Another UK oven project

[nissanneill]

Re: Another UK oven project

Hi Matt,
that is a very quick reply!
When you mix your concrete, we should always start with sufficient water in the mixer for most of the batch being made in that mix. I usually mix to and beyond the mixer's capability which sets a few other challenges there. I had a 3.5 cubic foot mixer when building the house and now have a 2.5 cubic foot mixer which get a thorough workout occassionally. I like to 'fill' a large builders wheelbarrow with each mix.
Next add the portland cement as this is the 'glue' part of the mix. Add your 'aggregate' which I would call the crushed gravel or rock. This is simply the bulking agent and its surface should be thouroughly coated with the wet cement mix. Then add your sand which fills in all the gaps between the aggregate. Add a little water to achieve the required 'slump'. This will make your maximum strength concrete so long as you stick to the makers formula for the concrete's final use.
I still feel that a 6" slab with a couple of rebars in the perimeter is still a bit light on especially when you are going to be putting over a ton of bricks and concrete which is sitting on reactive clay.

Neill

[aureole]

Re: Another UK oven project

The foundation was 6" all around. Not shown in the photos was a bulk bag (~tonne) of crushed rock foundation compacted underneath the form. We went down about 3" into the clay bed. I was told that when you get down here, the clay bed is essentially permanently wet (more or less), hence why you bother.

The concrete was made as follows:

Water (~1/2 bucket)
Add little aggregate (1 shovel)
Add all mortar slowly (1 bucket), mix
Add rest of the aggregate (6 buckets)
Add water to consistency

[nissanneill]

Re: Another UK oven project

Hi aureole,
I hope not to scare you but I am a little concerned over your foundation!
Firstly, I would have dug a beam footing, say 18" deep x 12" wide on the perimeter with 2 or 3 1/2" rebars top and bottom and incorprratinf the 4" reinforced slab on top. I know that digging through clay is hard, especially if it is dry, but also very sticky if wet.
I have dug almost 100 metres around my home for retaining walls so can speak from experience. I even used a pneumatic jack hammer for some foundations.
I say this especially if you are pouring this on a clay base which, if it gets wet and absorbs the moisture, will move. Also the perimeter will be carrying the total weight directly over the cement blocks presumably used for the base construction.
This can be helped by filling the blocks with concrete and some reinforcing bar as you build the layers. Almost like building solid concrete (reinforced) sides.
Also, what was the ratio of gravel (crushed rock), sand and cement?
It looks from your photos, that you mixed it by a mixer. How and in what order did you mix the concrete? I ask this as a much stronger mix is achieved by mixing in a certain way to other even when using the same ingredient ratios.

Neill

[aureole]

Well, this week was the big day: started working on the oven by laying the foundations.

I'm a complete beginner to this all, so I'm quite nervous about pretty much everything, as well as being a bit inexperienced. Luckily, I've got a bunch of friends that do know what they're doing!

Digging out was hard work since it's on an aggravating angle. I was advised to keep going 'till I hit the clay: I wasn't sure when this'd be, but when I hit it - yup, I knew about it, that stuff is pretty bloody solid.

Not sure about curing my base - how long it will be before I can add the blocks on top. Also, I'm not able to be at home wetting it all the time - I left it uncovered last night (finished pour at 5pm), covered it this morning and pooled on top, but I'm worried it'll dry (or has dried already!) too much! Any advice?

Pizza oven pictures - WIP!

Pizza oven costs (so far!)