Calcium silicate sheets for burn chamber?

Can these calcium silicate sheets be used as a liner for the burn chamber? They are 30mm thick.

I wanted to use ceramic fiber sheets but they are Just too expensive and i think both these materials can with stand similar temps

Hi Robert;
It depends on the temp rating.  I looked online and found 30mm Cs sheet rated @ 650C / 1200F
That is not high enough.  A j tube hits 1800F in the riser.  It would be less in the burn tunnel but not much.

Heavy firebrick should be a few bucks apiece,  I would use them for the entire core.  
In the feed tube, heavy brick is the only product to use.

Thanks again Thomas yeah i would hate to have to take it apart to rebuild. I will go with the firebrick. Is it possible to use the thinner slips of firebrick they are half the price?

Calcium  silicate will break down in the flame path but is fine to use behind brick.
You can definitely use half fire bricks for the firebox but you meed to support them from behind as they are to thin to self support themselves.
Whole fire bricks are easy to use especially  if you have access to a wet cut saw (hire one perhaps) then you can cut them to size.
Some folk dont bother to cut the bricks and manage to stick the bricks  together and get a working fire but it wont look pretty!
The disadvantage with whole bricks is the amount of time it will take to get the whole rocket fire unit up to temp, if you can use half bricks backed with insulation, the fire will perform better.
What do you intend to use for the heat riser?

I was thinking to either go for a fire brick riser or the ceramic blanket inside stove pipe. What do you consider the Best of these two?

If you can find and afford them, Insulated fire bricks (2600F-3000F) are the longest lasting.
Super wool runs a close second and is super fast and easy.