Structural Slab for new WFO

[mikku]

Re: Structural Slab for new WFO

Laurentius,
Thank you for your input as always!

The guy you used has to be a lot brighter than the "local distributor of masonry stuff here" or you have to be a lot better at Eigo-Nihongo than you claim.

The translation for lime- is: a citrus fruit, an agriculture additive, white powdery substance, component of drywall. Nothing to indicate qualities of water proofing, texture altering, adhesive qualities, component in masonry construction. So I do come across as "baka gaijin!" (crazy or stupid foreigner for those w/o Japan vocabulary)--sometimes worse if combined with other words!

Maybe your Japanese assistant knows what is in the "little plastic baggie" that the masons use! Probably not lime, but something with similar characteristics? Could you ask him--next time you see him? He had to use something for preparing the mortar for your firebrick work. Maybe he can give a "kanji", all I get is some kind of "sekkai" and that is recognized as the "lime for changing Ph in soil.

This is "all for information purposes only" - Passed the need to know phase.

[mikku]

Re: Structural Slab for new WFO

Out with the new and in with the old and stronger!

My fabricator delivered his contribution to my build--old wheels to carry the oven load! Photo: 122kg max/wheel vs 460kg max/wheel. This should make moving this inside the garage easier & safer. He also brought news on the chimney--I am looking at around Y9500 for my home-fabricated stainless chimney! Around $100 US! Have to go with it--in budget!

Decided on oven- It is going to be an igloo! No fancy, bells and whistles. Perlite insulation 4" thickness-scratch coat of some type of home brew plaster, finish coat of "shikkui", off the shelf "plaster coat" white colored--used a lot on old homes, castles, fences--I think that it has hemp fiber or some other natural fiber to add crack resistance! It is supposed to be water-resistant if not proof?

Also started insulating and had a fun day working in the mud. The fancy angles and joints mean nothing once covered!

Maybe this oven will see fire by the end of the month!

[mikku]

Re: Structural Slab for new WFO

Pericrete technique: Fairly dry pericrete mixture, use a rubber float to hold finish surface-other hand place loose mix in place, press a little and hold. Keep working in rings. When high enough or when the surface feels firm, run the float across the surface to shave high spots--also can fill in lows.

I used a small plastering trowel to clean up the bottom edge and lightly touch up the surface. It seemed a little harder--did not want too smooth.

Only used my hand width as gauge of insulation thickness.. If someone wants it done better, they can do it themselves! This is close enough for me. Tomorrow will finish covering the dome and bring insulation to base of chimney vent--no chimney for 3-5 days!

Everytime I play with new materials, I am surprised with the shape hidden in the pile of materials. Work it a little and fun things pop out. This same thing happens with pieces of wood. Cut, sand, plane, route da, da, da and a house pops out, or a chair, boat, ... really never know what is hiding in the pile of material until you start working with it! That is why I like working with my hands!

[david s]

Re: Structural Slab for new WFO

Good job Mikku,
I hope you kept the mixture lean as cement reduces the insulation value enormously.it also takes LOTS of water, about one third of the volume of perlite approx. and that water needs to be removed before you do the stucco layer.

[mikku]

Re: Structural Slab for new WFO

10:1, Didn't think I had the ability to try larger ratios.
I have the dome covered in plastic for the night, hopefully for the small amount of portland to---set??

I saw a post somewhere about using a high wattage quartz lamp to bring up temps inside the oven to drive out water.

Any other suggestions for a drying out? Garage temperatures 24/7 @ 19degC.
I can change that by simply turning up the thermostat, but that is going to cost more in kerosene to run the boiler for floor heating.

Thank you for the information and watching this thread!

[mikku]

Re: Structural Slab for new WFO

For stucco layer, are you meaning "any cement type coating" including the scratch coat, OR just the final coat that essentially waterproofs the job?

[david s]

Re: Structural Slab for new WFO

For stucco layer, are you meaning "any cement type coating" including the scratch coat, OR just the final coat that essentially waterproofs the job?

