Firebrick disaster?


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Old 03-15-05, 08:45 PM
J
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Firebrick disaster?

I am making a cinderblock BBQ lined with Fire Brick with an 1.5" airspace between the block and the bricks. I used type N mortar and mixed it with sand (as per instructions). However, what I did not do was pre-wet the bricks before laying them. Consequently, the fire bricks sucked up a lot of the mortar moisture and I fear that the bricks did not "set-up" very well (i.e., they did not seem to be sticking to the previously laid course. This was done two - three days ago and I have not done anything to the structure other than spray the interior down lightly with water at the end of the project. It is raining now and should rain for the next day or so... is it possible my fire bricks will end up holding after all or will I need to tear it down and start over?

One other note, after laying all the bricks, I went back and used a "finger" to finish out the joints. By and large, this tended to "compress" the mortar into place, but in other places, the mortar crumbled away (I fear because it dried out too quickly before the brick was set in place). I applied fresh mortar over the crumbled parts to "cover up" and seal the joint, but I am not sure how much actual "bonding" this did.

Any help would be greatly appreciated.
Thanks
 
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Old 03-16-05, 08:26 PM
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You should use Fire clay motar with the bricks, the Type N wont stand up tp the heat.
 
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Old 03-17-05, 09:42 AM
J
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Thanks Frank99.....

do you think I can go back over the "interior" (fireside) of the wall and "repoint" the joints with Fire Clay mortar... or do you think I need to tear the whole thing down and use Fire Clay mortar for the entire joint?

also what do you think the likelihood is that my bricks will set up properly given the conditions I previously described... do you think that although the fire bricks were laid dry they will form a good bond to each other? It has been raining for a day and a half here in Georgia and the mortar still appears a little bit green......

again thanks for your comments
 
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Old 03-17-05, 07:29 PM
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Check it out when it stops raining if you can't lift them off they probaly got a good bond, if your mortar was wetter than normal that would have helped you out.
I would just leave whats done alone and if you have to do more use the fire clay mortar, you might have to repoint the others down the road.
Bend a conduit,wet it and use it to strike the joints when your finger makes an impression.

Good Luck
Frank
 
  #5  
Old 03-19-05, 04:23 PM
Shanley
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I would rake out the mortar joints between 3/4" & 1" deep and repoint with refactory cement...You can but this at any masonry supply store or I beleive homedepot of lowes as well...What most likely will happen if you don't is the mortar will begin to breadown as soon as it exposed to the heat and begin to spall...you will see this happening rather quickly...I would also recommend that you slush (fill with mortar) the collar joint (airspace) between the brick and block...You should always back up firebrick with solid masonry
 
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Old 03-21-05, 03:31 PM
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Thanks

Thanks Shanley and Frank99. Since I need to use the BBQ in less than two weeks, I will likely let the Type N stand, but will "repair" the pit with refractory mortar at the first sign of spalling or crumbling (i.e., I will follow your advice Shanley at that time). FYI the bricks seem strong and have held. I was actually going to "Slush" the "collar joint" to give added support (this is a fire pit used for making coals to feed a separate pig cooker), because I feared that someone throwing a log on the fire might damage the wall. Also figured the heat transfer through the brick over the 14 hour period once a year that the cooker will experience will not adversely effect the slush or the cinderblock in the foreseeable future.

Again thanks for all of your help.
 
 

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