Rocks around fires

My experience from fire.....

Concrete (the cement dust) explodes like a firecracker (small but volatile) BUT only when directly exposed to very hot flame and through a roughed surface. A smooth surface normally found with concrete does not seem affected due to the chemical coating the water provides through screeding, but a broken piece or slag overburden can 'pop'.
The very hot flame needs to be concentrated like an oxy torch or similar but a 'normal' flame in a camp fire wouldn't be hot enough. Although it could be if another material was there that did get hot enough (like coal) in a concentrated area.
Volcanic rock explodes as stated due to trapped water. This can be quite a large explosion if the pocket is large enough and there is enough water trapped inside. A slowly heated rock would normally allow the water to evaporate naturally before any explosion occurred though, but if you chuck a cold rock in to a well lit fire, then you could have an issue.
Shale is the same due to trapped moisture.

We once had a smelting furnace "go up" quite literally due to water. The furnace had about 2 tonnes of molten steel and the roof was about 15 metres high. Straight through like it wasn't there then back down again.
It was caused by the electrical delivery circuit (water tubes) leaking under the furnace brickwork. The HOT steel made the leak worse then melted out through the crack in the furnace masonry onto a bed of leaked water. I was on top not much before it blew and you could see through the grating the metal leaking out. It was then that we took off and hadn't quite made it down the stairs before she went up. All due to water expanding and the only direction was up and all the steel (molten and otherwise) was lifted very quickly. I have learnt that water is powerful stuff.

One other thing about rocks around fires is they take a lot of time to cool down again causing a potential hazard to the next users and to vegetation that might blow into them. Water used to cool them off just may not be a good idea. Better to not use rocks for a simple camp fire anyway but mounds of dirt if you really need it.

That's my engineering point of view about explosions and fire anyway. My camping opinion is a little different as I use gas mostly.

Cheers Cam

Be carefull when arriving at a place that you can't see a fireplace, it may have been buried and the earth on top will be hot.

Each year people (mostly children) are burnt by walking over buried fires. Best to extinguish fire first before covering with dirt or sand. Buried fires can stay very hot for many hours. Parking a vehicle on top of a hidden hot fire might cause a few problems too.

Val.

As the other posters said.

If you're going to fill in a firepit, make sure it's been fully extinguished with water - literally saturated - and cold to the touch.

Burying a fire doesn't put it out.

Hi Wayne,

Nice set-up.

Tell me? You have 3 aerials. I'm guessing UHF and HF. What is the third one for??

Cheers

Alan

Alan,

At the time the photo was taken I had the two UHF aerials on the bull bar.

This photo shows how the set up is now with one UHF on the rear wheel carrier and one on the bull bar.

I have two UHF radios, one I use to talk to the convey and the other is on scan all the time to listen for other vehicles using UHF.

There is also another GPS aerial on the roof of the vehicle just in front of the wind deflector.

Image Could Not Be Found

Wayne

Ahh it all makes sense now.

Once again nice set-up

Regards

Sounds like a bit of a Furphy?Image Could Not Be Found

Hairy,

I was wondering how long it would take before someone worked out where it came from.

Wayne