I meant any cement layer. Removing the water without the assistance of sun and wind is going to be problematic.

[mikku]

Re: Structural Slab for new WFO

Well, that is going to mean--getting those "old wheels" bolted on and moving the assembly near the garage door opening. I have a southern exposure so the doors get opened for the mornings--

Get the drying effect from Sun and some of the dust can get blown out of the garage or vice versa. Not the same wind or sun as outdoors, but always dry.

So--this is one of the down sides of pericrete.
Thanks for the warning.

Off the wall thought.. Your seasons are opposite of the Northern Hemisphere Continents, do you typically face buildings to the North for sun exposure?

[david s]

Re: Structural Slab for new WFO

[QUOTE
Off the wall thought.. Your seasons are opposite of the Northern Hemisphere Continents, do you typically face buildings to the North for sun exposure?[/QUOTE]

yes that is true for southern Australia or colder regions. We live in the tropics and are not looking for any extra sun, even in the winter.

[mikku]

Re: Structural Slab for new WFO

That is very interesting!
I have always lived in a cooler climate, northern hemisphere, utilized direction for solar gain, morning sun to help usher in the day, evening sun to usher out the day--recreation spaces south/west to keep insects at bay.

Some here do planning of structures-all based upon orientation North/South, something to do with luck or superstition????. But do not know the "word" something like "fu-su-ee". Actually shows up on architects' building permit application!

Also never realized the size of Australia.. Thanks for the lesson!
Is it true about the direction water swirls as it goes to drain--different in hemispheres as well?

[david s]

Re: Structural Slab for new WFO

That is very interesting!
I have always lived in a cooler climate, northern hemisphere, utilized direction for solar gain, morning sun to help usher in the day, evening sun to usher out the day--recreation spaces south/west to keep insects at bay.

Some here do planning of structures-all based upon orientation North/South, something to do with luck or superstition????. But do not know the "word" something like "fu-su-ee". Actually shows up on architects' building permit application!

Also never realized the size of Australia.. Thanks for the lesson!
Is it true about the direction water swirls as it goes to drain--different in hemispheres as well?

Yes the water does drain the other way in the southern hemisphere. Cyclones also rotate in a clockwise direction unlike hurricanes in the Nthn. Hemisphere which rotate anti clockwise.
Where we live nobody likes the prospect of introducing daylight saving. We are happy when the sun goes down, for us it's just heat saving.

[mikku]

Re: Structural Slab for new WFO

That is worth a good chuckle!

[mikku]

Re: Structural Slab for new WFO

Progress on insulation.



That is far as I can go without a chimney!
Tried to make the top of the dome insulation thicker- but now it looks like one of the "cone heads"! A few bumps and dips--but better than I expected from eye-balling it only.
Just have to call it character!

I was surprised, this morning I was able to shave some of the edges using an OLFA cutter. The insulation is still very fragile, but it cut like styrofoam.

There are places where this stuff is over 6" thick--(near the inner door opening), lots of water to dry out!

[mikku]

Re: Structural Slab for new WFO

Question time again:

1) I have been warned about getting all the water out of the insulation prior to rendering.

2) Today, the insulated pericrete dome when tapped returns a hollow type sound.

3) I did not clean out the wheelbarrow used for mixing yesterday--but the dry stuff left from yesterday shows no properties of firmness--simply crumbles if you roll it around in your hand. But that material was not pressed into place or tamped in any fashion.

4) Yesterday, when adding the second level to the dome, I wet the dome--and you could visibly see it absorbed into the refractory... the water placed on the previous days pericrete--simply disappeared with no sign of color change from absorption.

Here are the questions:

1) Does this pericrete reach an "ultimate strength" after a certain number of days?

2) If so--by experience, how many? Like concrete approx. 28 days?

3) Will it develop a structure where I do not have to be careful about bumping it without fear of it crumbling to powder?

