Found this refractory cement recipe, any comments?

[SentencedToBurn]

Hi guys

I'm only a couple of weeks away from finally making a start on the actual build of my oven (2 weeks off over Xmas so that's all me and the kids are doing).

I came across this recipe here and had a couple of questions: www.traditionaloven.com/tutorials/concrete.html

The actual ingridients listed are:
-3 shovels of the gravel or grog/crushed firebricks

-2 shovels of sand (Portland concrete type only)

-2 shovels of the cement

-1/2 shovel of lime (for Portland concrete type)

-Approximately 6-7 liters of water to mix the concrete.

Questions:

• This recipe above is a bit different to Downunderdave's recipe - will this work ok? The only reason I ask is that I found powdered clay locally but it's a bit of a ripoff.
• The recipe above includes gravel - I have about a quarter cube of fine riverstones (smooth ones, size roughly 1/4" to 1" in size) - would this work instead? Just I already have them as a leftover from another project.

Any help would be greatly appreciated, maybe refractory cement recipes that don't include powdered clay.. Thanks!

[downunderdave]

Dec 15, 2016 19:40:06 GMT SentencedToBurn said:

Hi guys

I'm only a couple of weeks away from finally making a start on the actual build of my oven (2 weeks off over Xmas so that's all me and the kids are doing).

I came across this recipe here and had a couple of questions: www.traditionaloven.com/tutorials/concrete.html

The actual ingridients listed are:
-3 shovels of the gravel or grog/crushed firebricks

-2 shovels of sand (Portland concrete type only)

-2 shovels of the cement

-1/2 shovel of lime (for Portland concrete type)

-Approximately 6-7 liters of water to mix the concrete.

Questions:

• This recipe above is a bit different to Downunderdave's recipe - will this work ok? The only reason I ask is that I found
  
  powdered clay locally but it's a bit of a ripoff.
• The recipe above includes gravel - I have about a quarter cube of fine riverstones (smooth ones, size roughly 1/4" to 1" in size) - would this work instead? Just I already have them as a leftover from another project.

Any help would be greatly appreciated, maybe refractory cement recipes that don't include powdered clay.. Thanks!

Are you planning to use this mix as a castable or as a
mortar? If using it as a castable the addition of a small proportion of powdered clay improves the workability of the mix by imparting some stickiness, but too much will increase shrinkage. If it's use is for mortar there should be no coarse aggregate in the mix, only sand or finer grog.

[SentencedToBurn]

Awesome thanks Dave. It's only used as a mortar.

Will skip the stones then.