Pdx 42" update

[MarkJerling]

I'd be interested to see some research. I've not seen any literature as to disadvantages of wet curing concrete.

See for instance: Microsoft Word - Articles1. English.doc (irbnet.de)

And: Role of Concrete Curing (cement.org)

And: Curing Concrete, Chapter 12 (memphis.edu)

As I work in the construction field, I'd be most interested to learn of studies showing the opposite result.

[NCMan]

Contrary to common myth, spraying a cement product down w/water to keep it wet is not good for it, despite what some may have read or believe. It actually weakens the outer surface of the product and can cause spalling, etc. The best method is to retain the existing moisture, slow down the drying process and not add any additional water to it. It's tough to compete w/all the internet myths out there (there are so many), so people believe it. It's just not true. Having said that, as Gulf said, it'll be ok in the end. Not pretty, but it will probably be structurally sound enough to build on.

[Macrinehart]

So we hit a low of 32 last night but with the space heater going and build covered it was very comfortable warm when I check this AM. I fixed up my tenting rush job from last night and gave the hearth slab a drink with the sprinkler set on shower.

It does look a little rough. But, the hearth slab does not have to be a "burnt finish". It just needs to be level.

There is an ever so slight slope to the front. I notice that water pools up on the slab but over a few minutes it gradually drains off the front. This is not unexpected. When I checked my level the last time the bubble was between the lines but touching one side indicating this slope. I decided further tweeking of the stand wasn't necessary.

Yesterday I tried to put a bull nose edge on after taking that picture, but mostly just made a mess that I'm sure will have to touch up when the forms come off.

[Macrinehart]

Even if the top is a little sandy that's not to say it won't be strong enough. After about 2 days, spray it down with a hose and quite high pressure. If the water does not dig holes, it will be fine.

I suppose time will tell. So now that I've cleaned up and got a glass of wine, the narrative version of today. Up at 6:40 AM - thank you cats - I cooked up the elk breakfast sausage, downed four patties with coffee and toast and hit the road to home depot for tool rental and concrete. (Every big workday should start with a hearty breakfast!)

Rented a concrete mixer, float, and the truck, and baught 25 bags of concrete plus flow guard. Asked for help loading the concrete and then proceeded to Complete the full load without help, 1500 lbs, round 1.

At home preping the job site included sifting 25 bag of concrete to the back yard...this time I used a cart, but thats still counts for two sets of 25 reps with 60 lbs bags. Getting a good workout! Then there was some running around for missing supplies and after my guilty pleasure of the 2 cheeseburger meal with a coke at McDs, I was ready to start mixing at Noon.

So I read that safety thread, and for gear I had a pair of rubberized, full arm chemical gloves (they were cheap, so why not?) Face shield and respirator. I was not interested in breathing concrete dust today. But after 10 bags I could barely see through the face shield so that came off.

It took a bit to get my rhythm, but once I got going the sun came out, it got up to about 55F, and it was a good day for back breaking outdoor labor. I got another rep of lifting the 60 lb bags into the concrete mixer, and then there were another set of lifting the 5 gallon bucket of concrete up to stand, those were squats, and considerably heavier than 60 lbs!

So four hours in, I still have a functional back and got a solid workout. About half way through I was not liking the texture of the poured concrete. But what can you do? I just decided to try and keep working it so it didn't set up too much.

Thanks for the tip Mark! I setup a tent over the concrete with some stakes, plumb line and a tarp. Then I cleaned our the space under the stand and setup a space heater there. The whole thing is covered by my canopy and some tarp walls. Hopefully that's enough to keep it above freezing. Supposed to be getting down close the freezing at night for the next couple of days. We'll see.

[Gulf]

It does look a little rough. But, the hearth slab does not have to be a "burnt finish". It just needs to be level.

[MarkJerling]

Looks good. Once it's set, keep it wet for a few days by spraying it down, but don't let it freeze. Even if the top is a little sandy that's not to say it won't be strong enough. After about 2 days, spray it down with a hose and quite high pressure. If the water does not dig holes, it will be fine. The water should blow off any loose sandy material.

