Filling the gaps with mortar

[scottsummers]

Ok some I'm a newbie and have just finished the dome (see my build Scotty 36 sunshine coast, Australia) I'm not a master brick layer, I'm a helicopter pilot. Some of my joins on the oven side are not ideal, not terrible maybe 5mm gap here and there, can I just climb inside and use the same mortar to fill the gaps from the inside? I'm using a mix of fire clay/cement/lime/sand so far to stick the dome together. I have heard that cement can break down under xtreame heat, so would my planed mix work?!?
The mix is 10 sand/6 fire clay/3 lime/2 cement.
Thanks
Scotty

[david s]

The consensus seems to be that any breakdown of the Portland cement is compensated for by the lime.
The usual mix is sand, fireclay, lime, cement 3:1:1:1 Your brew is pretty close, but has more fireclay. Too much clay can create excessive shrinkage, but you should be ok.

[doctorphreak]

question about the heat could a person add more lime to the mix maybe like
3:1:2:1 to help with the heat more ?????