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View Full Version : Need advice for a cinder block pit


JonP
08-09-2016, 08:14 PM
BBQ Brethren,

I would like to build a cinder block pit much like Myron did on BBQ rules or Aaron Franklin did on his PBS show.

I have the space but ideally I would like to set it up over concrete because I have tons of space on a side yard. I've seen the exploding concrete posts, is there any way I can protect my concrete from exploding? Ie silica sand, sheet metal, fire brick, dirt. The slab was poured almost 20 years ago.

Thanks in advance

cowgirl
08-09-2016, 08:42 PM
I've not seen the pits you mentioned. All I can say is mine is built over dirt, and I don't build the cooking fire against the blocks.
A friend built one on a cement slab and his exploded, both the blocks and the cement.
Not sure how much heat the fire bricks would absorb... if they would keep the cement base from overheating or not.

If it were me, I wouldn't take the chance, I'd build it safe the first time round. jmo

3rd Grill
08-09-2016, 08:47 PM
JonP - Do some research on the word spalling. I'm not an engineer, but my understanding is that spalling happens when a small surface area is quickly heated to very hot temps. Whether or not a few inches of sand, dirt or other material will provide enough insulation to reduce the intensity of the heat that reaches the concrete underneath is something you'll have to decide.

Teleking
08-09-2016, 09:12 PM
JonP - Do some research on the word spalling. I'm not an engineer, but my understanding is that spalling happens when a small surface area is quickly heated to very hot temps. Whether or not a few inches of sand, dirt or other material will provide enough insulation to reduce the intensity of the heat that reaches the concrete underneath is something you'll have to decide.

Yep do your research because spalling can happen below zero and I don't pretend to be an engineer on weekends.

jeffturnerjr
08-09-2016, 10:50 PM
I don't know that I would risk it. Even if you were to put a foot of dirt, not sure that would even work.

mjpmap
08-10-2016, 06:40 AM
JonP - Do some research on the word spalling. I'm not an engineer, but my understanding is that spalling happens when a small surface area is quickly heated to very hot temps. Whether or not a few inches of sand, dirt or other material will provide enough insulation to reduce the intensity of the heat that reaches the concrete underneath is something you'll have to decide.

Back in the day, I investigated fires for a living. Spalling is almost guaranteed. It's nothing more than a steam explosion. The concrete will have a high moisture content even after "curing". When you put heat to it, water turns to steam, and the steam has no place to escape and............ Porous materials like fire brick allow the moisture to escape without pressure buildup so you don't have the same problem. Hope that helps.