Lime mortar/ render

[gracie]

I have a whole heap of materials left around with which to finish my build. Next up is the entrance arch. I have enough firebricks for this but to be honest, I'd rather use something else because 1) they are expensive 2) they are maybe better kept for some unknown future project requiring firebrick, 3) they are really heavy and not sure that's best for the arch, 4) I'd like to avoid having to cut them.
i don't yet have any lime, and have only seen it available locally as a 25kg bag.
i do have the following...firebrick grog, fireclay powder, sand, cement, snowcrete white cement, sandstone walling blocks ( pictured )


Question is then, would the sandstone blocks be ok to use for the entrance arch? This will match the surrounding cladding and I think they could be cut with a bolster.
can I make an appropriate mortar with the materials listed? I like the idea of using a lime mortar and render ( for the dome once insulated and dry) but don't want to end up with another bag of stuff hardly used!

[cobblerdave]

G'day
I would not be using those firebrick for the entrance as firebrick is not built for outside and is not waterproof in the least. They will soak up water like crazy.
Those sandstone block could be used now that's as long as they are not cement based. If they are cement based they will break down in the heat. If you could get some common( no holes) house bricks they will do really well. You'll only need 12 or so.
Now that fireclay should do real well add that to some dried horse poo and you've got yourself a proper old school insulation layer and finish.
Regards dave

[gracie]

Thanks Dave, priceless advice. I'll keep an eye out for some reclaim bricks.

[annie]

Hi Gracie, find your local freecycle and advertise for some.

I have had lots of bits for free of these sites. The last being a dozen paving slabs. We had to pick them up mind (off steps), but it was a lot cheaper than buying them