old style lime mix instead of refractofy cement

[andy71180]

hi guys! has any one used the one part portland cement one part hydrated lime six part sand mix instead of fire resistant cement which can be costly.
please tell me if you have used it pros,cons!


cheers

[Tscarborough]

That is a regular Type N mortar, with minimal refractory characteristics. That said, I have seen a lot of old fireplaces that were in heavy use and good shape that used it with 3/8" joints.

For the effort required to build an oven, I would not risk it, though.

[dmun]

If you're out to save money, I'd stick with the tried and true homebrew mortar. (High Heat Mortar Primer)

Here is the recipe for fire clay mortar, where you measure by volume (use a bucket or shovel to measure):

1 part portland
3 parts sand
1 part lime
1 part fire clay

I know fireclay is a little hard to find in the UK, but it's worth the search. It's the only really refractory item in the mix. If mason's suppliers don't have it try pottery supplies. I haven't used the homebrew stuff, but it's said to work better if you get really fine sand.

[stonejohn]

HI D,

I'am a little surprised to see the lime in the mix, I thought that it would burn out. I have been mixing a fireclay mortar at
2 parts sand
1 part port
1 part fireclay
I would have to admit that the lime would make it easier to lay, If it had no ill effects. I learned from an old time brick mason, but that does'nt mean it was correct. any thoughts on this?

[david s]

The lime will not deteriorate with heat like the portland cement does over 300C. Use the 3:1:1:1 fine sand,pot cement, lime, fireclay. Be careful with the lime, use a good quality hand barrier cream and or rubber gloves. Hurts like hell in a cut and dries out the skin on your hands otherwise.

[trockyh]

I'm using the home brew for my oven and it spreads and sticks well. I use rubber gloves so no problem with my hands. I bought one bag each of fire clay, portland and lime along with a yard of fine masons sand. Plenty to do the whole oven.

Tom