Structural Slab for new WFO

[mikku]

Re: Structural Slab for new WFO

This topic came up when I described mixing bag mix concrete with a plaster's drill and adding water in excess of bag instructions. I do not know the ratio of professionals to DIYers who use dry mix but it is a convenient product.

The point that I was making was you do not need a huge mixer to make concrete, but the drill I use is the price of a mixer. It is important to add your ingredients consistantly to maintain ratios between batches--regardless the batch size.

This forum is a mix of professionals and week-end DIYers. The topic of SP concrete should not be off limits because it takes accurate measurements to achieve proper results.

The minimum quantity for the BASF product is also 20 liters so you must justify its use before purchasing.

[Tscarborough]

Re: Structural Slab for new WFO

It is not offlimits, it is just counter productive. The professionals already know how to use SP, or at least when to use it, and the DIY guys (and girls) are not well served by even making it an option. When you are building a one-off personal project, the risk of failure is not worth the benefit, even though they may be considerable when it is used correctly in the correct application. Building a WFO does not have any area in which the risk or cost is worth the reward regarding the use of SP.

[Tscarborough]

Re: Structural Slab for new WFO

Mikku, if you want to talk about SP and related products, join this board and you will get all the discussion you want about construction beyond the scope of this forum:

Contractor Talk - Professional Construction & Remodeling Forum, News, Reviews, and Blogs | ContractorTalk

I am there as Tscarborough, same as all boards.

[david s]

Re: Structural Slab for new WFO

Unfortunately this is true. However the fact remains that adding additional water to a concrete mix in order to achieve the desired flow , leads to a weaker product. The additional water increases the volume resulting in looser bonding.All concrete that is delivered by truck contains superplasticisers.

Sorry, I was wrong. It is also only added by the concrete batchers on special order here too. Still doesn't alter the fact that its use will give you a superior product if you use it correctly.

[Tscarborough]

Re: Structural Slab for new WFO

Yes it will, key words being, "if you use it correctly". Again, for the construction of a WFO it is simply not needed, period.

[Tscarborough]

Re: Structural Slab for new WFO

When my Dad built this, we used an SP to facilitate pumping the concrete. It was in 1979-82 when commercial SP use was relatively new, and we dosed up to 100 trucks a day onsite. After dosing, each batch was tested and either sent on to the pumps or rejected. In the beginning, we lost 2 of 10, and even after thousands of trucks, we still lost one in 15.

https://maps.google.com/maps?hl=en&l...03449&t=h&z=18

[stonecutter]

Re: Structural Slab for new WFO

Mikku,

I am on the CT forum as well, and wrote a complete walk through about a hand pressed concrete project, in which polymers and admixes are discussed. You can get them in gallon sized jugs here ( sorry for the very offensive use of our imperial unit of measure) and they work well. And while I agree that a highly engineered concrete mix is pretty much over kill for most DIYers, there is a value to learning about it if counters or other pieces are being made.

[david s]

Re: Structural Slab for new WFO

Yes it will, key words being, "if you use it correctly". Again, for the construction of a WFO it is simply not needed, period.

The topic arose about the mixing of concrete for a project that did not involve an oven. The strength of a supporting slab for a WFO is a crucial factor because of the extreme weight involved, also as the stand design often requires a fairly wide span. Adequate strength can be provided by a combination of concrete strength, reinforcement and its placement as well as thickness. In my case I need a light thin slab so rely on reinforcement and concrete strength to reduce thickness.
The Imperial Neanderthal comment was meant as a friendly jibe.

[Tscarborough]

Re: Structural Slab for new WFO

I would say that 100% of all slabs and stands built on this site are around 3-400% overbuilt for their use, not even counting using SP.

[david s]

Re: Structural Slab for new WFO

Yes you are right. A 4" slab, properly vibrated with adequate and well placed reinforcement will be quite adequate. I was not advocating the use of SP in the design.