4) Given the fact that this material is extremely porous, and that a render coat will re-introduce a significant amount of water... and the strength of the render will be dependant upon a slower dry (for hydration)... would it not make sense to do the render sooner, rather than later BUT leave a significant opening...like Gulf describes for venting moisture?

5) I am dealing with a slightly mobile build--I worry about jacking up the slab to install the wheels--and any vibration to the slab by moving... I really don't want a chunk of this insulation to fall off like an egg shell!

6) The other upcoming event will be a curing fire--so far "done outdoors" unless I use the "propane fire ring" technique or "heat beads" with the garage doors open. Both techniques, however, require a final burn using wood to get the high temps. This would involve moving everything outdoors via forklift and possible-bumping, twisting, etc. forces---that a render might protect!

My structural slab is quite rigid--visibly at least, if the base is not supported equally, it will rock rather than flex.. But this pericrete seems very brittle!

Only someone who has worked with pericrete can answer these questions because they have actually observed the characteristics of a 10:1 mix as it is installed and as it ages!

I can see no reason for anyone to build up pericrete in 1" layers over a dome!
I saw on another website, someone advocating the use of lime with portland & vermiculite/perlite --only reason I can see would for it to adhere easier in thin coats...But this would also decrease the insulative properties?

Sorry for the "longwindedness" but a lot of questions requiring answers.
Also must evaluate risks vs advantages in the build!

[david s]

Re: Structural Slab for new WFO

.

Here are the questions:

1) Does this pericrete reach an "ultimate strength" after a certain number of days?

2) If so--by experience, how many? Like concrete approx. 28 days?

3) Will it develop a structure where I do not have to be careful about bumping it without fear of it crumbling to powder?

4) Given the fact that this material is extremely porous, and that a render coat will re-introduce a significant amount of water... and the strength of the render will be dependant upon a slower dry (for hydration)... would it not make sense to do the render sooner, rather than later BUT leave a significant opening...like Gulf describes for venting moisture?

5) I am dealing with a slightly mobile build--I worry about jacking up the slab to install the wheels--and any vibration to the slab by moving... I really don't want a chunk of this insulation to fall off like an egg shell!

6) The other upcoming event will be a curing fire--so far "done outdoors" unless I use the "propane fire ring" technique or "heat beads" with the garage doors open. Both techniques, however, require a final burn using wood to get the high temps. This would involve moving everything outdoors via forklift and possible-bumping, twisting, etc. forces---that a render might protect!

My structural slab is quite rigid--visibly at least, if the base is not supported equally, it will rock rather than flex.. But this pericrete seems very brittle!

Only someone who has worked with pericrete can answer these questions because they have actually observed the characteristics of a 10:1 mix as it is installed and as it ages!

I can see no reason for anyone to build up pericrete in 1" layers over a dome!
I saw on another website, someone advocating the use of lime with portland & vermiculite/perlite --only reason I can see would for it to adhere easier in thin coats...But this would also decrease the insulative properties?

Sorry for the "longwindedness" but a lot of questions requiring answers.
Also must evaluate risks vs advantages in the build!

1.Because perlcrete or vermicrete is made with portland cement it continues to increase in strength over time. One week is generally sufficient. A vermicrete mix contains about double the water needed for hydration so there is plenty of moisture there for this stage.

2. Only if you are making a ferrocement boat or high strength concrete would you require 28 days. the difference is minimal (look at a strength vs time graph of concrete strength)

3.No it will always be weak. But it only needs to be strong enough to stand up vertically and be firm enough to render over. The more cement you put into the mix the stronger it will be, but you drastically reduce its insulating value if you do.

4.There is some sense in this , but water left in this layer presents problems in removal. I take the view that it is better to dry the insuation layer completely, render over it ,then seal the render layer for a week using cling wrap.

5. If any falls off it's easy enough to patch it up.

6.The reason I advocate doing the vermicrete in 1" layers is so it has a better chance to dry. If you do it all in one layer it is much slower to dry the stuff that is buried deeper.