Anybody build a concrete fire pit? Any problems with cracking?

[gatorgrizz27]

I've been interested in building a concrete fire pit like this one:

http://homemade-modern.com/ep46-concrete-fire-pit/

That guy used fire brick around the bottom, but I'm not sure it is necessary. People talk about an oxy acetylene torch making concrete pop and crack, but that is 3,500 degrees Celsius and a wood fire burns about 1,100 degrees Celcius.

I'm thinking about building it without a bottom, and just putting a layer of gravel in it. I would vibrate the concrete as I pour it to prevent any air pockets from forming.

Thanks for any input.

[Landrover]

my guy used fire brick for our gas unit but I doubt we use it enough (or long enough) to really matter.

[cbd10pt]

It will pop with a log fire!!!
Leave a hole through to the bare dirt ot leave a dead air space between pit and concrete

[cbd10pt]

You can use a cast iron or galvanized pipe to make a french drain for your pit if you go to bare dirt