[TheForge] Re: Question for Tom, Strengthening castable refractory

[Thomas A. Troszak]

> From: "David E. Smucker" <davesmucker@hotmail.com>
> Date: Fri, 22 Aug 2003 15:45:19 -0400
> Subject: [TheForge] Question for Tom, Strengthening castable refractory

> In building furnaces using castable refractory -- how have you done a "dry
> out" before going on to use under high fire?  What has worked for you?  How
> long have you let it air cure etc.?

Dear Dave,

I let the refractory air cure or about three days, depending on the weather,
then use a kerosene heater (the long cylindrical kind with the blower)
overnight, until the blocks look cooked. If I am precasting blocks that will
later be assembled, I stack them on a rack or pallet with stickers between
the blocks for air flow, then make a "tent" or "house' around the stack with
scraps of cement board (from the lumber yard) and prop the heater so that
the hot exhaust flows through the blocks. I usually let them cook until the
heater runs out of fuel (about 12 hours), the air temp coming out of the
cracks in the "tent" will be about 350 deg. F. by morning. The blocks are
now much lighter, indicating a significant loss of water.

Even after all that curing, they still steam upon the first few firings to
high temp, but I have never had one crack.

If the furnace is already assembled with green refractory, I park the heater
on a box or something so that the heated air blows in the open door of the
furnace, and try to keep the heat in as best as can be arranged.

Tom Troszak