Vermiculite concrete insulating base questions??

[slowfood]

I am mounting my oven onto a trailer, I am about to cast the concrete slab (2") and then the Vermiculite concrete insulation slab. My question is this, How strong is Vermiculate concrete (Movement etc) And will the concrete be spongy? It has to be firm and strong to take the oven and keep the segmented floor level and in place, Thank you

[twobecks]

Hi slowfood,

I laid my firebricks (230 x 114 x 25mm) directly onto the vermiculite-concrete layer, and then installed my modular oven straight on top of that.

There were no issues strength-wise. I was really worried about the vermiculite-concrete compressing and making the firebrick floor uneven, but these fears were unfounded. Whilst fitting the cast pieces of the dome into position, the firebricks were being trod on by blokes weighing in at 100kg+ (as well as the dome itself) with no ill effects.

The only thing I have found is that the mix can be "chipped away" from the side unless it is shuttered in or retained.

With regards to putting this on a trailer, I can't comment on what this would mean if the trailer went over a bump - if the mass of the oven above would shock the vermicrete into compressing.

Good luck with the build!

Steve

[turkey]

I do not believe it will compress easily,but if worried you could buy a couple of dedicated insulation firebricks and place them in areas of expected weight to help out the vermicrete?

I would expect it to be mechanically strong to compression but as said brittle and susceptible to chipping, aim to keep it sealed somehow. Also perhaps skim over it where items will be stuck down to maximise this, you don't want the bond between base and oven to break and the oven to leave the floor over a bump.

perhaps even some structural ties, these might lower the insulation or act as small heat sinks but could offer more peace of mind?

[slowfood]

How thicjk was your vermiculite slab?

I was thinking of using concrete grassblock filled with insulation (Varmiculite/Perlite), I think this would work well.

How can I post a picture with this post?

[twobecks]

My vermicrete slab is just 1.5", but this sits on top of foil wrapped calcium silicate board. As the KL kit just recommends the CS board, I thought I'd beef up the insulation a bit more.

The slab area is bigger than the board underneath and completely encloses it.

No strength issues, other than being a little crumbly at the edges.

You can select pictures from the attachment area when you post a reply.

[tonyb]

Slowfood, I think you need to think about the purpose of insulation on a trailer based oven, in particular how you intend using the wfo and what baking/cooked products you intend. Depending on the answers to this you might not need much insulation at all, other than to protect the trailer and curious people touching the wfo.

[slowfood]

Well basically I have set out to build the best oven I can observing all the information I can find on the net. And it seems Insulation is very important as my cast is at least 3 inches thick I know the oven will take hours to reach maximum heat, So in order to make the most of it and also save on fuel etc I intend to insulate it to the max, On my first oven I damaged the supporting slab because I had little insulation under the hearth (The Re-Bar expanded and blew the inderside of the slab)

The reason I am going to this extreme is because it's going to be "bionic" Like Steve Austin.... I think I'll follow the yanks and go for the full 4" of insulating concrete (I can't justify the cs board) Thanks.

[tonyb]

The reason why I commented on the question of insulation was that if you are just doing day events only doing pizza, you would probably be better off with a thinner oven with minimum insulation. Whereas if you were doing multi day events, some early morning bread would probably do a roaring trade, and a heavier and well insulated wfo would be better. I can almost smell the freshly baked bread aroma wafting over the campsite

[cannyfradock]

Slowfood

....uploading images... ukwoodfiredovenforum.proboards.com/index.cgi?board=info&action=display&thread=111

I'd be very tempted to keep the weight down to a bare minimum. Your 3" thick modular oven probably weighs a far bit so you are probably limited to how much more weight you can add to make it feasable to be mounted on a braked trailer, which can be pulled by a normal vehicle.

Taking the idea of it being used for fairs etc...this would be my approach.....

On your flatbed trailer I would lay ex-met. On top of this lat a cal-cil board....then a layer of celcon bricks (3") laid flat ...then 1" fire-bricks. Lay your oven on top of this and use the thin pliable joist straps to secure it to your trailer.....Forget the insulating blanket, cover the dome with chicken wire, but just use 3" of vermecrete. Another layer of chicken wire and lay 2 coats of K-rend (with chicken wire in between the coats. The vermecrete will be your insulation, but also act as a fire-stop to protect the k-rend.

I am not knocking your suggestion......I'm just concerned about the weight...... The above comment is only a suggestion of how I would go about such a project.....it's only my thoughts!!!

Cheapest place for 1" fire-bricks and cal-cil board is Liam at www.kilnlinings.co.uk/ .....any other building materials can be bought at Jewsons with our members discount... woodovenukforum.forumup.co.uk/viewtopic.php?t=678&mforum=woodovenukforum

You may have found cheaper sources....these are just options...

All the best with your project.

Terry

nb 1......The laws are changing soon on trailers/braked trailers.

nb 2.... I have recently added this new category to the forum.. ukwoodfiredovenforum.proboards.com/index.cgi?board=membersbuyandsell

[slowfood]

Thanks Terry but everything is done now, I have 80mm of Vermiculite sitting on 60mm string concrete, Today I installed the Oven, the suspension is holding up no problem, (The trailer is a Tandem with very large wheels) I asked a couple of trailer peeps to check out my plan and it got thumbs up. However next time I shall try to save weight, The problem all along was my refractory suplier reccomended casting refactory no thinner than 100mm so I always guessed I was pushing my luck with the 75-80mm I have, As it was allways going to be moblie I needed to make sure the oven was strong. I'll post some photo's in the mobile oven section. I found castreekilnpottery to be the cheapest for ceramic blanket at £5 per metre (25mm x 610) (Kilnlinings are £8 per metre for the same). Thanks, when it's completed I'll give it a good towing session to see how it performes. Thanks