Hydraulic lime at High-Temperature Mortar?

New to group, I’m from Portugal !!!
I preparing to build a Fired Masonry Cookstove, at this moment I’m planning the needed materials and I trying to find out which mortar shal I use.
I was digging through internet about suitable mortar, and to be honest I’m quite confused.
Some places saying to use only fire clay and silica sand with a small amount of fly ash, other places send us to the refractory mortar, then I found out the high-temperature mortar recipe and sounds me great.
I need your support to clarify two doubts from my side:

  • Can I use Hydraulic lime instead of Hydrated Lime ( here in Portugal I do not know where can I found out the Hydrated Lime)?
  • The High -temperature can I use it to glue the refractory bricks, or only the walls of the stove?

Sorry for my English!
Nuno Iglésias

Hello Nuno, and welcome to the BrickWood forum!

Hydraulic lime is a different product from hydrated lime. One thing is that hydraulic lime cures (sets) much faster, so your working time is much shorter.

I am not sure of your building plan. In a BrickWood oven, you would use refractory bricks anywhere the fire touches, and you would use the high-temperature mortar everywhere EXCEPT the floor. For the refractory bricks in the floor (or hearth), you do not use any mortar at all. They are pushed together and held in place by the brick frame that surrounds them.

@BrickWood may have more wisdom to share about hydraulic lime.

I hope this is helpful to you, and please feel free to ask more questions!

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Thank you @bikerbudmatt for your prompt anwser. I will take one of the Walker Stove a a guidance. I will use ordinary red bricks to build the stove walls, the core I will use refractory bricks, and as we in Portugal do not need so much the enviroment heating, I will use too refractory bricks to isolate all places from where the hot air passes.
So my question, can I use the high-temperature mortar recipe driscribed here, to line the red bricks walls of the stove, bonde the refractory bricks from the core and, paste into the red bricks the 30mm refractory plates?
So, is this recipe that I can use in all mounting stove?

Thank you,

Hello, Nuno!

I’ve asked for assistance on this. I want to make sure my answer on this is responsible, so that we have some confidence your oven will hold together under heat.

Hello @bikerbudmatt,
The idea is to put some bricks like a Pilar to hold The oven, or use some square iron!

The lime in the High-Temp recipe is added to make the mortar a bit more “fluffy” and easier to work with. Some contractors will leave the lime out all together, but I wouldn’t recommend that if you are just starting out.

The lime really does make a difference (but don’t add any more than recommend). Additionally, it prolongs the curing process of the mortar so you will have more time during the mortar application period. This can come in handy if this is your 1st, 2nd or even 10th oven build.

As @bikerbudmatt mentioned - you only need to put high-temp mortar where fire touches brick. So if a brick is exposed to flame - you will use HT mortar (but not on the hearth brick).

No matter what type of oven you build - MAKE SURE YOU PROPERLY INSULATE THE OVEN with 2 or 3 layers of ceramic fiber blanket!

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Thank you very much for your support and advises. I will follow stricly the formula for the HT mortar described here in the forum, and I will use this mortar for all the assembly.