by hpmer » Tue Oct 22, 2013 12:27 am
I use it for my builds, but the others are right; ashes by themselves will pack down over time and lose their effectiveness. The way I use them is to mix them with a clay slip and then use them as the mix for the core build. They will fire over time just like brick and I've found they work pretty well.
I've only built a few of these things (5or 6) so it's a bit anecdotal, but so far am pleased with the results.
That said mine are cook stoves and are not used every day, so Matt may be right about longevity if you're planning on firing it every day for heat.
I'm currently building one of Matt's barrel bbq's so this one will get more of a workout, but I won't have results for a while, so that doesn't help you at present with your decision.