Morter issues

[Michelleski]

Just started my WFO, spent 2 days getting to this point (just the brick laying part) and have no finger tips left!!! My major issue is the mortar I'm using 3:1:1:1 mix but it keeps setting in the barrow so I have to keep adding water to make it usable!! Doesn't seem right any ideas would be greatly appreciated. Would also like opinion on outer arch, it finishes with a full brick so there is no keystone will this affect the strength of the arch??
Love this community I've learnt so much!!

[UtahBeehiver]

Make smaller batches of home brew. I used a gallon bucket. How did you insulate the floor. I can't tell from the pic but it appears the floor and dome walls sit on the concrete hearth which will heat sink temp away into the hearth. The inverted v is starting to show up in the inside dome joints so a bevel will be required to reduce v. Hemi-archs are self supporting.

[Michelleski]

Hi thanks for that, I have started mixing smaller batches, thought there might be a better recipe that helps with this issue.
The hearth is calcium ciliate board on the concrete slab with large 250mm thick fire brick tile on top. I've placed first course soldier style butting up against the floor and mortared into place. Hope that's ok?
I hadn't heard anyone talk about the inverted "v" but I see what you mean, and I'll watch out for that.

[Gretsch]

Mortar on the hands is a killer. I use nitrile gloves under another set of heavier duty gloves it keeps the alkaline off the skin and your hands will be nice and soft for the missus that night.

[david s]

Hi thanks for that, I have started mixing smaller batches, thought there might be a better recipe that helps with this issue.
The hearth is calcium ciliate board on the concrete slab with large 250mm thick fire brick tile on top. I've placed first course soldier style butting up against the floor and mortared into place. Hope that's ok?
I hadn't heard anyone talk about the inverted "v" but I see what you mean, and I'll watch out for that.

If using calsil underfloor insulation the usual thickness is 50 mm. Likewise dense firebrick floor is usually 50 mm. If yours is 250mm thick, it will take a very long time to reach pizza cooking temp, (maybe/hopefully you meant 25 mm) The larger and thinner the floor tiles, the greater the tendency to crack. That’s why many ovens use loosely laid smaller brick units.

[david s]

Just started my WFO, spent 2 days getting to this point (just the brick laying part) and have no finger tips left!!! My major issue is the mortar I'm using 3:1:1:1 mix but it keeps setting in the barrow so I have to keep adding water to make it usable!! Doesn't seem right any ideas would be greatly appreciated. Would also like opinion on outer arch, it finishes with a full brick so there is no keystone will this affect the strength of the arch??
Love this community I've learnt so much!!

The addition of lime to the homebrew actually increases the working time. If you have to add water more than once then it should be discarded. In hot weather keep the mortar out of the sun and use chilled water when mixing. A steel barrow will also quickly conduct heat into the mortar mix so start with a cool barrow and keep it shaded.If you have a batch that’s going off use it to fill those bigger gaps on the outside of the dome.

[Michelleski]

Hi David, whoops yeah the underfloor is 50mm and the fire brick is 50mm! I've been mixing the motor in steel barrow and it's been quite hot here (around 30 degree celcius ), I'll try all the tips
- small batches
- cool water if hot day
- different container to mix it in
- and not use if I have to add water more than once.

thanks for all the tips

[UtahBeehiver]

If you do a search on inverted v you will see several posts. But here is an example of one. The higher you go the more pronounce the v becomes. You do not need to bevel the whole length of the brick just near the front edge on the inside of the dome. This can be done with a saw or angle grinder with a diamond blade or cup.

PS this builder place the bricks upside down making the inverted v more pronounced.

[david s]

Hi David, whoops yeah the underfloor is 50mm and the fire brick is 50mm! I've been mixing the motor in steel barrow and it's been quite hot here (around 30 degree celcius ), I'll try all the tips
- small batches
- cool water if hot day
- different container to mix it in
- and not use if I have to add water more than once.

thanks for all the tips

Just had another thought. I was presuming you are using standard cement in the homebrew mix. If however you are using calcium aluminate cement it has a far shorter working time. The addition of lime actually accelerates the already faster reaction causing even less working time. I believe there is a recipe in the Pompeii plans that suggests a mix of these two ingredients. In practice the stuff will harden so fast you won’t be able to get to the end of a small batch before it’s unusable. The homebrew mix only works with standard calcium silicate (Portland ) cement.

[Gretsch]

The homebrew mix only works with standard calcium silicate (Portland ) cement.

Portland cement is Calcium Silicate ?

[cobblerdave]

Gday
Get yourselves of to "bunnies."
Park yourself proudly in the" tradies" section.
Firsr ask for cement. No you don't want builders cement or the Chinese stuff that's been on a boat for forever and or can contain furnuse cinter. It's the first glue for your mix
Next builders sand, keep out of the gardening section No play box sand, it's fine but not enough toughness between the grains no grip. It's the matrix that the other bits stick to.
Clay, fireclay sounds greatest, but it's not needed. Your not melting metal the goals for the "workability" of you mortar the ability to stick and hold on 2 surfaces at the same time is what your after. Look for "brickies clay"
Lime, again keep out of the garden section. It's not Ag lime it's brickies lime.After the "Portland cement" loses it strength after 300c this will be you long term "glue" or cementance matersial.
Sand and clay. Is available at a bulk supplies, it might be called brickies sand, brickies loam. You can then not worry about the sand/clay but. Depending where you are in Aust, and how the housing is built.
hopes this helps
dave

[david s]

Hi Dave,
unfortunately the only cement you can buy from Bunnings now is the cheap Vietnamese stuff (Bastion). They no longer stock Cement Australia products. I am so pissed off with their policy that whenever possible I buy my cement (Cement Australia) from a small local hardware shop. I’ve also sold my Westfarmers shares who are the owners of Bunnings. You obviously haven’t bought cement from them for a while as this happened about two years ago.
Cheers,
Dave

[Gretsch]

While on this subject, I've got a good bucket or more of firebrick dust from my cuttings, just seems a shame to throw it out.
Can it be used in a batch of mortar ?
If not in between the bricks, in the render mix ?

[wotavidone]

My company's refractory manual defines fireclays as clay deposits that have been calcined, crushed and sized.
So If you have a bucket of brick dust from cutting fire brick, you have a valuable commodity.
Was it cut wet or dry?

[Gretsch]

It was cut wet so most of it is very fine powder and then there's brick chips through it as well.
Hey maybe I can trade it for a bitcoin