[Macrinehart]

It's a beautiful day, and I was impatient so I did the hearth by myself. I finished in about 4 hours, hopefully I didn't mess it up. Little concerned to be honest, the hearth set up a lot faster than the pad, so I felt like it was a bit of a race to get all the concrete in while I could still work it.

The top seems a little sandy, this doesn't feel right at the gut level but maybe it's OK? You guys tell me if I just made a big mess.... Here are some pics.

[Macrinehart]

Ready to pour the hearth! Unfortunately I'm a day behind so I may have to wait a week for Jesus, Constantino and Machete to be ready.

I setup my fullsize template and it looks good. The front of the oven opening lines up with the front of the yardstick in the image below.

[Macrinehart]

Almost there! Today I made quite a bit of progress on the form with most trim pieces cut to size, the rebar laid out and zip-tied. The weather is still not great, several days of freezing and thawing plus rain today is causing a lot of ground movement, which in turn resulted in most of my form legs getting loose and collapsing.

Another issue, rebar is too high. Will be cutting supports down to 1".

The concrete crew came by to check out progress and liked what the saw. Will have to wait a week for better weather before pouring. Tomorrow I hope to finish trim, weep holes and final prep before pouring concrete.

[fhausback]

I’m adding thermocouples to mine for the geek factor. When I was building bbq smokers I used that info all the time. Once I learned how to run a particular smoker, I used the probes less and less.

Knowing that, I’m not too concerned about long term durability, but will make sure a couple of them are easily replaceable. As others have said, knowing when the bricks are saturated would be handy.

[Chach]

I used to use my IR gun now I just look at it and barely use it for the oven. I would have liked to see what the outer brick temp is as well so I agree with JR out of curiousity, but I don’t see it a necessity. If you want to geek out over your oven now is the time.

Ricky

[JRPizza]

I didn't use thermocouples, and other than the geek factor (I"m also a graph and data guy) probably would not use them when firing for both a short and long term cook. I do however wish I had a way to see what the outside brick temperature was when we are doing a same day cook with retained heat. As soon as the soot burns off the inside of the dome the IR gun says the dome is in the 800's (for example) but the IR gun will never tell you when the bricks are saturated. I have in the past closed the oven off too soon only to have the temp rapidly drop to the low 300's, which would not happen if I could see that the heat had not transferred through the thickness of the bricks. This could also likely be accomplished with a probe thermometer poked through the shell touching the brick, which would probably be lower maintenance and more durable. I have gotten better at timing when the oven has got enough heat into it to hold a good cooking temperature, but some data would be nice to have.

[Gulf]

.......should the insulation go under the wall and floor? I think yes, but for some reason I have seen a clear example that illustrates this step.......

I agree with Giovanni Rossi, at least by by 2" imo. If you do 3" of 1" ceramic fiber blanket over the dome, a 3rd layer could overlap and extend down to the the tiles.

....I think I might be in over $800 on Calsil board. Does that seem about right?...

Absolutely Not! There are sources for CalSil that are hundreds of dollars cheaper for an oven this size.

[Giovanni Rossi]

I think the main issue was durability. Again going from memory, I believe "K" type thermocouples is what should be used. Those more knowledgeable will probably chime in.

I haven't priced Ca Silicate alone as I'm working with a kit, but I understand it's a big part of the cost of a DIY oven.
I'm planning a layer of Foamglas under the CaSil. Also expensive and tough to source.

The insulation board goes under both floor and dome wall. Ideally it should extend beyond that as some would argue not to have all of the weight of the dome right on the edge of the CaSil board.

[Macrinehart]

Thank you Giovanni. I have read up on both thermocouples and the IR thermometers and find myself more in the camp of those that like to geek out on instru.ents and charting things. It's actually how I make a living in my day job. the idea of having temperature plots from multiple points is very enticing!

I also have excess PVC, so that's handy!

One other question, should the insulation go under the wall and floor? I think yes, but for some reason I have seen a clear example that illustrates this step.

I am planning on calcium silicate board, which is very pricy but the climate here is wet so I want something that can handle a little moisture without breaking down or loosing it's insulating properties. Just want to purchase the correct quantity. I think I might be in over $800 on Calsil board. Does that seem about right?

Also plan on using the mosaic tiles to elevate the insulation layer.