Plaster of Paris Failure Analysis

In a previous post on Zombie Engines I talked about this failed plaster brick.  It was

1:1 Plaster of Paris (POP) to Silica Flour (SF)
3:1 Water to Sodium Silicate (SS)
An unknown quantity of perlite


There are a lot of variables here but only two obvious questions.  First what caused the POP to form lumps when added to the liquid.  Second why did it crumble when dry.




Two test samples were prepared Sept 24, a week ago.   Both are 1:1: POP:SF.   The first is made with water and the second a 3:1 water:SS.

Both set up.  After several days both were ramped up to 450F and soaked for an hour in the toaster oven. Both are fine.   As usual the one with SS is softer.  I expect high heat would fix that.

So one would tend to blame the perlite.  More tests are required. Watch for the clumping, curdling.

The following will all include perlite
1. POP
2. POP with SF
3. POP with SF and SS (expected failure)

The run them all again and hydrate both the SF and the perlite.

to be continued after I have these test results.