set of 8ft squares would be an 8 inch gap. If you can
> imagine, the concrete is poured over the while thing. The concrete
> would go down into the 8" gaps, giving an integral concrete "beam"
> every 8 feet. So instead of a "thickened" edge beam only, this pad
> would have a matrix of beams every 8 feet. Of course there would be
> rebar also.
How much rebar in the (20" deep?) beams and 8'x8' slab, if
it supports a 4,000 pound car? How thick would the slab be?
Nick
Marc
something that decays under concrete is a really bad idea! Generally when
pouring concrete you try to remove any organic matter, not add it!
To be honest i am not sure what you are trying to construct, but how about
something that doesn't degrade like polystyrene (plus don't forget some mesh
reinforecement!
Marc
"Eunoia Eigensinn" <Eige...@BVI.com> wrote in message
news:1105_10...@news.vif.com...
Don
I think the straw is amazing. My dad used to use bales of straw to dummy up
porches for a concrete pour. Long as it has lots of rebar in it he said it was
good to go.
--
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god
--
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Tekkie©
On Fri, 11 Jun 2021 20:45:02 +0000, god posted for all of us to digest...
>
> I'm seeing these all over now, and they are calling them Wpg-slabs. Seriously, though, as a structural engineer, I wanted to flesh this out, as it is a primary return on google. These are called waffle slabs, and they have been used for this application all along. They usually use something like a plastic bucket as a form
(https://www.geoplastglobal.com/en/products/slabs/skydome/). Floatation is an issue with both the form voids and your hay. Your settlement is much higher with the waffle voids made of "hay" (straw) than if they were soil, but you design the slab to span the void. Using hay in scenarios like this is somewhat common, but not for
careful formwork as you describe. The main reason is that hay has zero lateral pressure, so you can temporarily fill a void (it will decay) without a temporary condition with substantial earth retention pressures when casting structural concrete slabs, where it is a big no-no to leave that as a void. I was here looking for what
vermicide to add.
--
Tekkie