[mikku]

Re: Structural Slab for new WFO

Tscarborough -/ Stonecutter-

Thanks, I will check out the forum and join when I have time. Just put in a 17 hour day and having a little refreshment.

2) I'm asking about SP concrete because I want to use it for my own application and I want to do it right--if it doesn't come out right the first time, I'll do it until it does!

3) My stand is 1000% overkill--so what! It is a hobby--next time I'll lighten it up a little.

4) I like what I see from BASF- no vibration concrete.

5) Tscarborough--your comment "The professionals already know how to use SP, or at least when to use it, and the DIY guys (and girls) are not well served by making it an option."

"On a lighter note"- you can substitute SP with "condom" or countless other things. I'd rather determine what is important to me by access to information--than to have it decided by someone else -- like an 1984 society.

Please take no offense-- I really like the response generated by this topic and personal opinions given!

[mikku]

Re: Structural Slab for new WFO

Back to my oven operation.
This is maybe the 7th time to fire the WFO.
Still sitting on a temporary base--like Brickies observation--too low like all Japanese furniture!

I started the oven at 8:30 this morning with some kindling and three pieces of dry oak. I start the oven with the wood about flush with the intersection of the dome and entrance. This is a smoky place to burn--the flames wash over the oven opening and are drawn up the chimney--but excess smoke rolls out the front.

Once that the fire establishes itself, I take a stick and push the entire fire to the rear of the oven--at that point the flames lick across the top of the dome and swirl around --what exits the oven is only heat--and very little visable smoke.

Once that the fire was pushed to the center rear, I added two more sticks of oak.

At 9:30, there was a glowing bed of coals and remnants of the oak spread over the floor of the oven. I took an IR temperature reading and it registered 575 deg C rear wall about 8" up.

On previous days of burning, I would have added another 3 or 4 pieces of oak and let it really burn clean for another hour or so. But on other days, the temperature maxed my IR thermometer and the oven was unusable until the temp dropped into baking ranges. Today, instead of firing another time--I removed the coals and asked my wife to put the oven door in place at 11:30--hoping that it would be enough time to cool so that my door would not spontaneously combust.

I had work to do today--like a job. So I returned to the house at 13:30--and placed my little bimetal thermometer into the oven and closed the door again. After about 10 minutes, all that the oven read was about 350 deg F. Normal temperature for bread making in a standard gas oven.

My wife had mixed dough for Rye bread and had punched it down just minutes before I return home.. I told her that she could bake once the bread rose again but she wanted to wait until I returned...

Work lasted longer than I expected and my wife decided to bake the bread in our normal Magic Chef--She was upset that I was gone all day--leaving the WFO unattended, and did not want to screw around with her trying to learn how to bake in a WFO...

Cannot win for loosing!
At least there is fresh bread--but an angry wife retired for the evening--tired of waiting for me again!

Oven heats very quickly--but I need to determine when it is saturated. Those with thermal couples would know easily by looking at their read outs. I'll have to learn by watching and measuring how long it takes to heat--then see how long it will stay hot...

Only thing accomplished with the WFO was to find out that even though the oven heats quickly--doesn't mean that the mass is heated sufficiently to bake bread --6 hours after removing the coals???

[mikku]

Re: Structural Slab for new WFO

Gee how time flies when your having fun!

My WFO still sits where I moved it a couple of months ago, no stand under a heavy duty tarp that keeps things dry.

If there is time, I fire it up on Sundays to keep it dried out.

It is the rainy season here so the weather is unpredictable--nearing August, the skies should clear and the really HOT of summer should be felt.

Still the evenings are cool enough to sleep without air conditioning because of the way the wind directions change in the late afternoon.

Almost every day between 5 and 6, whatever stagnant air has accumulated around here gets pushed out by the cool air falling from the nearby mountains- Nantai-san, Shirani-san, and another with a name I keep forgetting...Actually the mountains (called the Minami Alps) begin here and traverse the length of Japan--with mountains almost continuous to the Japan sea side of the island. Really a lot of rugged terrain and interesting roads to travel--when there is time to get out to adventure.

