Horticultural Vermiculite

[bookemdanno]

Taken from my Oven Build Thread..."I mixed up some Horticultural Vermiculite with some Lime for a pointing mix against the Oven Arch. Horticultural Verm is really fine 2-5mm grains, so it's like oatmeal when mixed.
I wanted something to hold the bricks, and seal externally, but attempt to keep a Thermal break. The inner section will have stove rope, as a sort of door seal too.

Whilst using the "Vermi-mortar" i wondered if this might help the workability of Vermicrete layers?
Maybe, by mixing in a quantity of this fine Vermiculite to building Vermiculite it'd increase the available surface area for the bits to bond together, thereby making it stick together slightly better.
Imagine making concrete from just 3/4 Stone as Vermicrete, and "All-in Ballast" as with Vermicrete "Fines" added.
I've no previous experience of Vermicrete, so someone whos done it before might prove a worthy Guinea Pig? As far as i can make out its the same product.

[faz]

Mixing small and large particle sizes will allow for tighter packing of vermiculite, which presumably means you can get away with less cement in the mix. This (in theory!!) might improve the insulating properties of the mix.

The main issue I can see is that it would be difficult to ensure consistent blending of the two types, as I am sure that the fines would settle to the bottom of the mixing bag. Whether this would actually be an issue is anyboy's guess! You're right, we need a guinea pig!

[tonyb]

As far as I am aware, all vermiculite sold, irrespective of marketing channel is the same stuff just different sizes and prices

For the vermicrete layer I'm pretty sure that we want big particles of vermiculite because of the entrapped air for insulation. Smaller particles will not be as efficient but as you say may increase workability.