I am beginning to learn a few things about using a WFO--I guess it all takes time, each oven is a little different...so no one can really give exact advice on how to fire one over the other.

Sunday, I did not start a fire until early afternoon 1530 or later...after it began burning nicely...I loaded it completely with dry oak firewood and let it roar. Really not too much roaring but the fire quickly heated the oven to what I believe a saturated temperature. I quit putting wood into the oven around 1800 and removed the coals at 2000. Instead of using a "blow tube" that you physically blow into, I took a 5' section of 3/8" flexible copper tubing , one end flared and used the "blow gun" and compressor to blast air into the oven!

It makes a pretty good cloud of ash dust, but it does clean the oven nicely. I just stay out of the line of the hot ashes and left over charcoal pieces that fly around!

Since I do not own any peels yet, I put a pizza--maybe 12" diameter on a pizza pan into the oven. I noticed that the crust started moving around as soon as the pan hit the bricks. After checking several times (the bottom of the crust) for browning- I removed the pizza in a little over 3 minutes. Everything looked fine and the crust was not burnt in anyway! Just a nice crust.

While removing the pizza, it started to sprinkle and rain developed quickly! I had already removed the SS chimney when I blew the ashes out--so all that was needed was to put something over the chimney hole--a couple of firebrick that were handy and then pull the tarp over to keep water away! I really hope I can find time to make an enclosure and base for this oven. Like Brickie was saying before--to paraphrase his comment--just another Japanese thing that you had to kneel down to use! The kneeling down is beginning to be a pain in the butt!

Oven holds heat pretty well, morning after temperature still over 260degC, roasted a block of beef in the morning--evening temperature still over 200deg C.
Ended up baking a few loafs of bread the following day!

I'll see if there is some pictures to attach..
Nice to use the oven--even though it is not done!









The oven really fires up quickly, the entire casting shows no signs of cracking. It is a 2 piece dome, with separate transition to landing and chimney. I don't know all the fuss about brick cracking???? The pericrete has cracked and so has the render (first coat).

funny thing today, I found a shop that I can buy any length pieces of ceramic fiber. This is a woodstove shop that carries it all the time. I bought a piece .5m x1m today 25mm thick, that I will put two layers thick into my stainless oven door.

Maybe I should show the door in progress?

[mikku]

Re: Structural Slab for new WFO

Door in progress-





Same time I got wood stove woven rope (door seal) and furnace cement to attach to rope to the door surround. That should seal things up nicely! Have to wait a few days to put the time into finishing the door!

[mikku]

Re: Structural Slab for new WFO

Today is the last day for "Obon Yasumi" or Summer vacation for most of the people in Japan. This week-end was the second time that I have had a bunch of people over for pizza and things. Probably 20 people last night and most of them at one time put on latex gloves and got into the act of stretching dough and preparing pizza. It sure makes a big difference when you can change from being the lone ranger making all the pizzas to the host that makes the gathering possible.

The day before, my wife and I were guided though the steps of making sourdough bread by Lawrence Sensei. It is sure nice to have his expertise available as we ventured into new territory of bread making. For those of you who have not tried it before--a bit of warning. "It takes a very long time to do this type of recipe" If you don't have the time or patience--don't even attempt it...

The results were fantastic. My guests last night polished off everything that was made plus a couple loaves of potato bread and blueberry cake. Also grilled some steak --after that pork ribs, then back to pizza for the end of the evening.

I ended up just putting the door in place when I decided to quit for the evening. the small holes left for attaching the handles must have leaked enough oxygen into the oven because there were still active coals present this morning and the temperature was at 310degC.

Wife decided to make cookies and banana loaf but the oven cools so slowly now that it was after 5PM before she could get cookie baking temperatures. She is finally getting the hang of things--using the oven when I am off at work.

Out of the 10 days most people take for summer vacation, I ended up with one actual day off. The rest of the time been busy with scheduling work and making new contacts. Seems like the economy is turning around a bit this year.